LTC3586-3 [Linear Systems]
High Efficiency USB Power Manager with Boost; 与升压高效率USB电源管理器
| 型号： | LTC3586-3 |
| 厂家： | 
Linear Systems |
| 描述： | High Efficiency USB Power Manager with Boost |
| 文件： | 总36页 (文件大小：688K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
LTC3586-2/LTC3586-3
High Efficiency USB Power
Manager with Boost,
Buck-Boost and Dual Bucks
DESCRIPTION
FEATURES
Power Manager
The LTC®3586-2/LTC3586-3 are highly integrated power
management and battery charger ICs for Li-Ion/Polymer
battery applications. They include a high efficiency cur-
rentlimitedswitchingPowerPathmanagerwithautomatic
load prioritization, battery charger, ideal diode, and four
synchronous switching regulators (two bucks, one buck-
boost and one boost). Designed specifically for USB ap-
plications, the LTC3586-2/LTC3586-3’s switching power
manager automatically limits input current to a maximum
of either 100mA or 500mA for USB applications or 1A for
adapter-powered applications.
n
High Efficiency Switching PowerPath™ Controller
with Bat-Track™ Adaptive Output Control and
Instant-On Operation
n
Programmable USB or Wall Current Limit
(100mA/500mA/1A)
n
Full Featured Li-Ion/Polymer Battery Charger with
Float Voltage of 4.2V (LTC3586-2) or 4.1V
(LTC3586-3) with 1.5A Maximum Charge Current
n
Internal 180mΩ Ideal Diode Plus External Ideal Diode
Controller Powers Load in Battery Mode
n
<30µA No-Load Quiescent Current when Powered
Unlikelinearchargers,theLTC3586-2/LTC3586-3switching
architecturetransmitsnearlyallofthepoweravailablefrom
the USB port to the load with minimal loss and heat which
eases thermal constraints in small places. The two buck
regulators can provide up to 400mA each, the buck-boost
can deliver 1A, and the boost delivers at least 800mA.
from BAT
DC/DCs
n
Dual High Efficiency Buck DC/DCs (400mA I
)
OUT
)
n
n
n
n
High Efficiency Buck-Boost DC/DC (1A I
OUT
High Efficiency Boost DC/DC (800mA I
DC/DC FAULT Output
Compact (4mm × 6mm) 38-Pin QFN Package
)
OUT
The LTC3586-2/LTC3586-3 are available in a low profile
(0.75mm) 38-pin 4mm × 6mm QFN package.
APPLICATIONS
L, LT, LTC, LTM, Burst Mode, Linear Technology and the Linear logo are registered trademarks
and PowerPath and Bat-Track are trademarks of Linear Technology Corporation. All other
trademarks are the property of their respective owners. Protected by U.S. Patents including
6522118, 6404251.
n
Portable Medical/Industrial Devices
n
Other USB-Based Handheld Products
TYPICAL APPLICATION
High Efficiency PowerPath Manager, Dual Buck, Buck-Boost and Boost
Battery Charge Current vs
Battery Voltage (LTC3586-2)
USB/WALL
TO OTHER
LOADS
USB COMPLIANT
STEP-DOWN
4.5V TO 5.5V
REGULATOR
700
BATTERY CHARGE CURRENT
CC/CV
BATTERY
CHARGER
0V
OPTIONAL
Li-Ion
CURRENT
CONTROL
600
500
400
300
200
100
0
EXTRA CURRENT
FOR FASTER CHARGING
500mA USB CURRENT LIMIT
CHARGE
+
T
LTC3586-2/LTC3586-3
3.3V/20mA
RTC/LOW
ALWAYS ON LDO
POWER LOGIC
0.8V TO 3.6V/400mA
0.8V TO 3.6V/400mA
4
2
1
2
3
DUAL HIGH EFFICIENCY
MEMORY/
CORE µP
EN
MODE
BUCKS
V
= 5V
BUS
5x MODE
HIGH EFFICIENCY
BUCK-BOOST
BATTERY CHARGER PROGRAMMED FOR 1A
2.5V to 3.3V/1A
5V/800mA
I/O
SYSTEM
2.8
3.2 3.4 3.6
3.8
4
4.2
3
BATTERY VOLTAGE (V)
I
LIM
358623 TA01b
HIGH EFFICIENCY
BOOST
AUDIO/
MOTOR
4
FAULT
358623 TA01
358623f
1
LTC3586-2/LTC3586-3
ABSOLUTE MAXIMUM RATINGS
PIN CONFIGURATION
(Notes 1, 5)
TOP VIEW
V
(Transient) t < 1ms,
BUS
Duty Cycle < 1% ..........................................–0.3V to 7V
, V , V , V , V (Static),
V
38 37 36 35 34 33 32
IN1 IN2 IN3 IN4 BUS
I
I
1
2
3
4
5
6
7
8
9
31 GATE
LIM0
BAT, NTC, CHRG, FAULT, I
, I
,
LIM0 LIM1
30 CHRG
LIM1
EN3, EN4, MODE, FB4, V
.....................–0.3V to 6V
OUT4
LDO3V3
CLPROG
NTC
PROG
FB1
29
28
27
26
FB1...................–0.3V to Lesser of 6V and (V + 0.3V)
IN1
IN2
IN3
FB2...................–0.3V to Lesser of 6V and (V + 0.3V)
V
IN1
FB3, V ...........–0.3V to Lesser of 6V and (V + 0.3V)
V
SW1
C3
OUT4
39
GND
EN1, EN2................................–0.3V to Lesser of 6V and
V
OUT4
25 SW2
24
23 FB2
22
21 EN1
20
SW4
V
IN2
Max (V
V
BAT) + 0.3V
BUS, OUT,
MODE
I
I
I
I
I
I
I
....................................................................3mA
CLPROG
FB4 10
FB3 11
V
IN4
, I
...........................................................50mA
FAULT CHRG
........................................................................2mA
PROG
V
C3
12
EN2
...................................................................30mA
LDO3V3
13 14 15 16 17 18 19
UFE PACKAGE
, I
............................................................600mA
SW1 SW2
, I , I
............................................................2A
SW BAT VOUT
, I
, I
, I
...................................2.5A
SWAB3 SWCD3 SW4 VOUT3
38-LEAD (4mm × 6mm) PLASTIC QFN
Operating Temperature Range (Note 2)....–40°C to 85°C
Junction Temperature (Note 3) ............................. 125°C
Storage Temperature Range...................–65°C to 125°C
T
= 125°C, θ = 38.7°C/W
JMAX
JA
EXPOSED PAD (PIN 39) IS GND, MUST BE SOLDERED TO PCB
ORDER INFORMATION
LEAD FREE FINISH
LTC3586EUFE-2#PBF
LTC3586EUFE-3#PBF
TAPE AND REEL
PART MARKING
35862
PACKAGE DESCRIPTION
TEMPERATURE RANGE
LTC3586EUFE-2#TRPBF
LTC3586EUFE-3#TRPBF
–40°C to 85°C
–40°C to 85°C
38-Lead (4mm × 6mm) Plastic QFN
38-Lead (4mm × 6mm) Plastic QFN
35863
Consult LTC Marketing for parts specified with wider operating temperature ranges.
Consult LTC Marketing for information on non-standard lead based finish parts.
For more information on lead free part marking, go to: http://www.linear.com/leadfree/
For more information on tape and reel specifications, go to: http://www.linear.com/tapeandreel/
LTC3586 PRODUCT OPTIONS
BOOST OVERVOLTAGE
BOOST OVERVOLTAGE
OPTIONS
LTC3586
FLOAT VOLTAGE (V
)
FAULT PIN FUNCTIONALITY
Bi-Directional with Latch
Bi-Directional with Latch
Output Only, No Latch
THRESHOLD (V
)
HYSTERESIS (∆V
)
OV4
FLOAT
OV4
4.2V
4.1V
4.2V
4.1V
5.3V
5.3V
5.5V
5.5V
300mV
LTC3586-1
LTC3586-2
LTC3586-3
300mV
100mV
Output Only, No Latch
100mV
358623f
2
LTC3586-2/LTC3586-3
ELECTRICAL CHARACTERISTICS The l denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. VBUS = 5V, BAT = 3.8V, VIN1 = VIN2 = VIN3 = VIN4 = VOUT3 = 3.8V,
VOUT4 = 5V, RPROG = 1k, RCLPROG = 3.01k, unless otherwise noted.
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
PowerPath Switching Regulator
V
Input Supply Voltage
Total Input Current
4.35
5.5
V
BUS
l
l
l
l
I
1x Mode, V
5x Mode, V
= BAT
= BAT
OUT
87
95
100
500
1000
0.50
mA
mA
mA
mA
BUSLIM
OUT
OUT
436
800
0.31
460
860
0.38
10x Mode, V
= BAT
Suspend Mode, V
= BAT
OUT
I
V
Quiescent Current
1x Mode, I
5x Mode, I
= 0mA
= 0mA
7
15
mA
mA
mA
mA
VBUSQ
BUS
VOUT
VOUT
10x Mode, I
= 0mA
15
VOUT
Suspend Mode, I
= 0mA
0.044
VOUT
h
(Note 4) Ratio of Measured V
Current to
BUS
1x Mode
224
1133
2140
9.3
mA/mA
mA/mA
mA/mA
mA/mA
CLPROG
CLPROG Program Current
5x Mode
10x Mode
Suspend Mode
I
V
Current Available Before Loading 1x Mode, BAT = 3.3V
5x Mode, BAT = 3.3V
135
672
1251
0.32
mA
mA
mA
mA
OUT(POWERPATH)
OUT
BAT
10x Mode, BAT = 3.3V
Suspend Mode
V
V
V
V
CLPROG Servo Voltage in Current Limit 1x, 5x, 10x Modes
Suspend Mode
1.188
100
V
CLPROG
mV
V
Undervoltage Lockout
Rising Threshold
Falling Threshold
4.30
4.00
4.35
V
V
UVLO_VBUS
UVLO_VBUS-BAT
OUT
BUS
3.95
V
to BAT Differential Undervoltage
Rising Threshold
Falling Threshold
200
50
mV
mV
BUS
Lockout
V
Voltage
1x, 5x, 10x Modes, 0V < BAT < 4.2V,
VOUT
3.5 BAT + 0.3 4.7
V
OUT
I
= 0mA, Battery Charger Off
USB Suspend Mode, I
= 250µA
4.5
1.8
4.6
4.7
2.7
V
MHz
Ω
VOUT
f
Switching Frequency
2.25
0.18
0.30
OSC
R
R
PMOS On-Resistance
PMOS_POWERPATH
NMOS_POWERPATH
PEAK_POWERPATH
NMOS On-Resistance
Ω
I
Peak Switch Current Limit (Note 5)
1x, 5x Modes
10x Mode
2
3
A
A
Battery Charger
V
FLOAT
BAT Regulated Output Voltage
LTC3586-2
LTC3586-2
LTC3586-3
LTC3586-3
4.179
4.165
4.079
4.065
4.200
4.200
4.100
4.100
4.221
4.235
4.121
4.135
V
V
V
V
l
l
I
I
Constant-Current Mode Charge Current
Battery Drain Current
R
R
= 1k
= 5k
980
185
1022
204
1065
223
mA
mA
CHG
PROG
PROG
V
BUS
V
BUS
> V
, I = 0µA
VOUT
2
3.5
29
5
41
µA
µA
BAT
UVLO VOUT
= 0V, I
= 0µA (Ideal Diode Mode)
V
V
PROG Pin Servo Voltage
1.000
0.100
V
V
PROG
PROG Pin Servo Voltage in Trickle
Charge
BAT < V
BAT < V
PROG_TRKL
TRKL
V
C/10 Threshold Voltage at PROG
100
1022
100
mV
mA/mA
mA
C/10
PROG
TRKL
h
Ratio of I to PROG Pin Current
BAT
I
Trickle Charge Current
TRKL
358623f
3
LTC3586-2/LTC3586-3
ELECTRICAL CHARACTERISTICS The l denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. VBUS = 5V, BAT = 3.8V, VIN1 = VIN2 = VIN3 = VIN4 = VOUT3 = 3.8V,
VOUT4 = 5V, RPROG = 1k, RCLPROG = 3.01k, unless otherwise noted.
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
2.85
130
–100
4
MAX
UNITS
V
V
Trickle Charge Threshold Voltage
Trickle Charge Hysteresis Voltage
Recharge Battery Threshold Voltage
Safety Timer Termination
BAT Rising
2.7
3.0
TRKL
∆V
mV
TRKL
RECHRG
TERM
V
Threshold Voltage Relative to V
–75
3.3
–125
5
mV
FLOAT
t
t
Timer Starts When BAT = V
Hour
Hour
mA/mA
mV
FLOAT
Bad Battery Termination Time
BAT < V
0.42
0.088
0.5
0.63
0.112
100
1
BADBAT
TRKL
h
C/10
End-of-Charge Indication Current Ratio (Note 6)
0.1
V
CHRG Pin Output Low Voltage
CHRG Pin Leakage Current
Battery Charger Power FET
I
= 5mA
= 5V
65
CHRG
CHRG
CHRG
I
V
µA
CHRG
R
0.18
110
Ω
ON_CHG
On-Resistance (Between V
and BAT)
OUT
T
Junction Temperature in Constant
Temperature Mode
°C
LIM
NTC
V
COLD
V
HOT
V
DIS
Cold Temperature Fault Threshold
Voltage
Rising Threshold
Hysteresis
75.0
33.4
0.7
76.5
1.5
78.0
36.4
2.7
%V
%V
BUS
BUS
Hot Temperature Fault Threshold
Voltage
Falling Threshold
Hysteresis
34.9
1.73
%V
%V
BUS
BUS
NTC Disable Threshold Voltage
Falling Threshold
Hysteresis
1.7
50
%V
BUS
mV
I
NTC Leakage Current
V
= V = 5V
BUS
–50
50
nA
NTC
NTC
Ideal Diode
V
Forward Voltage
V
VOUT
= 0V, I
= 10mA
= 0V
BUS
= 10mA
2
mV
mV
FWD
BUS
VOUT
I
15
R
Internal Diode On-Resistance, Dropout
Internal Diode Current Limit
V
0.18
Ω
A
DROPOUT
I
1.6
3.1
MAX_DIODE
Always On 3.3V Supply
V
Regulated Output Voltage
0mA < I
< 20mA
LDO3V3
3.3
4
3.5
0.4
100
V
Ω
Ω
LDO3V3
R
R
Closed-Loop Output Resistance
Dropout Output Resistance
CL_LDO3V3
23
OL_LDO3V3
Logic Input (EN1, EN2, EN3, EN4, MODE, ILIM0, ILIM1)
V
IL
V
IH
Logic Low Input Voltage
Logic High Input Voltage
Pull-Down Current
V
V
1.2
I
PD
1
µA
FAULT Output
V
FAULT
FAULT Pin Output Low Voltage
FAULT Delay
I
= 5mA
FAULT
65
14
mV
ms
V
FBx Voltage Threshold
for FAULT (x = 1, 2, 3, 4)
0.736
358623f
4
LTC3586-2/LTC3586-3
ELECTRICAL CHARACTERISTICS The l denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. VBUS = 5V, BAT = 3.8V, VIN1 = VIN2 = VIN3 = VIN4 = VOUT3 = 3.8V,
VOUT4 = 5V, RPROG = 1k, RCLPROG = 3.01k, unless otherwise noted.
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
Switching Regulators 1, 2, 3 and 4
V
V
Input Supply Voltage
2.7
2.5
5.5
2.9
V
IN1,2,3,4
V
OUT
V
OUT
UVLO—V
UVLO—V
Falling
Rising
V
Connected to V Through
OUT
2.6
2.8
V
V
OUTUVLO
OUT
OUT
IN1,2,3,4
Low Impedance. Switching Regulators
are Disabled in UVLO
f
I
Oscillator Frequency
FBx Input Current
1.8
–50
0.78
2.25
0.80
2.7
50
MHz
nA
V
OSC
V
= 0.85V
FB1,2,3,4
FB1,2,3,4
l
V
V
Servo Voltage
FBx
0.82
FB1,2,3,4
Switching Regulators 1 and 2 (Buck)
I
Pulse-Skipping Mode Input Current
Burst Mode® Input Current
Shutdown Input Current
I
I
I
= 0µA, (Note 7)
= 0µA, (Note 7)
= 0µA, (Note 7)
225
35
µA
µA
µA
VIN1,2
VOUT1,2
VOUT1,2
VOUT1,2
60
1
I
PMOS Switch Current Limit
Pulse-Skipping/Burst Mode Operation (Note 5)
600
100
800
0.6
0.7
1100
mA
Ω
LIM1,2
R
R
D
R
PMOS R
NMOS R
P1,2
N1,2
1,2
DS(ON)
DS(ON)
Ω
Maximum Duty Cycle
%
SW1,2 Pull-Down in Shutdown
10
kΩ
SW1,2
Switching Regulator 3 (Buck-Boost)
I
Input Current
PWM Mode, I
= 0µA
VOUT3
220
13
0
400
20
1
µA
µA
µA
VIN3
Burst Mode Operation, I
Shutdown
= 0µA
VOUT3
V
V
Minimum Regulated Output Voltage
Maximum Regulated Output Voltage
Forward Current Limit (Switch A)
For Burst Mode Operation or PWM Mode
2.65
5.6
2.5
275
0
2.75
V
V
OUT3(LOW)
OUT3(HIGH)
LIMF3
5.5
2
l
l
l
I
I
I
I
PWM Mode (Note 5)
3
A
Forward Burst Current Limit (Switch A) Burst Mode Operation
Reverse Burst Current Limit (Switch D) Burst Mode Operation
200
–30
50
350
30
mA
mA
mA
PEAK3(BURST)
ZERO3(BURST)
MAX3(BURST)
Maximum Deliverable Output Current in 2.7V ≤ V ≤ 5.5V, 2.75V ≤ V
Burst Mode Operation
≤ 5.5V
OUT3
IN3
(Note 8)
R
R
PMOS R
NMOS R
Switches A, D
Switches B, C
Switches A, D
Switches B, C
0.22
0.17
Ω
Ω
DS(ON)P
DS(ON)N
LEAK(P)
LEAK(N)
DS(ON)
DS(ON)
I
I
PMOS Switch Leakage
NMOS Switch Leakage
–1
–1
1
1
µA
µA
kΩ
%
R
D
D
V
Pull-Down in Shutdown
OUT3
10
VOUT3
l
Maximum Buck Duty Cycle
Maximum Boost Duty Cycle
Soft-Start Time
PWM Mode
PWM Mode
100
BUCK(MAX)
BOOST(MAX)
75
%
t
0.5
ms
SS3
358623f
5
LTC3586-2/LTC3586-3
ELECTRICAL CHARACTERISTICS The l denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. VBUS = 5V, BAT = 3.8V, VIN1 = VIN2 = VIN3 = VIN4 = VOUT3 = 3.8V,
VOUT4 = 5V, RPROG = 1k, RCLPROG = 3.01k, unless otherwise noted.
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
Switching Regulator 4 (Boost)
I
Input Current
FB4 > 0.8V, I
Shutdown, V
= 0µA
VOUT4
OUT4
180
µA
µA
VIN4
= 0V
1
I
I
Q-Current Drawn from Boost Output
NMOS Switch Current Limit
Output Voltage Adjust Range
Overvoltage Shutdown
FB4 = 0V
(Note 5)
7.5
mA
mA
V
VOUT4
2000
5.3
2800
LIMF4
V
V
5
OUT4
5.5
0.1
5.7
V
OV4
∆V
Overvoltage Shutdown Hysteresis
V
OV4
R
R
PMOS R
NMOS R
Synchronous Switch
Main Switch
0.25
0.17
Ω
DS(ON)P4
DS(ON)N4
LEAK(P)4
LEAK(N)4
DS(ON)
DS(ON)
Ω
I
I
PMOS Switch Leakage
NMOS Switch Leakage
Synchronous Switch
Main Switch
–1
–1
1
1
µA
µA
kΩ
%
R
D
V
Pull-Down in Shutdown
OUT4
10
91
VOUT4
Maximum Boost Duty Cycle
Soft-Start Time
94
BOOST(MAX)
t
0.375
ms
SS4
Note 1: Stresses beyond those listed under Absolute Maximum Ratings
may cause permanent damage to the device. Exposure to any Absolute
Maximum Rating condition for extended periods may affect device
reliability and lifetime.
Note 2: The LTC3586E-2/LTC3586E-3 are guaranteed to meet performance
specifications from 0°C to 85°C. Specifications over the –40°C to 85°C
operating temperature range are assured by design, characterization and
correlation with statistical process controls.
Note 4: Total input current is the sum of quiescent current, I
measured current given by:
, and
VBUSQ
V
/R
• (h
+1)
CLPROG CLPROG
CLPROG
Note 5: The current limit features of this part are intended to protect the
IC from short term or intermittent fault conditions. Continuous operation
above the maximum specified pin current rating may result in device
degradation or failure.
Note 6: h
is expressed as a fraction of measured full charge current
C/10
Note 3: The LTC3586E-2/LTC3586E-3 include overtemperature protection
that is intended to protect the device during momentary overload
conditions. Junction temperature will exceed 125°C when overtemperature
protection is active. Continuous operation above the specified maximum
operating junction temperature may impair device reliability.
with indicated PROG resistor.
Note 7: FBx above regulation such that regulator is in sleep. Specification
does not include resistive divider current reflected back to V
Note 8: Guaranteed by design.
.
INX
358623f
6
LTC3586-2/LTC3586-3
(TA = 25°C unless otherwise noted)
TYPICAL PERFORMANCE CHARACTERISTICS
Output Voltage vs Output Current
(Battery Charger Disabled)
Ideal Diode Resistance
Ideal Diode V-I Characteristics
vs Battery Voltage
1.0
0.8
0.6
0.4
0.2
0
0.25
0.20
0.15
0.10
0.05
0
4.50
V
= 5V
INTERNAL IDEAL DIODE
WITH SUPPLEMENTAL
EXTERNAL VISHAY
Si2333 PMOS
BUS
BAT = 4V
5x MODE
4.25
4.00
3.75
3.50
3.25
INTERNAL IDEAL DIODE
INTERNAL IDEAL
DIODE ONLY
BAT = 3.4V
INTERNAL IDEAL DIODE
WITH SUPPLEMENTAL
EXTERNAL VISHAY
Si2333 PMOS
V
V
= 0V
= 5V
BUS
BUS
0
0.04
0.08
0.12
0.16
0.20
2.7
3.0
3.3
3.6
3.9
4.2
0
200
400
600
800
1000
FORWARD VOLTAGE (V)
BATTERY VOLTAGE (V)
OUTPUT CURRENT (mA)
358623 G01
358623 G02
358623 G03
USB Limited Battery Charge
Current vs Battery Voltage
USB Limited Battery Charge
Current vs Battery Voltage
Battery Drain Current
vs Battery Voltage
25
20
15
10
5
150
125
700
600
I
= 0µA
VOUT
LTC3586-2
LTC3586-2
V
= 0V
BUS
V
R
R
= 5V
BUS
500
400
300
200
100
0
100
75
= 1k
PROG
CLPROG
= 3k
LTC3586-3
LTC3586-3
50
25
0
V
R
R
= 5V
BUS
V
= 5V
BUS
= 1k
PROG
CLPROG
(SUSPEND MODE, R
= 3.01k)
3.9
CLPROG
= 3k
1x USB SETTING,
BATTERY CHARGER SET FOR 1A
5x USB SETTING,
BATTERY CHARGER SET FOR 1A
0
2.7
3.0
3.3
3.6
4.2
3.0 3.3 3.6
BATTERY VOLTAGE (V)
4.2
2.7
3.9
2.7 3.0 3.3 3.6
BATTERY VOLTAGE (V)
3.9
4.2
BATTERY VOLTAGE (V)
358623 G06
358623 G04
358623 G05
Battery Charging Efficiency vs
Battery Voltage with No External
PowerPath Switching Regulator
Efficiency vs Output Current
Load (PBAT/PBUS
)
100
90
80
70
60
50
40
100
90
80
70
60
BAT = 3.8V
5x, 10x MODE
1x MODE
1x CHARGING EFFICIENCY
5x CHARGING EFFICIENCY
R
R
= 3.01k
CLPROG
= 1k
PROG
I
= 0mA
VOUT
3.5
BATTERY VOLTAGE (V)
0.01
0.1
1
2.7
3
3.9
4.2
3.3
OUTPUT CURRENT (A)
358623 G07
358623 G08
358623f
7
LTC3586-2/LTC3586-3
(TA = 25°C unless otherwise noted)
TYPICAL PERFORMANCE CHARACTERISTICS
VBUS Current vs VBUS Voltage
(Suspend)
Output Voltage vs Output Current
in Suspend
V
BUS Current vs Output Current in
Suspend
45
40
35
30
25
20
15
10
5
5.0
4.5
4.0
3.5
3.0
2.5
0.5
0.4
0.3
0.2
0.1
0
V
= 5V
BUS
BAT = 3.3V
= 3.01k
R
CLPROG
V
BUS
= 5V
BAT = 3.3V
= 3.01k
R
CLPROG
0
0
1
2
3
4
5
0
0.1
0.2
0.3
0.4
0.5
0
0.1
0.3
OUTPUT CURRENT (mA)
0.4
0.5
0.2
V
VOLTAGE (V)
OUTPUT CURRENT (mA)
BUS
358623 G09
358623 G10
358623 G11
3.3V LDO Output Voltage
vs Output Current, VBUS = 0V
Battery Charge Current
vs Temperature
Battery Charger Float Voltage
vs Temperature
3.4
3.2
3.0
2.8
2.6
4.21
4.20
4.19
4.18
4.17
600
500
400
300
200
100
0
BAT = 3.5V
BAT = 3.9V, 4.2V
BAT = 3.4V
BAT = 3.6V
THERMAL REGULATION
BAT = 3V
BAT = 3.1V
BAT = 3.2V
R
= 2k
PROG
BAT = 3.3V
10x MODE
60 80
20 40
TEMPERATURE (°C)
–40 –20
0
100 120
0
5
10
15
20
25
–40
–15
10
35
60
85
OUTPUT CURRENT (mA)
TEMPERATURE (°C)
358623 G13
358623 G12
358623 G14
Oscillator Frequency
vs Temperature
Low Battery (Instant On) Output
Voltage vs Temperature
3.68
3.66
3.64
3.62
3.60
2.6
2.4
2.2
2.0
1.8
BAT = 2.7V
I
= 100mA
VOUT
5x MODE
BAT = 3.6V
= 0V
V
= 5V
BUS
V
BUS
BAT = 3V
= 0V
V
BUS
BAT = 2.7V
= 0V
V
BUS
–40
–15
10
35
60
85
–40
–15
10
35
60
85
TEMPERATURE (°C)
TEMPERATURE (°C)
358623 G15
358623 G16
358623f
8
LTC3586-2/LTC3586-3
TYPICAL PERFORMANCE CHARACTERISTICS (TA = 25°C unless otherwise noted)
V
BUS Quiescent Current in
VBUS Quiescent Current
vs Temperature
CHRG Pin Current vs Voltage
(Pull-Down State)
Suspend vs Temperature
70
60
50
40
30
100
15
12
9
V = 5V
BUS
I
= 0µA
V
VOUT
= 5V
VOUT
BUS
BAT = 3.8V
I
= 0µA
5x MODE
80
60
40
20
0
1x MODE
6
3
–40
–15
10
35
60
85
0
1
2
3
4
5
–40
–15
10
35
60
85
TEMPERATURE (°C)
CHRG PIN VOLTAGE (V)
TEMPERATURE (°C)
358623 G18
358623 G19
358623 G17
3.3V LDO Step Response
(5mA to 15mA)
Battery Drain Current
vs Temperature
Switching Regulators 1, 2 Pulse-
Skipping Mode Quiescent Currents
50
40
30
20
10
0
325
300
275
250
225
200
1.95
1.90
1.85
1.80
1.75
1.70
BAT = 3.8V
V
= 3.8V
IN1,2
V
= 0V
BUS
ALL REGULATORS OFF
I
LDO3V3
5mA/DIV
V
= 2.5V
OUT1,2
(CONSTANT FREQUENCY)
0mA
V
LDO3V3
20mV/DIV
AC-
COUPLED
358623 G20
BAT = 3.8V
20µs/DIV
V
= 1.25V
OUT1,2
(PULSE SKIPPING)
–40
–15
10
35
60
85
–40
–15
10
35
60
85
TEMPERATURE (°C)
TEMPERATURE (°C)
358623 G21
358623 G22
Switching Regulators 1, 2
Pulse-Skipping Mode Efficiency
Switching Regulators 1, 2
Burst Mode Efficiency
100
90
100
90
80
70
60
50
40
30
20
10
0
V
= 2.5V
OUT1,2
V
= 2.5V
OUT1,2
80
V
= 1.2V
OUT1,2
V
= 1.2V
OUT1,2
70
V
OUT1,2
= 1.8V
V
= 1.8V
OUT1,2
60
50
40
30
20
10
0
V
= 3.8V
V
= 3.8V
IN1,2
IN1,2
1
10
100
1000
0.1
1
10
100
1000
OUTPUT CURRENT (mA)
OUTPUT CURRENT (mA)
358623 G23
358623 G24
358623f
9
LTC3586-2/LTC3586-3
(TA = 25°C unless otherwise noted.)
TYPICAL PERFORMANCE CHARACTERISTICS
Switching Regulators 1, 2 Load
Regulation at VOUT1, 2 = 1.2V
Switching Regulators 1, 2 Load
Regulation at VOUT1, 2 = 1.8V
Switching Regulators 1, 2 Load
Regulation at VOUT1, 2 = 2.5V
1.230
1.215
1.200
1.845
1.823
1.800
2.56
2.53
2.50
V
= 3.8V
V
= 3.8V
V
= 3.8V
BUS
BUS
BUS
Burst Mode
OPERATION
Burst Mode OPERATION
PULSE-SKIPPING MODE
Burst Mode OPERATION
PULSE-SKIPPING MODE
PULSE-SKIPPING
MODE
1.185
1.170
1.778
1.755
2.47
2.44
0.1
1
10
100
1000
0.1
1
10
100
1000
0.1
1
10
100
1000
OUTPUT CURRENT (mA)
OUTPUT CURRENT (mA)
OUTPUT CURRENT (mA)
358623 G25
358623 G26
358623 G27
Buck-Boost Regulator Forward
Current Limit
Buck-Boost Regulator Efficiency
vs ILOAD
RDS(ON) For Buck-Boost Regulator
100
90
80
70
60
50
40
30
20
10
0
0.30
0.25
0.40
0.35
2600
2550
V
= 3V
IN3
PMOS V = 3V
IN3
PMOS V = 3.6V
IN3
Burst Mode
PMOS V = 4.5V
IN3
OPERATION
V
= 3.6V
= 4.5V
PWM MODE
IN3
IN3
CURVES
CURVES
0.20
0.30
2500
V
V
V
= 3V
= 3.6V
= 4.5V
V
IN3
IN3
IN3
V
V
V
= 3V
= 3.6V
= 4.5V
IN3
IN3
IN3
NMOS V = 3V
IN3
0.15
0.10
0.25
0.20
2450
2400
NMOS V = 3.6V
IN3
NMOS V = 4.5V
IN3
0.05
0
0.15
0.10
2350
2300
V
= 3.3V
OUT3
TYPE 3 COMPENSATION
0.1
1
10 100 1000
–55 –35 –15
5
25 45 65
85 105
125
–55 –35 –15
5
25 45 65 85 105 125
I
(mA)
TEMPERATURE (°C)
TEMPERATURE (°C)
LOAD
358623 G28
358623 G29
358623 G30
Buck-Boost Regulator Burst Mode
Operation Quiescent Current
Reduction in Current
Deliverability at Low VIN3
14.0
13.5
300
250
STEADY-STATE I
START-UP WITH A
RESISTIVE LOAD
START-UP WITH A
CURRENT SOURCE LOAD
LOAD
V
= 4.5V
IN3
13.0
200
150
V
= 3V
IN1
V
= 3.6V
IN3
12.5
12.0
100
50
0
11.5
11.0
V
= 3.3V
OUT3
TYPE 3 COMPENSATION
2.7
3.1
3.5
3.9
(V)
4.3
4.7
–55 –35 –15
5
25 45 65 85 105 125
TEMPERATURE (°C)
V
IN3
358623 G32
358623 G31
358623f
10
LTC3586-2/LTC3586-3
(TA = 25°C unless otherwise noted.)
TYPICAL PERFORMANCE CHARACTERISTICS
Boost Efficiency vs VIN4
Buck-Boost Step Response
Boost Efficiency (VIN4 = 3.8V)
100
90
80
70
60
50
40
30
20
10
0
100
90
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
V
= 5V
OUT4
V
OUT3
100mV/DIV
AC-
80
COUPLED
70
EFFICIENCY
60
50
SYNCH
PMOS
OFF
300mA
POWER LOSS
I
VOUT3
40
30
20
10
0
200mA/DIV
0
358623 G33
100µs/DIV
V
V
= 3.8V
OUT3
IN3
I
= 300mA
= 5V
VOUT4
= 3.3V
V
OUT4
2.6
3
3.4 3.8 4.2 4.6
INPUT VOLTAGE V (V)
5
5.4
1
10
100
(mA)
1000
I
IN4
VOUT4
358623 G23
358623 G35
Maximum Deliverable Boost
Output Current
Boost Output Voltage
vs Temperature
5.000
4.995
4.990
4.985
4.980
4.975
4.970
4.965
4.960
4.955
4.950
2200
2000
1800
1600
1400
1200
1000
800
L = 2.2µH
OUT4
V
= 4.9V (SET FOR 5V)
V
= 2.7V
IN4
V
= 4.5V
IN4
T = –45°C
T = 90°C
T = 25°C
V
= 3.8V
IN4
600
400
200
0
–45 –30 –15
0
15 30 45 60 75 90
2.7
3
3.3
3.6
(V)
3.9
4.2
4.5
TEMPERATURE (°C)
V
IN4
358623 G36
358623 G37
Maximum Boost Duty Cycle
vs VIN4
Boost Step Response
(50mA to 300mA)
100
95
V
OUT4
100mV/DIV
T = 90°C
T = 25°C
AC-
COUPLED
90
85
80
T = –45°C
300mA
I
VOUT4
125mA/DIV
50mA
358623 G39
V
V
= 3.8V
OUT4
50µs/DIV
IN4
= 5V
L = 2.2µH
C = 10µF
2.7
3
3.3
3.6
(V)
3.9
4.2
4.5
V
IN4
358623 G38
358623f
11
LTC3586-2/LTC3586-3
PIN FUNCTIONS
I
, I
(Pins 1, 2): Logic Inputs. I
and I
LIM1
SW4 (Pin 8): Switch Node for the (Boost) Switching
LIM0 LIM1
LIM0
control the current limit of the PowerPath switching
Regulator 4. An external inductor connects between this
regulator. See Table 1.
pin and V
.
IN4
MODE (Pin 9): Digital Input. The MODE pin controls dif-
ferent modes of operation for the switching regulators
according to Table 2.
Table 1. USB Current Limit Settings
(I
LIM1
)
(I
)
USB SETTING
LIM0
0
0
1x Mode (USB 100mA Limit)
10x Mode (Wall 1A Limit)
Suspend
0
1
1
1
0
1
Table 2. Switching Regulators Mode
REGULATION MODE
5x Mode (USB 500mA Limit)
Mode
Buck
Pulse Skipping
Burst
Buck-Boost
PWM
Boost
0
1
Pulse Skipping
Pulse Skipping
LDO3V3 (Pin 3): 3.3V LDO Output Pin. This pin provides
Burst
a regulated always-on 3.3V supply voltage. LDO3V3
gets its power from V . It may be used for light loads
OUT
FB4 (Pin 10): Feedback Input for the (Boost) Switching
Regulator 4. When the control loop is complete, the volt-
age on this pin servos to 0.8V.
such as a watch dog microprocessor or real time clock.
A 1µF capacitor is required from LDO3V3 to ground. If
the LDO3V3 output is not used it should be disabled by
FB3 (Pin 11): Feedback Input for (Buck-Boost) Switching
Regulator 3. When regulator 3’s control loop is complete,
this pin servos to 0.8V.
connecting it to V
.
OUT
CLPROG (Pin 4): USB Current Limit Program and Moni-
tor Pin. A resistor from CLPROG to ground determines
V (Pin12):OutputoftheErrorAmplifierandVoltageCom-
C3
the upper limit of the current drawn from the V
pin.
BUS
pensation Node for (Buck-Boost) Switching Regulator 3.
ExternalTypeIorTypeIIIcompensation(toFB3)connects
to this pin. See the Applications Information section for
selecting buck-boost compensation components.
A fraction of the V
current is sent to the CLPROG pin
BUS
when thesynchronous switchofthePowerPath switching
regulatorison.Theswitchingregulatordeliverspoweruntil
theCLPROGpinreaches1.188V.SeveralV currentlimit
BUS
settings are available via user input which will typically
correspond to the 500mA and 100mA USB specifications.
A multilayer ceramic averaging capacitor is required at
CLPROG for filtering.
SWAB3 (Pin 13): Switch Node for (Buck-Boost) Switch-
ing Regulator 3. Connected to Internal Power Switches A
and B. An external inductor connects between this node
and SWCD3.
NTC (Pin 5): Input to the Thermistor Monitoring Circuits.
The NTC pin connects to a battery’s thermistor to deter-
mine if the battery is too hot or too cold to charge. If the
battery’s temperature is out of range, charging is paused
until it re-enters the valid range. A low drift bias resistor
V
(Pins14,15):PowerInputfor(Buck-Boost)Switching
IN3
Regulator3.ThesepinswillgenerallybeconnectedtoV
.
OUT
A 1µF MLCC capacitor is recommended on these pins.
V
(Pins 16, 17): Output Voltage for (Buck-Boost)
OUT3
Switching Regulator 3.
is required from V
to NTC and a thermistor is required
BUS
from NTC to ground. If the NTC function is not desired,
the NTC pin should be grounded.
EN3 (Pin 18): Digital Input. This input enables the
buck-boost switching regulator 3.
V
(Pins 6, 7): Power Output for the (Boost) Switching
SWCD3 (Pin 19): Switch Node for (Buck-Boost) Switch-
ing Regulator 3 Connected to Internal Power Switches C
and D. An external inductor connects between this node
and SWAB3.
OUT4
Regulator 4. A 10µF MLCC capacitor should be placed as
close to the pins as possible.
358623f
12
LTC3586-2/LTC3586-3
PIN FUNCTIONS
EN2 (Pin 20): Digital Input. This input enables the buck
GATE (Pin 31): Analog Output. This pin controls the gate
switching regulator 2.
of an optional external P-channel MOSFET transistor used
to supplement the ideal diode between V
and BAT. The
OUT
EN1 (Pin 21): Digital Input. This input enables the buck
switching regulator 1.
external ideal diode operates in parallel with the internal
ideal diode. The source of the P-channel MOSFET should
V
(Pin 22): Power Input for Switching Regulator 4
IN4
be connected to V
and the drain should be connected
OUT
(Boost). This pin will generally be connected to V
.
OUT
to BAT. If the external ideal diode FET is not used, GATE
should be left floating.
A 1µF MLCC capacitor is recommended on this pin.
FB2 (Pin 23): Feedback Input for (Buck) Switching Regu-
lator 2. When regulator 2’s control loop is complete, this
pin servos to 0.8V.
BAT (Pin 32): Single Cell Li-Ion Battery Pin. Depending on
available V
power, a Li-Ion battery on BAT will either
BUS
deliverpowertoV throughtheidealdiodeorbecharged
OUT
from V
via the battery charger.
OUT
V
(Pin 24): Power Input for (Buck) Switching Regu-
IN2
lator 2. This pin will generally be connected to V
.
OUT
EN4 (Pin 33): Digital Input. This input enables the boost
switching regulator 4.
A 1µF MLCC capacitor is recommended on this pin.
SW2 (Pin 25): Power Transmission Pin for (Buck) Switch-
V
(Pin34):OutputVoltageoftheSwitchingPowerPath
OUT
ing Regulator 2.
Controller and Input Voltage of the Battery Charger. The
majority of the portable product should be powered from
SW1 (Pin 26): Power Transmission Pin for (Buck) Switch-
ing Regulator 1.
V
.TheLTC3586-2/LTC3586-3willpartitiontheavailable
OUT
power between the external load on V
and the internal
OUT
V
(Pin 27): Power Input for (Buck) Switching Regula-
IN1
battery charger. Priority is given to the external load and
any extra power is used to charge the battery. An ideal
tor 1. This pin will generally be connected to V . A 1µF
OUT
MLCC capacitor is recommended on this pin.
diodefromBATtoV
ensuresthatV
ispoweredeven
OUT
OUT
if the load exceeds the allotted power from V
or if the
FB1 (Pin 28): Feedback Input for (Buck) Switching Regu-
lator 1. When regulator 1’s control loop is complete, this
pin servos to 0.8V.
BUS
V
power source is removed. V
should be bypassed
BUS
OUT
with a low impedance ceramic capacitor.
V
(Pins 35, 36): Primary Input Power Pin. These
PROG (Pin 29): Charge Current Program and Charge
Current Monitor Pin. Connecting a resistor from PROG
to ground programs the charge current. If sufficient in-
put power is available in constant-current mode, this pin
servos to 1V. The voltage on this pin always represents
the actual charge current.
BUS
pins deliver power to V
via the SW pin by drawing
OUT
controlled current from a DC source such as a USB port
or wall adapter.
SW (Pin 37): Power Transmission Pin for the USB
PowerPath. TheSWpindeliverspowerfromV
toV
BUS
OUT
via the buck switching regulator. A 3.3µH inductor should
CHRG (Pin 30): Open-Drain Charge Status Output. The
CHRG pin indicates the status of the battery charger. Four
possible states are represented by CHRG: charging, not
charging, unresponsive battery and battery temperature
out of range. CHRG is modulated at 35kHz and switches
between a low and a high duty cycle for easy recogni-
tion by either humans or microprocessors. See Table 3.
CHRG requires a pull-up resistor and/or LED to provide
indication.
be connected from SW to V
.
OUT
FAULT (Pin 38): Open-Drain Status Output. Used to in-
dicate fault condition in any of the four general purpose
voltage regulators.
GND (Exposed Pad Pin 39): Ground. The exposed pad
should be connected to a continuous ground plane on the
second layer of the printed circuit board by several vias
directly under the LTC3586-2/LTC3586-3.
358623f
13
LTC3586-2/LTC3586-3
BLOCK DIAGRAM
35, 36
V
BUS
2.25MHz
PowerPath
SWITCHING
REGULATOR
SW
37
3
LDO3V3
3.3V LDO
SUSPEND
LDO
500µA
V
34
31
OUT
+
–
+
–
+
+
GATE
IDEAL
CC/CV
CLPROG
NTC
4
5
–
CHARGER
–
+
15mV
0.3V
–
+
BATTERY
TEMPERATURE
MONITOR
BAT
32
29
27
1.188V
3.6V
PROG
V
IN1
EN1
CHRG 30
FAULT 38
EN1 21
CHARGE
STATUS
26 SW1
400mA
2.25MHz
(BUCK)
SWITCHING
REGULATOR 1
FB1
28
24
FAULT
LOGIC
V
IN2
EN2
400mA
2.25MHz
EN2
EN3
20
18
33
9
25 SW2
(BUCK)
SWITCHING
REGULATOR 2
EN4
MASTER LOGIC
FB2
23
MODE
I
1
LIM0
14, 15
V
IN3
I
2
LIM1
EN3
A
13 SWAB3
V
22
IN4
B
1A
2.25MHz
(BUCK-BOOST)
SWITCHING
REGULATOR 3
6, 7
16, 17
V
V
OUT3
OUT4
EN4
800mA
2.25MHz
D
C
19 SWCD3
SW4
FB4
(BOOST)
8
SWITCHING
REGULATOR 4
FB3
11
12
10
V
C3
39
358623 BD
GND
358623f
14
LTC3586-2/LTC3586-3
OPERATION
Introduction
the voltage across the battery charger low, efficiency is
optimized because power lost to the linear battery char-
ger is minimized. Power available to the external load is
therefore optimized.
The LTC3586-2/LTC3586-3 are highly integrated power
management ICs which include a high efficiency switch
mode PowerPath controller, a battery charger, an ideal
diode, an always-on LDO, two 400mA buck switching
regulators, a 1A buck-boost switching regulator, and an
800mA boost switching regulator. All of the regulators can
be independently controlled via ENABLE pins.
If the combined load at V
is large enough to cause the
OUT
switching PowerPath supply to reach the programmed
input current limit, the battery charger will reduce its
charge current by that amount necessary to enable the
external load to be satisfied. Even if the battery charge
currentissettoexceedtheallowableUSBcurrent,theUSB
specification will not be violated. The PowerPath switch-
ing regulator will limit the average input current so that
the USB specification is never violated. Furthermore, load
DesignedspecificallyforUSBapplications,thePowerPath
controller incorporates a precision average input current
buck switching regulator to make maximum use of the
allowable USB power. Because power is conserved, the
LTC3586-2/LTC3586-3 allow the load current on V
exceed the current drawn by the USB port without exceed-
ing the USB load specifications.
to
OUT
current at V
will always be prioritized and only excess
OUT
available power will be used to charge the battery.
If the voltage at BAT is below 3.3V, or the battery is not
present, and the load requirement does not cause the
PowerPath switching regulator to exceed the USB
The PowerPath switching regulator and battery charger
communicatetoensurethattheinputcurrentneverviolates
the USB specifications.
specification, V
will regulate at 3.6V, as shown in
OUT
The ideal diode from BAT to V
guarantees that ample
OUT
Figure 1. This “instant-on” feature will allow a portable
producttorunimmediatelywhenpowerisappliedwithout
waiting for the battery to charge. If the load exceeds the
powerisalwaysavailabletoV evenifthereisinsufficient
OUT
or absent power at V
.
BUS
current limit at V
V
will range between the no-load
BUS, OUT
An always-on LDO provides a regulated 3.3V from avail-
voltage and slightly below the battery voltage, indicated
by the shaded region of Figure 1.
able power at V . Drawing very little quiescent current,
OUT
this LDO will be on at all times and can be used to supply
up to 20mA.
For very low-battery voltages, the battery charger acts like
a load and, due to limited input power, its current will tend
Along with constant frequency PWM mode, the buck and
the buck-boost switching regulators have a low power
burst mode setting for significantly reduced quiescent
current under light load conditions.
topullV belowthe3.6V“instant-on”voltage.Toprevent
OUT
V
OUT
from falling below this level, an undervoltage circuit
automatically detects that V
is falling and reduces the
OUT
batterychargeasneeded.Thisreductionensuresthatload
current and output voltages are always priortized while
allowing as much battery charge current as possible. See
Over-Programming the Battery Charger in Applications
Information Section.
High Efficiency Switching PowerPath Controller
Whenever V
is available and the PowerPath switch-
BUS
ing regulator is enabled, power is delivered from V
to
BUS
V
OUT
via SW. V
drives the combination of the external
OUT
The power delivered from V
to V
is controlled by a
OUT
load (including switching regulators 1, 2, 3 and 4) and
the battery charger.
BUS
2.25MHzconstant-frequencybuckswitchingregulator. To
meet the USB maximum load specification, the switching
regulator includes a control loop which ensures that the
average input current is below the level programmed at
CLPROG.
If the combined load does not exceed the PowerPath
switchingregulator’sprogrammedinputcurrentlimit,V
OUT
will track 0.3V above the battery (Bat-Track). By keeping
358623f
15
LTC3586-2/LTC3586-3
OPERATION
The current at CLPROG is a fraction (h
–1
If the load current increases beyond the power allowed
from the switching regulator, additional power will be
pulled from the battery via the ideal diode. Furthermore,
) of the
CLPROG
V
current. When a programming resistor and an av-
BUS
eraging capacitor are connected from CLPROG to GND,
the voltage on CLPROG represents the average input
current of the PowerPath switching regulator. When the
input current approaches the programmed limit, CLPROG
if power to V
(USB or wall power) is removed, then
BUS
all of the application power will be provided by the bat-
tery via the ideal diode. The transition from input power
to battery power at V
will be quick enough to allow
reaches V
, 1.188V and power out is held constant.
OUT
CLPROG
only the10µF capacitor to keep V
from drooping. The
The input current limit is programmed by the I
and
OUT
LIM0
ideal diode consists of a precision amplifier that enables
a large on-chip P-channel MOSFET transistor whenever
I
pins to limit average input current to one of several
LIM1
possiblesettingsaswellasbedeactivated(USBSuspend).
The input current limit will be set by the V servo
voltage and the resistor on CLPROG according to the fol-
lowing expression:
the voltage at V
is approximately 15mV (V ) below
OUT
FWD
CLPROG
the voltage at BAT. The resistance of the internal ideal
diode is approximately 180mΩ. If this is sufficient for the
application, then no external components are necessary.
However, if more conductance is needed, an external
P-channel MOSFET transistor can be added from BAT to
VCLPROG
RCLPROG
IVBUS = IVBUSQ
+
• h
(
+ 1
)
CLPROG
V . See Figure 2.
OUT
Figure 1 shows the range of possible voltages at V
a function of battery voltage.
as
OUT
When an external P-channel MOSFET transistor is pres-
ent, the GATE pin of the LTC3586-2/LTC3586-3 drive its
gate for automatic ideal diode control. The source of the
Ideal Diode from BAT to V
OUT
external P-channel MOSFET should be connected to V
OUT
The LTC3586-2/LTC3586-3 have an internal ideal diode as
well as a controller for an optional external ideal diode.
The ideal diode controller is always on and will respond
and the drain should be connected to BAT. Capable of
driving a 1nF load, the GATE pin can control an external
P-channel MOSFET transistor having an on-resistance of
40mΩ or lower.
quickly whenever V
drops below BAT.
OUT
4.5
4.2
3.9
2200
VISHAY Si2333
2000
OPTIONAL EXTERNAL
1800
1600
1400
1200
1000
800
IDEAL DIODE
LTC3586-2/
LTC3586-3
IDEAL DIODE
NO LOAD
3.6
3.3
3.0
2.7
2.4
300mV
600
ON
SEMICONDUCTOR
MBRM120LT3
400
200
0
3.6
4.2
240
300
360
420 480
2.4
2.7
3.0
3.3
3.9
0
120 180
60
FORWARD VOLTAGE (mV) (BAT – V
)
BAT (V)
OUT
358623 F01
358623 F02
Figure 1. VOUT vs BAT
Figure 2. Ideal Diode Operation
358623f
16
LTC3586-2/LTC3586-3
OPERATION
Suspend LDO
V
Undervoltage Lockout (UVLO)
BUS
If the LTC3586-2/LTC3586-3 are configured for USB sus-
pend mode, the switching regulator is disabled and the
AninternalundervoltagelockoutcircuitmonitorsV
and
BUS
BUS
keeps the PowerPath switching regulator off until V
suspend LDO provides power to the V
pin (presuming
rises above 4.30V and is about 200mV above the battery
voltage. Hysteresis on the UVLO turns off the regulator if
OUT
thereispoweravailabletoV ). ThisLDOwillpreventthe
BUS
battery from running down when the portable product has
access to a suspended USB port. Regulating at 4.6V, this
LDO only becomes active when the switching converter
is disabled (Suspended). To remain compliant with the
USB specification, the input to the LDO is current limited
so that it will not exceed the 500µA low power suspend
V
drops below 4.00V or to within 50mV of BAT. When
BUS
this happens, system power at V
the battery via the ideal diode.
will be drawn from
OUT
Battery Charger
The LTC3586-2/LTC3586-3 include a constant-current/
constant-voltagebatterychargerwithautomaticrecharge,
automatic termination by safety timer, low voltage trickle
charging, bad cell detection and thermistor sensor input
for out-of-temperature charge pausing.
specification. If the load on V
exceeds the suspend
OUT
current limit, the additional current will come from the
battery via the ideal diode.
3.3V Always-On Supply
Battery Preconditioning
TheLTC3586-2/LTC3586-3includealowquiescentcurrent
low dropout regulator that is always powered. This LDO
can be used to provide power to a system pushbutton
controller, standby microcontroller or real-time clock. De-
signed to deliver up to 20mA, the always-on LDO requires
at least a 1µF low impedance ceramic bypass capacitor
When a battery charge cycle begins, the battery charger
first determines if the battery is deeply discharged. If the
batteryvoltageisbelowV
,typically2.85V,anautomatic
TRKL
trickle charge feature sets the battery charge current to
10% of the programmed value. If the low voltage persists
for more than 1/2 hour, the battery charger automatically
terminates and indicates via the CHRG pin that the battery
was unresponsive.
for compensation. The LDO is powered from V , and
OUT
therefore will enter dropout at loads less than 20mA as
V
falls near 3.3V. If the LDO3V3 output is not used, it
OUT
should be disabled by connecting it to V
.
OUT
3.5V TO
TO USB
OR WALL
ADAPTER
V
BUS
SW
OUT
(BAT + 0.3V)
TO SYSTEM
LOAD
37
34
35, 36
V
PWM AND
GATE DRIVE
IDEAL
DIODE
I
/
SWITCH
OPTIONAL
h
CLPROG
+
–
GATE
BAT
EXTERNAL
IDEAL DIODE
PMOS
CONSTANT-CURRENT
CONSTANT-VOLTAGE
BATTERY CHARGER
31
32
–
+
15mV
–
+
–
+
+
0.3V
CLPROG
1.188V
4
+
–
3.6V
AVERAGE INPUT
CURRENT LIMIT
CONTROLLER
AVERAGE OUTPUT
VOLTAGE LIMIT
CONTROLLER
+
SINGLE CELL
Li-Ion
358623 F03
Figure 3. PowerPath Block Diagram
358623f
17
LTC3586-2/LTC3586-3
OPERATION
Oncethebatteryvoltageisabove2.85V,thebatterycharger
begins charging in full power constant-current mode. The
current delivered to the battery will try to reach 1022V/
Charge Current
The charge current is programmed using a single resis-
tor from PROG to ground. 1/1022th of the battery charge
current is sent to PROG which will attempt to servo to
1.000V. Thus, the battery charge current will try to reach
1022 times the current in the PROG pin. The program
resistor and the charge current are calculated using the
following equations:
R
. Depending on available input power and external
PROG
load conditions, the battery charger may or may not be
able to charge at the full programmed rate. The external
load will always be prioritized over the battery charge
current. The USB current limit programming will always
be observed and only additional power will be available to
charge the battery. When system loads are light, battery
charge current will be maximized.
1022V
ICHG
1022V
RPROG
RPROG
=
, ICHG =
Ineithertheconstant-currentorconstant-voltagecharging
modes, the voltage at the PROG pin will be proportional to
the actual charge current delivered to the battery. There-
fore, the actual charge current can be determined at any
time by monitoring the PROG pin voltage and using the
following equation:
Charge Termination
The battery charger has a built-in safety timer. When the
voltage on the battery reaches the pre-programmed float
voltage, the battery charger will regulate the battery volt-
age and the charge current will decrease naturally. Once
the battery charger detects that the battery has reached
the float voltage, the four hour safety timer is started.
After the safety timer expires, charging of the battery will
discontinue and no more current will be delivered.
VPROG
RPROG
IBAT
=
•1022
In many cases, the actual battery charge current, I , will
BAT
Automatic Recharge
belowerthanI
duetolimitedinputpoweravailableand
CHG
prioritization with the system load drawn from V
.
OUT
After the battery charger terminates, it will remain off
drawing only microamperes of current from the battery.
If the portable product remains in this state long enough,
the battery will eventually self discharge. To ensure that
the battery is always topped off, a charge cycle will auto-
matically begin when the battery voltage falls below the
recharge threshold which is typically 100mV less than
the charger’s float voltage. In the event that the safety
timer is running when the battery voltage falls below the
recharge threshold, it will reset back to zero. To prevent
brief excursions below the recharge threshold from reset-
ting the safety timer, the battery voltage must be below
the recharge threshold for more than 1.3ms. The charge
Charge Status Indication
The CHRG pin indicates the status of the battery charger.
Four possible states are represented by CHRG which in-
clude charging, not charging, unresponsive battery, and
battery temperature out of range.
The signal at the CHRG pin can be easily recognized as
one of the above four states by either a human or a mi-
croprocessor. An open-drain output, the CHRG pin can
drive an indicator LED through a current limiting resistor
for human interfacing or simply a pull-up resistor for
microprocessor interfacing.
cycle and safety timer will also restart if the V
cycles low and then high (e.g., V
replaced).
UVLO
BUS
is removed and then
BUS
358623f
18
LTC3586-2/LTC3586-3
OPERATION
Note that the LTC3586-2/LTC3586-3 are 3-terminal
PowerPath products where system load is always pri-
oritized over battery charging. Due to excessive system
load, there may not be sufficient power to charge the
battery beyond the trickle charge threshold voltage
within the bad battery timeout period. In this case, the
battery charger will falsely indicate a bad battery. System
software may then reduce the load and reset the battery
charger to try again.
To make the CHRG pin easily recognized by both humans
and microprocessors, the pin is either LOW for charging,
HIGH for not charging, or it is switched at high frequency
(35kHz) to indicate the two possible faults, unresponsive
battery and battery temperature out of range.
When charging begins, CHRG is pulled low and remains
low for the duration of a normal charge cycle. When
charging is complete, i.e., the BAT pin reaches the float
voltage and the charge current has dropped to one tenth
oftheprogrammedvalue, theCHRGpinisreleased(Hi-Z).
If a fault occurs, the pin is switched at 35kHz. While
switching, its duty cycle is modulated between a high
and low value at a very low frequency. The low and high
duty cycles are disparate enough to make an LED appear
to be on or off thus giving the appearance of “blinking”.
Each of the two faults has its own unique “blink” rate for
human recognition as well as two unique duty cycles for
machine recognition.
Although very improbable, it is possible that a duty cycle
reading could be taken at the bright-dim transition (low
duty cycle to high duty cycle). When this happens the
duty cycle reading will be precisely 50%. If the duty cycle
reading is 50%, system software should disqualify it and
take a new duty cycle reading.
NTC Thermistor
The battery temperature is measured by placing a nega-
tive temperature coefficient (NTC) thermistor close to the
battery pack.
The CHRG pin does not respond to the C/10 threshold if
the LTC3586-2/LTC3586-3 are in V
current limit. This
BUS
preventsfalseend-of-chargeindicationsduetoinsufficient
To use this feature, connect the NTC thermistor, R
,
,
NTC
power available to the battery charger.
between the NTC pin and ground and a resistor, R
NOM
from V
to the NTC pin. R
should be a 1% resis-
BUS
NOM
Table 3 illustrates the four possible states of the CHRG
pin when the battery charger is active.
tor with a value equal to the value of the chosen NTC
thermistor at 25°C (R25). A 100k thermistor is recom-
mended since thermistor current is not measured by the
LTC3586-2/LTC3586-3 and will have to be budgeted for
USB compliance.
Table 3. CHRG Signal
MODULATION
STATUS
FREQUENCY (BLINK) FREQUENCY
DUTY CYCLES
100%
Charging
0Hz
0Hz
35kHz
35kHz
0Hz (Lo-Z)
0Hz (Hi-Z)
1.5Hz at 50%
6.1Hz at 50%
Not Charging
NTC Fault
Bad Battery
0%
The LTC3586-2/LTC3586-3 will pause charging when the
resistance of the NTC thermistor drops to 0.54 times the
value of R25 or approximately 54k. For Vishay “Curve 1”
thermistor, this corresponds to approximately 40°C. If the
battery charger is in constant voltage (float) mode, the
safety timer also pauses until the thermistor indicates a
return to a valid temperature. As the temperature drops,
theresistanceoftheNTCthermistorrises.TheLTC3586-2/
LTC3586-3 are also designed to pause charging when the
value of the NTC thermistor increases to 3.25 times the
value of R25. For Vishay “Curve 1” this resistance, 325k,
corresponds to approximately 0°C. The hot and cold
comparators each have approximately 3°C of hysteresis
to prevent oscillation about the trip point. Grounding the
NTC pin disables the NTC charge pausing function.
358623f
6.25% to 93.75%
12.5% to 87.5%
An NTC fault is represented by a 35kHz pulse train whose
duty cycle varies between 6.25% and 93.75% at a 1.5Hz
rate. A human will easily recognize the 1.5Hz rate as a
“slow” blinking which indicates the out-of-range battery
temperaturewhileamicroprocessorwillbeabletodecode
either the 6.25% or 93.75% duty cycles as an NTC fault.
If a battery is found to be unresponsive to charging (i.e.,
its voltage remains below 2.85V for 1/2 hour), the CHRG
pingivesthebatteryfaultindication.Forthisfault,ahuman
would easily recognize the frantic 6.1Hz “fast” blink of the
LEDwhileamicroprocessorwouldbeabletodecodeeither
the 12.5% or 87.5% duty cycles as a bad battery fault.
19
LTC3586-2/LTC3586-3
OPERATION
Thermal Regulation
output voltage of 0.8V and can be used to power a micro-
controllercore, microcontrollerI/O, memory, diskdriveor
other logic circuitry. Both buck converters support 100%
duty cycle operation (low dropout mode) when their input
voltage drops very close to their output voltage. To suit a
variety of applications, selectable mode functions can be
used to trade-off noise for efficiency. Two modes are avail-
abletocontroltheoperationoftheLTC3586-2/LTC3586-3’s
buck regulators. At moderate to heavy loads, the pulse-
skippingmodeprovidestheleastnoiseswitchingsolution.
At lighter loads, Burst Mode operation may be selected.
The buck regulators include soft-start to limit inrush cur-
rent when powering on, short-circuit current protection
and switch node slew limiting circuitry to reduce radiated
EMI. Noexternalcompensationcomponentsarerequired.
The operating mode of the buck regulators can be set by
the MODE pin. The buck converters can be individually
enabled by the EN1 and EN2 pins. Both buck regulators
have a fixed feedback servo voltage of 800mV. The buck
To optimize charging time, an internal thermal feedback
loop may automatically decrease the programmed charge
current. This will occur if the die temperature rises to
approximately 110°C. Thermal regulation protects the
LTC3586-2/LTC3586-3fromexcessivetemperaturedueto
high power operation or high ambient thermal conditions
and allows the user to push the limits of the power han-
dling capability with a given circuit board design without
risk of damaging the LTC3586-2/LTC3586-3 or external
components. The benefit of the LTC3586-2/LTC3586-3
thermal regulation loop is that charge current can be set
according to actual conditions rather than worst-case
conditions with the assurance that the battery charger will
automaticallyreducethecurrentinworst-caseconditions.
A flow chart of battery charger operation can be seen in
Figure 4.
Low Supply Operation
regulator input supplies V and V will generally be
IN1
IN2
connected to the system load pin V
.
The LTC3586-2/LTC3586-3 incorporate an undervoltage
OUT
lockout circuit on V
which shuts down all four general
OUT
Buck Regulator Output Voltage Programming
purpose switching regulators when V
drops below
OUT
V . This UVLO prevents unstable operation.
OUTUVLO
Both buck regulators can be programmed for output volt-
ages greater than 0.8V. The output voltage for each buck
regulator is programmed using a resistor divider from the
buckregulatoroutputconnectedtothefeedbackpins(FB1
and FB2) such that:
FAULT Pin
FAULT is an open-drain output used to indicate a fault
condition on any of the general purpose regulators. If
the FB pin voltage of any of the enabled regulators stays
below 92% of the internal reference voltage (0.8V) for
more than 14ms, a fault condition will be reported by
FAULT going low. Since FAULT is an open-drain output,
it requires a pull-up resistor to the input voltage of the
monitoring microprocessor or another appropriate power
source such as LD03V3.
R1
R2
V
= V
+ 1
FBX
OUTX
where V is fixed at 0.8V and X = 1, 2. See Figure 5.
FB
Typical values for R1 are in the range of 40k to 1M. The
capacitorC cancelsthepolecreatedbyfeedbackresistors
FB
and the input capacitance of the FBx pin and also helps
to improve transient response for output voltages much
greater than 0.8V. A variety of capacitor sizes can be used
General Purpose Buck Switching Regulators
TheLTC3586-2/LTC3586-3containtwo2.25MHzconstant-
frequency current mode buck switching regulators. Each
buckregulatorcanprovideupto400mAofoutputcurrent.
Both buck regulators can be programmed for a minimum
for C but a value of 10pF is recommended for most ap-
FB
plications. Experimentation with capacitor sizes between
2pF and 22pF may yield improved transient response.
358623f
20
LTC3586-2/LTC3586-3
OPERATION
POWER ON
CLEAR EVENT TIMER
ASSERT CHRG LOW
YES
INHIBIT CHARGER
NTC OUT OF RANGE
NO
BAT < 2.85V
BAT > 4.15V
YES
CHRG CURRENTLY
BATTERY STATE
HIGH-Z
2.85V < BAT < 4.15V
CHARGE AT
NO
CHARGE WITH
FIXED VOLTAGE
(4.200V)
INDICATE
NTC FAULT
AT CHRG
CHARGE AT
PROG
100V/R
(C/10 RATE)
1022V/R
RATE
PROG
RUN EVENT TIMER
PAUSE EVENT TIMER
RUN EVENT TIMER
TIMER > 4 HOURS
NO
NO
TIMER > 30 MINUTES
YES
YES
NO
INHIBIT CHARGING
STOP CHARGING
I
< C/10
YES
BAT
YES
YES
INDICATE BATTERY
BAT RISING
RELEASE CHRG
RELEASE CHRG
FAULT AT CHRG
THROUGH 4.1V
HIGH-Z
HIGH-Z
NO
NO
NO
BAT FALLING
THROUGH 4.1V
BAT > 2.85V
YES
BAT < 4.1V
YES
NO
358623 F04
Figure 4. Flow Chart for Battery Charger Operation (LTC3586-2)
358623f
21
LTC3586-2/LTC3586-3
OPERATION
In Burst Mode operation, the buck regulator automati-
cally switches between fixed frequency PWM operation
and hysteretic control as a function of the load current.
At light loads, the buck regulators operate in hysteretic
mode in which the output capacitor is charged to a volt-
age slightly higher than the regulation point. The buck
converter then goes into sleep mode, during which the
output capacitor provides the load current. In sleep mode,
most of the regulator’s circuitry is powered down, helping
conserve battery power. When the output voltage drops
below a predetermined value, the buck regulator circuitry
is powered on and the normal PWM operation resumes.
The duration for which the buck regulator operates in
sleep mode depends on the load current. The sleep time
decreases as the load current increases. Beyond a certain
load current point (about 1/4 rated output load current)
the step-down switching regulators will switch to a low
noise constant frequency PWM mode of operation, much
the same as pulse-skipping operation at high loads. For
applications that can tolerate some output ripple at low
output currents, Burst Mode operation provides better
efficiency than pulse skip at light loads while still provid-
ing the full specified output current of the buck regulator.
V
INx
L
V
SWx
OUTx
LTC3586-2/
LTC3586-3
C
R1
C
OUT
FB
FBx
X = 1, 2
R2
GND
358623 F05
Figure 5. Buck Converter Application Circuit
Buck Regulator Operating Modes
The LTC3586-2/LTC3586-3’s buck regulators include two
possible operating modes to meet the noise/ power needs
of a variety of applications.
In pulse-skipping mode, an internal latch is set at the
start of every cycle which turns on the main P-channel
MOSFET switch. During each cycle, a current compara-
tor compares the peak inductor current to the output of
an error amplifier. The output of the current comparator
resets the internal latch which causes the main P-channel
MOSFET switch to turn off and the N-channel MOSFET
synchronous rectifier to turn on. The N-channel MOSFET
synchronous rectifier turns off at the end of the 2.25MHz
cycle or if the current through the N-channel MOSFET
synchronous rectifier drops to zero. Using this method
of operation, the error amplifier adjusts the peak inductor
current to deliver the required output power. All neces-
sary compensation is internal to the switching regulator
requiring only a single ceramic output capacitor for sta-
bility. At light loads, the inductor current may reach zero
on each pulse which will turn off the N-channel MOSFET
synchronous rectifier. In this case, the switch node (SW1,
SW2) goes high impedance and the switch node voltage
will “ring”. This is discontinuous mode operation, and is
normal behavior for a switching regulator. At very light
loads, the buck regulators will automatically skip pulses
as needed to maintain output regulation.
The buck regulators allow mode transition on the fly,
providing seamless transition between modes even under
load.Thisallowstheusertoswitchbackandforthbetween
modes to reduce output ripple or increase low current
efficiency as needed.
Buck Regulator in Shutdown
The buck regulators are in shutdown when not enabled for
operation. In shutdown, all circuitry in the buck regulator
is disconnected from the buck regulator input supply
leaving only a few nanoamps of leakage current. The
buck regulator outputs are individually pulled to ground
through a 10k resistor on the switch pins (SW1 and SW2)
when in shutdown.
At high duty cycles (V
> V /2) it is possible for the
INx
OUTx
Buck Regulator Dropout Operation
inductor current to reverse, causing the buck regulator
to operate continuously at light loads. This is normal and
regulationismaintained,butthesupplycurrentwillincrease
to several milliamperes due to continuous switching.
It is possible for a buck regulator’s input voltage, V , to
INx
approach its programmed output voltage (e.g., a battery
voltageof3.4Vwithaprogrammedoutputvoltageof3.3V).
358623f
22
LTC3586-2/LTC3586-3
OPERATION
Whenthishappens,thePMOSswitchdutycycleincreases
until it is turned on continuously at 100%. In this dropout
condition, the respective output voltage equals the buck
regulator’s input voltage minus the voltage drops across
the internal P-channel MOSFET and the inductor.
divided output voltage with a reference and adjusts the
compensation voltage accordingly until the FB3 pin has
stabilizedtothereferencevoltage(0.8V).Thebuck-boost
regulator includes a soft-start to limit inrush current and
voltage overshoot when powering on, short-circuit cur-
rent protection, and switch node slew limiting circuitry
for reduced radiated EMI.
Buck Regulator Soft-Start Operation
Soft-start is accomplished by gradually increasing the
peakinductorcurrentforeachbuckregulatorovera500µs
period. This allows each output to rise slowly, helping
minimize the battery in-rush current. A soft-start cycle
occurs whenever a given buck regulator is enabled, or
after a fault condition has occurred (thermal shutdown
or UVLO). A soft-start cycle is not triggered by changing
operating modes. This allows seamless output operation
when transitioning between modes.
Input Current Limit
The input current limit comparator will shut the input
PMOS switch off once current exceeds 2.5A (typical). The
2.5A input current limit also protects against a grounded
V
node.
OUT3
Output Overvoltage Protection
If the FB3 node were inadvertently shorted to ground, then
the output would increase indefinitely with the maximum
Buck Regulator Switching Slew Rate Control
current that could be sourced from V . The LTC3586-2/
IN3
The buck regulators contain new patent pending circuitry
to limit the slew rate of the switch node (SW1 and SW2).
Thisnewcircuitryisdesignedtotransitiontheswitchnode
over a period of a couple of nanoseconds, significantly
reducing radiated EMI and conducted supply noise.
LTC3586-3 protect against this by shutting off the input
PMOS if the output voltage exceeds 5.6V (typical).
Low Output Voltage Operation
When the output voltage is below 2.65V (typical) during
start-up, Burst Mode operation is disabled and switch D
is turned off (allowing forward current through the well
diode and limiting reverse current to 0mA).
BUCK-BOOST DC/DC SWITCHING REGULATOR
The LTC3586-2/LTC3586-3 contain a 2.25MHz constant-
frequencyvoltage-modebuck-boostswitchingregulator.
The regulator provides up to 1A of output load current.
Thebuck-boostcanbeprogrammedtoaminimumoutput
voltage of 2.5V and can be used to power a microcon-
troller core, microcontroller I/O, memory, disk drive, or
other logic circuitry. The converter is enabled by pulling
EN3 high. To suit a variety of applications, a selectable
mode function allows the user to trade-off noise for ef-
ficiency. Twomodesareavailabletocontroltheoperation
of the LTC3586-2/LTC3586-3’s buck-boost regulator. At
moderate to heavy loads, the constant frequency PWM
mode provides the least noise switching solution. At
lighter loads Burst Mode operation may be selected. The
outputvoltageisprogrammedbyauser-suppliedresistive
divider returned to FB3. An error amplifier compares the
Buck-Boost Regulator PWM Operating Mode
In PWM mode the voltage seen at FB3 is compared to the
reference voltage (0.8V). From the FB3 voltage an error
amplifier generates an error signal seen at V . This error
C3
signalcommandsPWMwaveformsthatmodulateswitches
A, B, C, and D. Switches A and B operate synchronously
as do switches C and D. If V is significantly greater
IN3
than the programmed V
, then the converter will op-
OUT3
erate in buck mode. In this case switches A and B will be
modulated, with switch D always on (and switch C always
off), to step-down the input voltage to the programmed
output. If V is significantly less than the programmed
IN3
V
, then the converter will operate in boost mode. In
this case switches C and D are modulated, with switch A
OUT3
358623f
23
LTC3586-2/LTC3586-3
OPERATION
always on (and switch B always off), to step-up the input
Buck-Boost Regulator Soft-Start Operation
voltage to the programmed output. If V is close to the
IN3
Soft-start is accomplished by gradually increasing the
programmed V
, then the converter will operate in
OUT3
maximum V voltage over a 0.5ms (typical) period.
C3
4-switchmode.Inthiscasetheswitchessequencethrough
the pattern of AD, AC, BD to either step the input voltage
up or down to the programmed output.
Ramping the V voltage limits the duty cycle and thus
C3
the V
voltage minimizing output overshoot during
OUT3
startup.Asoft-startcycleoccurswheneverthebuck-boost
is enabled, or after a fault condition has occurred (thermal
shutdown or UVLO). A soft-start cycle is not triggered by
changing operating modes. This allows seamless output
operation when transitioning between Burst Mode opera-
tion and PWM mode.
Buck-Boost Regulator Burst-Mode Operation
In Burst Mode operation, the buck-boost regulator uses
a hysteretic FB3 voltage algorithm to control the output
voltage. By limiting FET switching and using a hysteretic
control loop, switching losses are greatly reduced. In this
mode output current is limited to 50mA typical. While
operating in Burst Mode operation, the output capacitor
is charged to a voltage slightly higher than the regulation
point. The buck-boost converter then goes into a sleep
state, during which the output capacitor provides the load
current. The output capacitor is charged by charging the
inductor until the input current reaches 250mA typical
andthendischargingtheinductoruntilthereversecurrent
reaches 0mA typical. This process is repeated until the
feedbackvoltagehaschargedto6mVabovetheregulation
point. In the sleep state, most of the regulator’s circuitry
is powered down, helping to conserve battery power.
When the feedback voltage drops 6mV below the regula-
tion point, the switching regulator circuitry is powered on
and another burst cycle begins. The duration for which
the regulator sleeps depends on the load current and
output capacitor value. The sleep time decreases as the
load current increases. The buck-boost regulator will not
go to sleep if the current is greater than 50mA, and if the
load current increases beyond this point while in Burst
Mode operation the output will lose regulation. Burst
Mode operation provides a significant improvement in
efficiencyatlightloadsattheexpenseofhigheroutputripple
when compared to PWM mode. For many noise-sensitive
systems, Burst Mode operation might be undesirable at
certain times (i.e., during a transmit or receive cycle of a
wireless device), but highly desirable at others (i.e., when
the device is in low power standby mode). The MODE pin
is used to enable or disable Burst Mode operation at any
time, offering both low noise and low power operation
when they are needed.
SYNCHRONOUS BOOST DC/DC SWITCHING
REGULATOR
The LTC3586-2/LTC3586-3 contain a 2.25MHz constant-
frequency current mode synchronous boost switching
regulatorwithtrueoutputdisconnectfeature.Theregulator
provides at least 800mA of output load current and the
output voltage can be programmed up to a maximum of
5V. The converter is enabled by pulling EN4 high. The
boost regulator also includes soft-start to limit inrush
current and voltage overshoot when powering on, short
circuit current protection and switch node slew limiting
circuitry for reduced radiated EMI.
Error Amp
The boost output voltage is programmed by a user-sup-
pliedresistivedividerreturnedtotheFB4pin. Aninternally
compensated error amplifier compares the divided output
voltage with an internal 0.8V reference and adjusts the
voltage accordingly until FB4 servos to 0.8V.
Current Limit
Lossless current sensing converts the NMOS switch cur-
rent signal to a voltage to be summed with the internal
slope compensation signal. The summed signal is then
compared to the error amplifier output to provide a peak
current control command for the peak comparator. Peak
switch current is limited to 2.8A independent of output
voltage.
358623f
24
LTC3586-2/LTC3586-3
OPERATION
Zero Current Comparator
internalfeaturessuchascurrentlimitfoldbackandthermal
shutdown for protection from an excessive overload or
short circuit.
Thezerocurrentcomparatormonitorstheinductorcurrent
to the output and shuts off the synchronous rectifier once
the current drops to approximately 65mA. This prevents
the inductor current from reversing in polarity thereby
improving efficiency at light loads.
V > V
Operation
IN
OUT
The LTC3586-2/LTC3586-3 boost converter will maintain
voltage regulation even if the input voltage is above
the output voltage. This is achieved by terminating the
Antiringing Control
switching of the synchronous PMOS and applying V
IN4
The antiringing control circuitry prevents high frequency
ringing of the SW pin as the inductor current goes to zero
in discontinuous mode. The damping of the resonant
statically on its gate. This ensures that the slope of the
inductor current will reverse during the time when cur-
rent is flowing to the output. Since the PMOS no longer
acts as a low impedance switch in this mode, there will
be more power dissipation within the IC. This will cause
a sharp drop in the efficiency (see Typical Performance
circuit formed by L and C (capacitance of the SW4
SW
pin) is achieved internally by switching a 150Ω resistor
across the inductor.
Characteristics, Boost Efficiency vs V ). The maximum
IN4
PMOS Synchronous Rectifier
output current should be limited in order to maintain an
To prevent the inductor current from running away,
the PMOS synchronous rectifier is only enabled when
acceptable junction temperature.
V
OUT
> (V + 130mV).
Boost Soft-Start
IN
TheLTC3586-2/LTC3586-3boostconverterprovidessoft-
start by slowly ramping the peak inductor current from
zero to a maximum of 2.8A in about 500µs. Ramping the
peak inductor current limits transient inrush currents
during start-up. A soft-start cycle occurs whenever the
boost is enabled, or after a fault condition has occurred
(thermal shutdown or UVLO).
Output Disconnect and Inrush Limiting
The LTC3586-2/LTC3586-3 boost converter is designed to
allow true output disconnect by eliminating body diode
conductionoftheinternalPMOSrectifier.ThisallowsV
OUT
to go to zero volts during shutdown, drawing zero current
from the input source. It also allows for inrush current
limiting at start-up, minimizing surge currents seen by the
input supply. Note that to obtain the advantage of output
disconnect, there must not be an external Schottky diode
Boost Overvoltage Protection
If the FB4 node were inadvertently shorted to ground, then
theboostconverteroutputwouldincreaseindefinitelywith
connected between the SW4 and V
pin.
OUT4
themaximumcurrentthatcouldbesourcedfromV .The
IN4
Short-Circuit Protection
LTC3586-2/LTC3586-3 protects against this by shutting
Unlike most boost converters, the LTC3586-2/LTC3586-3
boost converter allows its output to be short-circuited
due to the output disconnect feature. It incorporates
off the main switch if the output voltage exceeds 5.5V.
358623f
25
LTC3586-2/LTC3586-3
APPLICATIONS INFORMATION
PowerPath CONTROLLER APPLICATIONS SECTION
V
and V
Bypass Capacitors
OUT
BUS
ThestyleandvalueofcapacitorsusedwiththeLTC3586-2/
LTC3586-3 determine several important parameters
such as regulator control-loop stability and input voltage
ripple. Because the LTC3586-2/LTC3586-3 use a buck
CLPROG Resistor and Capacitor
As described in the High Efficiency Switching PowerPath
Controller section, the resistor on the CLPROG pin deter-
mines the average input current limit when the switching
regulator is set to either the 1x mode (USB 100mA), the
5x mode (USB 500mA) or the 10x mode. The input cur-
rent will be comprised of two components, the current
switching power supply from V
to V , its input
BUS
OUT
current waveform contains high frequency components.
It is strongly recommended that a low equivalent series
resistance (ESR) multilayer ceramic capacitor be used to
that is used to drive V
and the quiescent current of the
bypass V . Tantalum and aluminum capacitors are not
OUT
BUS
switchingregulator.ToensurethattheUSBspecificationis
strictly met, both components of input current should be
considered. The Electrical Characteristics table gives the
worst-case values for quiescent currents in either setting
as well as current limit programming accuracy. To get as
close to the 500mA or 100mA specifications as possible,
recommended because of their high ESR. The value of the
capacitor on V
directly controls the amount of input
BUS
ripple for a given load current. Increasing the size of this
capacitor will reduce the input ripple.
To prevent large V
voltage steps during transient load
OUT
conditions, it is also recommended that a ceramic capaci-
a 1% resistor should be used. Recall that I
= I
VBUS
VBUSQ
tor be used to bypass V . The output capacitor is used
OUT
+ V
/R
• (h
+1).
CLPROG CLPPROG
CLPROG
in the compensation of the switching regulator. At least
An averaging capacitor is required in parallel with the
CLPROG resistor so that the switching regulator can
determine the average input current. This network also
provides the dominant pole for the feedback loop when
current limit is reached. To ensure stability, the capacitor
on CLPROG should be 0.1µF.
4µF of actual capacitance with low ESR are required on
V
. Additional capacitance will improve load transient
OUT
performance and stability.
Multilayer ceramic chip capacitors typically have excep-
tional ESR performance. MLCCs combined with a tight
board layout and an unbroken ground plane will yield very
good performance and low EMI emissions.
Choosing the PowerPath Inductor
Because the input voltage range and output voltage range
of the power path switching regulator are both fairly nar-
row, the LTC3586-2/LTC3586-3 are designed for a specific
inductance value of 3.3µH. Some inductors which may be
suitable for this application are listed in Table 4.
There are several types of ceramic capacitors available
each having considerably different characteristics. For
example,X7Rceramiccapacitorshavethebestvoltageand
temperature stability. X5R ceramic capacitors have appar-
ently higher packing density but poorer performance over
their rated voltage and temperature ranges. Y5V ceramic
capacitors have the highest packing density, but must be
used with caution, because of their extreme non-linear
characteristic of capacitance verse voltage. The actual
in-circuit capacitance of a ceramic capacitor should be
measured with a small AC signal as is expected in-circuit.
Many vendors specify the capacitance verse voltage with
a 1V RMS AC test signal and as a result overstate the ca-
pacitance that the capacitor will present in the application.
Using similar operating conditions as the application, the
user must measure or request from the vendor the actual
capacitance to determine if the selected capacitor meets
Table 4. Recommended Inductors for PowerPath Controller
MAX MAX
INDUCTOR
TYPE
L
I
DCR
(Ω)
SIZE IN mm
(L × W × H) MANUFACTURER
DC
(µH) (A)
LPS4018
3.3 2.2
0.08
Coilcraft
www.coilcraft.com
3.9 × 3.9 × 1.7
D53LC
DB318C
3.3 2.26 0.034
3.3 1.55 0.070
Toko
www.toko.com
5 × 5 × 3
3.8 × 3.8 × 1.8
WE-TPC
Type M1
3.3 1.95 0.065
Wurth Elektronik
www.we-online.com
4.8 × 4.8 × 1.8
CDRH6D12 3.3 2.2 0.0625
CDRH6D38 3.3 3.5 0.020
Sumida
www.sumida.com
6.7 × 6.7 × 1.5
7 × 7 × 4
the minimum capacitance that the application requires.
358623f
26
LTC3586-2/LTC3586-3
APPLICATIONS INFORMATION
TheVishay-DalethermistorNTHS0603N011-N1003F,used
in the following examples, has a nominal value of 100k
and follows the Vishay “Curve 1” resistance-temperature
characteristic.
Over-Programming the Battery Charger
The USB high power specification allows for up to 2.5W to
bedrawnfromtheUSBport(5V•500mA). ThePowerPath
switching regulator transforms the voltage at V
to just
BUS
In the explanation below, the following notation is used.
R25 = Value of the Thermistor at 25°C
abovethevoltageatBATwithhighefficiency,whilelimiting
power to less than the amount programmed at CLPROG.
In some cases the battery charger may be programmed
(withthePROGpin)todeliverthemaximumsafecharging
current without regard to the USB specifications. If there
is insufficient current available to charge the battery at the
programmed rate, the PowerPath regulator will reduce
R
R
= Value of thermistor at the cold trip point
NTC|COLD
= Value of the thermistor at the hot trip point
NTC|HOT
r
= Ratio of R
to R25
COLD
NTC|COLD
r
= Ratio of R
to R25
HOT
NTC|COLD
charge current until the system load on V
is satisfied
OUT
and the V
current limit is satisfied. Programming the
R
= Primary thermistor bias resistor
BUS
NOM
(see Figure 6a)
battery charger for more current than is available will
not cause the average input current limit to be violated.
It will merely allow the battery charger to make use of
all available power to charge the battery as quickly as
possible, and with minimal power dissipation within the
battery charger.
R1 = Optional temperature range adjustment resistor
(see Figure 6b)
ThetrippointsfortheLTC3586-2/LTC3586-3’stemperature
qualificationareinternallyprogrammedat0.349•V
for
BUS
the hot threshold and 0.765 • V
for the cold threshold.
BUS
Therefore, the hot trip point is set when:
Alternate NTC Thermistors and Biasing
RNTC|HOT
The LTC3586-2/LTC3586-3 provide temperature qualified
charging if a grounded thermistor and a bias resistor
are connected to NTC. By using a bias resistor whose
value is equal to the room temperature resistance of the
thermistor (R25) the upper and lower temperatures are
pre-programmed to approximately 40°C and 0°C, respec-
tively (assuming a Vishay “Curve 1” thermistor).
• VBUS = 0.349 • VBUS
RNOM + RNTC|HOT
and the cold trip point is set when:
RNTC|COLD
• VBUS = 0.765 • VBUS
RNOM + RNTC|COLD
The upper and lower temperature thresholds can be ad-
justed by either a modification of the bias resistor value
or by adding a second adjustment resistor to the circuit.
If only the bias resistor is adjusted, then either the upper
or the lower threshold can be modified but not both. The
other trip point will be determined by the characteristics
of the thermistor. Using the bias resistor in addition to an
adjustmentresistor,boththeupperandthelowertempera-
ture trip points can be independently programmed with
the constraint that the difference between the upper and
lower temperature thresholds cannot decrease. Examples
of each technique are given below.
SolvingtheseequationsforR
in the following:
andR
results
NTC|COLD
NTC|HOT
R
= 0.536 • R
NTC|HOT
NOM
and
R
= 3.25 • R
NTC|COLD
NOM
By setting R
equal to R25, the above equations result
NOM
= 0.536 and r
in r
= 3.25. Referencing these ratios
HOT
COLD
to the Vishay Resistance-Temperature Curve 1 chart gives
a hot trip point of about 40°C and a cold trip point of about
0°C. The difference between the hot and cold trip points
is approximately 40°C.
NTC thermistors have temperature characteristics which
areindicatedonresistance-temperatureconversiontables.
358623f
27
LTC3586-2/LTC3586-3
APPLICATIONS INFORMATION
By using a bias resistor, R
, different in value from
“temperature gain” of the thermistor as absolute tem-
perature increases.
NOM
R25, the hot and cold trip points can be moved in either
direction.Thetemperaturespanwillchangesomewhatdue
to the non-linear behavior of the thermistor. The following
equations can be used to easily calculate a new value for
the bias resistor:
The upper and lower temperature trip points can be inde-
pendentlyprogrammedbyusinganadditionalbiasresistor
asshowninFigure6b. Thefollowingformulascanbeused
to compute the values of R
and R1:
NOM
rHOT
0.536
rCOLD –rHOT
RNOM
RNOM
=
•R25
•R25
RNOM
=
•R25
2.714
rCOLD
3.25
R1= 0.536 •RNOM –rHOT •R25
=
For example, to set the trip points to 0°C and 45°C with
a Vishay Curve 1 thermistor choose:
where r
and r
are the resistance ratios at the de-
HOT
COLD
sired hot and cold trip points. Note that these equations
are linked. Therefore, only one of the two trip points can
be chosen, the other is determined by the default ratios
designed in the IC. Consider an example where a 60°C
hot trip point is desired.
3.266 – 0.4368
RNOM
=
•100k = 104.2k
2.714
the nearest 1% value is 105k:
R1 = 0.536 • 105k – 0.4368 • 100k = 12.6k
From the Vishay Curve 1 R-T characteristics, r
is
HOT
should
0.2488 at 60°C. Using the above equation, R
the nearest 1% value is 12.7k. The final circuit is shown
in Figure 6b and results in an upper trip point of 45°C and
a lower trip point of 0°C.
NOM
be set to 46.4k. With this value of R
, the cold trip point
NOM
is about 16°C. Notice that the span is now 44°C rather
than the previous 40°C. This is due to the decrease in
LTC3586-2/LTC3586-3
V
V
BUS
LTC3586-2/LTC3586-3
V
V
BUS
BUS
BUS
NTC BLOCK
NTC BLOCK
0.765 • V
0.765 • V
BUS
BUS
R
R
NOM
105k
NTC
NOM
–
+
–
+
100k
TOO_COLD
TOO_HOT
TOO_COLD
TOO_HOT
NTC
5
5
R
R1
12.7k
NTC
T
100k
–
+
–
+
0.349 • V
0.349 • V
BUS
BUS
R
NTC
T
100k
+
–
+
–
NTC_ENABLE
NTC_ENABLE
0.017 • V
0.017 • V
BUS
BUS
358623 F06a
358623 F06b
(6a)
(6b)
Figure 6. NTC Circuits
358623f
28
LTC3586-2/LTC3586-3
APPLICATIONS INFORMATION
USB Inrush Limiting
disconnected, a 4.7µF capacitor in series with a 0.2Ω to
1Ω resistor from BAT to GND is required to keep ripple
voltage low.
When a USB cable is plugged into a portable product,
the inductance of the cable and the high-Q ceramic input
capacitor form an L-C resonant circuit. If the cable does
not have adequate mutual coupling or if there is not much
impedance in the cable, it is possible for the voltage at
the input of the product to reach as high as twice the
USB voltage (~10V) before it settles out. In fact, due to
the high voltage coefficient of many ceramic capacitors, a
nonlinearity, the voltage may even exceed twice the USB
voltage. To prevent excessive voltage from damaging the
LTC3586-2/LTC3586-3 during a hot insertion, it is best to
High value, low ESR multilayer ceramic chip capacitors
reduce the constant-voltage loop phase margin, possibly
resulting in instability. Ceramic capacitors up to 22µF may
beusedinparallelwithabattery,butlargerceramicsshould
be decoupled with 0.2Ω to 1Ω of series resistance.
In constant-current mode, the PROG pin is in the feed-
back loop rather than the battery voltage. Because of the
additional pole created by any PROG pin capacitance,
capacitance on this pin must be kept to a minimum. With
no additional capacitance on the PROG pin, the battery
charger is stable with program resistor values as high
as 25k. However, additional capacitance on this node
reduces the maximum allowed program resistor. The pole
frequency at the PROG pin should be kept above 100kHz.
Therefore, if the PROG pin has a parasitic capacitance,
have a low voltage coefficient capacitor at the V
pin to
BUS
the LTC3586-2/LTC3586-3. This is achievable by selecting
an MLCC capacitor that has a higher voltage rating than
that required for the application. For example, a 16V, X5R,
10µF capacitor in a 1206 case would be a better choice
than a 6.3V, X5R, 10µF capacitor in a smaller 0805 case.
Alternatively, the soft connect circuit (Figure 7) can be
employed. In this circuit, capacitor C1 holds MP1 off
when the cable is first connected. Eventually C1 begins
to charge up to the USB input voltage applying increasing
gate support to MP1. The long time constant of R1 and
C1 prevent the current from building up in the cable too
fast thus dampening out any resonant overshoot.
C
, the following equation should be used to calculate
PROG
the maximum resistance value for R
:
PROG
1
RPROG
≤
2π •100kHz •CPROG
BUCK REGULATOR APPLICATIONS SECTION
Buck Regulator Inductor Selection
Battery Charger Stability Considerations
TheLTC3586-2/LTC3586-3’sbatterychargercontainsboth
a constant-voltage and a constant-current control loop.
The constant-voltage loop is stable without any compen-
sation when a battery is connected with low impedance
leads. Excessive lead length, however, may add enough
series inductance to require a bypass capacitor of at least
1µF from BAT to GND. Furthermore, when the battery is
Many different sizes and shapes of inductors are avail-
able from numerous manufacturers. Choosing the right
inductor from such a large selection of devices can be
overwhelming, but following a few basic guidelines will
make the selection process much simpler.
The buck converters are designed to work with inductors
in the range of 2.2µH to 10µH. For most applications a
4.7µH inductor is suggested for both buck regulators.
MP1
Si2333
V
BUS
Larger value inductors reduce ripple current which im-
proves output ripple voltage. Lower value inductors result
in higher ripple current and improved transient response
time. To maximize efficiency, choose an inductor with a
low DC resistance. For a 1.2V output, efficiency is reduced
about2%for100mΩseriesresistanceat400mAloadcur-
rent, andabout2%for300mΩseriesresistanceat100mA
358623f
C1
100nF
5V USB
INPUT
LTC3586-2/
LTC3586-3
C2
10µF
USB CABLE
R1
40k
GND
358623 F07
Figure 7. USB Soft Connect Circuit
29
LTC3586-2/LTC3586-3
APPLICATIONS INFORMATION
load current. Choose an inductor with a DC current rating
at least 1.5 times larger than the maximum load current to
ensure that the inductor does not saturate during normal
operation. If output short circuit is a possible condition,
the inductor should be rated to handle the maximum peak
current specified for the buck converters.
Buck Regulator Input/Output Capacitor Selection
Low ESR (equivalent series resistance) MLCC capacitors
shouldbeusedatbothbuckregulatoroutputsaswellasat
eachbuckregulatorinputsupply(V andV ).OnlyX5R
IN1
IN2
or X7R ceramic capacitors should be used because they
retaintheircapacitanceoverwidervoltageandtemperature
ranges than other ceramic types. A 10µF output capaci-
tor is sufficient for most applications. For good transient
response and stability the output capacitor should retain
at least 4µF of capacitance over operating temperature
and bias voltage. Each buck regulator input supply should
be bypassed with a 1µF capacitor. Consult with capacitor
manufacturers for detailed information on their selection
and specifications of ceramic capacitors. Many manufac-
turers now offer very thin (<1mm tall) ceramic capacitors
ideal for use in height-restricted designs. Table 6 shows a
list of several ceramic capacitor manufacturers.
Different core materials and shapes will change the size/
currentandprice/currentrelationshipofaninductor.Toroid
or shielded pot cores in ferrite or Permalloy materials are
small and don’t radiate much energy, but generally cost
more than powdered iron core inductors with similar
electrical characteristics. Inductors that are very thin or
have a very small volume typically have much higher core
and DCR losses, and will not give the best efficiency. The
choice of which style inductor to use often depends more
on the price vs size, performance and any radiated EMI
requirements than on what the LTC3586-2/LTC3586-3
require to operate.
Table 6. Recommended Ceramic Capacitor Manufacturers
The inductor value also has an effect on Burst Mode
operations. Lower inductor values will cause the Burst
Mode switching frequencies to increase.
AVX
www/avxcorp.com
www.murata.com
www.t-yuden.com
www.vishay.com
www.tdk.com
Murata
Taiyo Yuden
Vishay Siliconix
TDK
Table 5 shows several inductors that work well with the
LTC3586-2/LTC3586-3’sbuckregulators.Theseinductors
offeragoodcompromiseincurrentrating,DCRandphysi-
calsize.Consulteachmanufacturerfordetailedinformation
on their entire selection of inductors.
BUCK-BOOST REGULATOR APPLICATIONS SECTION
Buck-Boost Regulator Inductor Selection
Table 5. Recommended Inductors for Buck Regulators
MAX MAX
Inductor selection criteria for the buck-boost are similar
to those given for the buck switching regulator. The buck-
boost converter is designed to work with inductors in the
rangeof1µHto5µH.Formostapplicationsa2.2µHinductor
will suffice. Choose an inductor with a DC current rating
at least 2 times larger than the maximum load current to
ensure that the inductor does not saturate during normal
operation. If output short circuit is a possible condition,
the inductor should be rated to handle the maximum peak
current specified for the buck-boost converter.
INDUCTOR
TYPE
L
I
DCR
(Ω)
SIZE IN mm
DC
(µH) (A)
(L × W × H) MANUFACTURER
DE2818C
DE2812C
4.7 1.25 0.072*
4.7 1.15 0.13*
Toko
3.0 × 2.8 × 1.8
3.0 × 2.8 × 1.2
4 × 4 × 1.8
www.toko.com
CDRH3D16 4.7 0.9
0.11
Sumida
www.sumida.com
SD3118
SD3112
LPS3015
4.7 1.3 0.162
4.7 0.8 0.246
Cooper
3.1 × 3.1 × 1.8
3.1 × 3.1 × 1.2
3.0 × 3.0 × 1.5
www.cooperet.com
4.7 1.1
0.2
Coilcraft
www.coilcraft.com
Table 7 shows several inductors that work well with the
LTC3586-2/LTC3586-3’s buck-boost regulator. These in-
ductors offer a good compromise in current rating, DCR
and physical size. Consult each manufacturer for detailed
information on their entire selection of inductors.
*Typical DCR
358623f
30
LTC3586-2/LTC3586-3
APPLICATIONS INFORMATION
Table 7. Recommended Inductors for Buck-Boost Regulator
Closing the Feedback Loop
MAX MAX
DC
(µH) (A)
TheLTC3586-2/LTC3586-3incorporatevoltagemodePWM
control. The control to output gain varies with operation
region(buck, boost, buck-boost), butisusuallynogreater
than 20. The output filter exhibits a double pole response
given by:
INDUCTOR
TYPE
L
I
DCR
(Ω)
SIZE IN mm
(L × W × H) MANUFACTURER
LPS4018
3.3 2.2
2.2 2.5
0.08
0.07
Coilcraft
www.coilcraft.com
3.9 × 3.9 × 1.7
3.9 × 3.9 × 1.7
D53LC
2.0 3.25 0.02
Toko
www.toko.com
5.0 × 5.0 × 3.0
4.8 × 4.8 × 2.8
4.7 × 4.7 × 2.4
1
7440430022 2.2 2.5 0.028
Würth-Elektronik
www.we-online.com
fFILTER _POLE
=
Hz
2 • π • L •COUT
is the output filter capacitor.
CDRH4D22/ 2.2 2.4 0.044
HP
Sumida
www.sumida.com
where C
OUT
SD14
2.0 2.56 0.045
Cooper
www.cooperet.com
5.2 × 5.2 ×
The output filter zero is given by:
1.45
1
fFILTER _ ZERO
=
Hz
Buck-Boost Regulator Input/Output Capacitor
Selection
2 • π •RESR •COUT
where R
is the capacitor equivalent series resistance.
ESR
Low ESR ceramic capacitors should be used at both the
Atroublesomefeatureinboostmodeistheright-halfplane
zero (RHP), and is given by:
buck-boost regulator output (V
) as well as the buck-
OUT3
boost regulator input supply (V ). Again, only X5R or
IN3
X7R ceramic capacitors should be used because they
retaintheircapacitanceoverwidervoltageandtemperature
rangesthanotherceramictypes.A22µFoutputcapacitoris
sufficient for most applications. The buck-boost regulator
input supply should be bypassed with a 2.2µF capacitor.
Refer to Table 6 for recommended ceramic capacitor
manufacturers.
2
V
IN
fRHPZ
=
Hz
2 • π •IOUT •L • VOUT
The loop gain is typically rolled off before the RHP zero
frequency.
A simple Type I compensation network (as shown in
Figure 8) can be incorporated to stabilize the loop but
at the cost of reduced bandwidth and slower transient
response. To ensure proper phase margin, the loop must
cross unity-gain decade before the LC double pole.
Buck-Boost Regulator Output Voltage Programming
The buck-boost regulator can be programmed for output
voltages greater than 2.75V and less than 5.5V. The full
scaleoutputvoltageisprogrammedusingaresistordivider
The unity-gain frequency of the error amplifier with the
Type I compensation is given by:
from the V
pin connected to the FB3 pin such that:
OUT3
1
R1
R2
fUG
=
Hz
VOUT3 = V
+ 1
FB3
2 • π •R1•CP1
Mostapplicationsdemandanimprovedtransientresponse
toallowasmalleroutputfiltercapacitor.Toachieveahigher
bandwidth, Type III compensation is required. Two zeros
are required to compensate for the double-pole response.
where V is 0.8V. See Figure 8 or 9.
FB3
Type III compensation also reduces any V
seen during a start-up condition.
overshoot
OUT3
358623f
31
LTC3586-2/LTC3586-3
APPLICATIONS INFORMATION
The compensation network depicted in Figure 9 yields the
transfer function:
Recommended Type III Compensation Components for
a 3.3V output:
VC3
R1+ R3
R1: 324k
=
VOUT3 R1•R3 •C1
R : 105k
FB
1
1
C1: 10pF
R2: 15k
s+
• s +
R2 •C2
R1+ R3 •C3
(
)
•
C1+ C2
R2 •C1•C2
1
s • s+
• s +
C2: 330pF
R3: 121k
C3: 33pF
R3 •C3
A Type III compensation network attempts to introduce
a phase bump at a higher frequency than the LC double
pole. This allows the system to cross unity gain after the
LC double pole, and achieve a higher bandwidth. While
attempting to crossover after the LC double pole, the
system must still crossover before the boost right-half
plane zero. If unity gain is not reached sufficiently before
the right-half plane zero, then the –180° of phase from
the LC double pole combined with the –90° of phase from
the right-half plane zero will negate the phase bump of
the compensator.
C : 22µF
OUT
L : 2.2µH
OUT
BOOST REGULATOR APPLICATIONS SECTION
Boost Regulator Inductor Selection
The boost converter is designed to work with inductors in
the range of 1µH to 5µH. For most applications a 2.2µH
inductor will suffice. Larger value inductors will allow
greater output current capability by reducing the inductor
ripple current. However, using too large an inductor may
pushtheright-half-planezerotoofarinsideandcauseloop
instability. Lower value inductors result in higher ripple
current and improved transient response time. Refer to
Table 7 for recommended inductors.
The compensator zeros should be placed either before
or only slightly after the LC double pole such that their
positivephasecontributionsofthecompensationnetwork
offsetthe–180°thatoccursatthefilterdoublepole. Ifthey
are placed at too low of a frequency, however, they will
introduce too much gain to the system and the crossover
frequency will be too high. The two high frequency poles
should be placed such that the system crosses unity gain
during the phase bump introduced by the zeros yet before
the boost right-half plane zero and such that the compen-
sator bandwidth is less than the bandwidth of the error
amp (typically 900kHz). If the gain of the compensation
network is ever greater than the gain of the error amplifier,
then the error amplifier no longer acts as an ideal op amp,
another pole will be introduced where the gain crossover
occurs, and the total compensation gain will not exceed
that of the amplifier.
Boost Regulator Input/Output Capacitor Selection
LowESR(equivalentseriesresistance)ceramiccapacitors
should be used at both the boost regulator output (V
as well as the boost regulator input supply (V ). Only
X5R or X7R ceramic capacitors should be used because
they retain their capacitance over wider voltage and tem-
perature ranges than other ceramic types. At least 10µF of
outputcapacitanceattheratedoutputvoltageisrequiredto
ensure stability of the boost converter output voltage over
the entire temperature and load range. Refer to Table 6 for
recommended ceramic capacitor manufacturers.
)
OUT4
IN4
358623f
32
LTC3586-2/LTC3586-3
APPLICATIONS INFORMATION
Boost Regulator Output Voltage Programming
V
OUT3
0.8V
FB3
+
The boost regulator can be programmed for output volt-
ages up to 5V. The output voltage is programmed using a
ERROR
AMP
R1
–
resistor divider from the V
pin such that:
pin connected to the FB4
OUT4
C
P1
R2
V
C3
358623 F08
R1
R2
V
= V
+ 1
FB4
OUT4
Figure 8. Error Amplifier with Type I Compensation
V
OUT3
where V is 0.8V. See Figure 10.
FB4
Typical values for R1 are in the range of 40k to 1M. Too
small a resistor will result in a large quiescent current
in the feedback network and may hurt efficiency at low
current. Too large a resistor coupled with the FB4 pin ca-
pacitance will create an additional pole which may result
in loop instability. If large values are chosen for R1 and
R3
C3
0.8V
FB3
+
–
R1
ERROR
AMP
C2
R
V
C3
FB
R2
C1
358623 F09
R2, a phase-lead capacitor, C , across resistor R1 can
PL
improve the transient response. Recommended values
Figure 9. Error Amplifier with Type III Compensation
for C are in the range of 2pF to 10pF.
PL
L
Printed Circuit Board Layout Considerations
V
IN4
In order to be able to deliver maximum current under all
conditions,itiscriticalthattheexposedpadonthebackside
of the LTC3586-2/LTC3586-3 packages be soldered to the
PCboardground.Failuretomakethermalcontactbetween
the exposed pad on the backside of the package and the
copper board will result in higher thermal resistances.
SW4
LTC3586-2/
LTC3586-3
V
OUT4
C
R1
C
OUT
PL
FB4
R2
358623 F10
Figure 10. Boost Converter Application Circuit
358623f
33
LTC3586-2/LTC3586-3
APPLICATIONS INFORMATION
Furthermore,duetoitshighfrequencyswitchingcircuitry,
it is imperative that the input capacitors, inductors and
outputcapacitorsbeasclosetotheLTC3586-2/LTC3586-3
as possible and that there be an unbroken ground plane
under the LTC3586-2/LTC3586-3 and all of its external
high frequency components. High frequency currents,
up and radiated emissions will occur. There should be a
group of vias under the grounded backside of the pack-
age leading directly down to an internal ground plane. To
minimize parasitic inductance, the ground plane should
be on the second layer of the PC board.
The GATE pin for the external ideal diode controller has
extremely limited drive current. Care must be taken to
minimize leakage to adjacent PC board traces. 100nA of
leakage from this pin will introduce an offset to the 15mV
ideal diode of approximately 10mV. To minimize leakage,
the trace can be guarded on the PC board by surrounding
such as the V , V , V , V , V
, and V
BUS IN1 IN2
IN3
OUT3
OUT4
currents on the LTC3586-2/LTC3586-3, tend to find their
way along the ground plane in a myriad of paths ranging
from directly back to a mirror path beneath the incident
path on the top of the board. If there are slits or cuts
in the ground plane due to other traces on that layer,
the current will be forced to go around the slits. If high
frequency currents are not allowed to flow back through
their natural least-area path, excessive voltage will build
it with V
connected metal, which should generally be
OUT
less that one volt higher than GATE.
358623 F11
Figure 11. Higher Frequency Ground Currents Follow Their
Incident Path. Slices in the Ground Plane Cause High Voltage
and Increased Emmisions
358623f
34
LTC3586-2/LTC3586-3
PACKAGE DESCRIPTION
Please refer to http://www.linear.com/designtools/packaging/ for the most recent package drawings.
UFE Package
38-Lead Plastic QFN (4mm × 6mm)
(Reference LTC DWG # 05-08-1750 Rev B)
0.70 ±0.05
4.50 ± 0.05
3.10 ± 0.05
2.40 REF
2.65 ± 0.05
4.65 ± 0.05
PACKAGE OUTLINE
0.20 ±0.05
0.40 BSC
4.40 REF
5.10 ± 0.05
6.50 ± 0.05
RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS
APPLY SOLDER MASK TO AREAS THAT ARE NOT SOLDERED
PIN 1 NOTCH
R = 0.30 OR
0.35 × 45°
CHAMFER
R = 0.10
0.75 ± 0.05
2.40 REF
TYP
4.00 ± 0.10
37 38
0.40 ± 0.10
PIN 1
TOP MARK
(NOTE 6)
1
2
4.65 ± 0.10
4.40 REF
6.00 ± 0.10
2.65 ± 0.10
(UFE38) QFN 0708 REV B
0.200 REF
R = 0.115
TYP
0.20 ± 0.05
0.40 BSC
0.00 – 0.05
BOTTOM VIEW—EXPOSED PAD
NOTE:
1. DRAWING IS NOT A JEDEC PACKAGE OUTLINE
2. DRAWING NOT TO SCALE
3. ALL DIMENSIONS ARE IN MILLIMETERS
4. DIMENSIONS OF EXPOSED PAD ON BOTTOM OF PACKAGE DO NOT INCLUDE
MOLD FLASH. MOLD FLASH, IF PRESENT, SHALL NOT EXCEED 0.15mm ON ANY SIDE
5. EXPOSED PAD SHALL BE SOLDER PLATED
6. SHADED AREA IS ONLY A REFERENCE FOR PIN 1 LOCATION
ON THE TOP AND BOTTOM OF PACKAGE
358623f
Information furnished by Linear Technology Corporation is believed to be accurate and reliable.
However, no responsibility is assumed for its use. Linear Technology Corporation makes no representa-
tion that the interconnection of its circuits as described herein will not infringe on existing patent rights.
35
LTC3586-2/LTC3586-3
TYPICAL APPLICATION
Watchdog Microcontroller Operation
L1
3.3µH
35, 36
37
34
USB/WALL
4.5V TO 5.5V
TO OTHER
LOADS
SW
OUT
V
BUS
C1
22µF
V
100k
T
5
29
4
31
32
510Ω
C2
GATE
BAT
NTC
MP1
22µF
PROG
CLPROG
+
2k
Li-Ion
RED
39
GND
0.1µF
2.94k
30
3.3V
1A
CHRG
16, 17
SYSTEM RAIL/
I/O
V
OUT3
10pF
121k
LTC3586-2
LTC3586-3
33pF
330pF
15k
12
11
19
324k
105k
3.3V, 20mA
1µF
22µF
3
V
C3
FB3
LDO3V3
2.2µF
SWCD3
10k
38
L2
2.2µH
13
FAULT
SWAB3
2
HOUSEKEEPING
MICROCONTROLLER
1, 2
9
14, 15
I
V
LIM
IN3
1.8V
L3 4.7µH
400mA
25
SW2
MODE
I/O/MEMORY
MICROPROCESSOR
CORE
1.02M
10pF
23
FB2
10µF
1µF
4
18, 20, 21, 33
6, 7
806k
EN
5V
800mA
24
26
AUDIO/
MOTOR DRIVE
V
V
IN2
OUT4
1.6V
400mA
L4 4.7µH
10pF 88.7k
22µF
SW1
10
FB4
806k
806k
10pF
28
16.9k
FB1
10µF
1µF
27
22
V
IN1
V
IN4
C1, C2: TDK C2012X5R0J226M
10µF
L1: COILCRAFT LPS4018-332LM
L2, L5: TOKO 1098AS-2R2M
L3, L4: TOKO 1098AS-4R7M
MP1: SILICONIX Si2333
L5
2.2µH
8
SW4
358623 TA02
RELATED PARTS
PART NUMBER DESCRIPTION
COMMENTS
2
LTC3555
LTC3556
LTC3566
I C Controlled High Efficiency USB
Maximizes Available Power from USB Port, Bat-Track, “Instant On” Operation, 1.5A Max
Charge Current, 3.3V/25mA Always-On LDO, Three Synchronous Buck Regulators, One 1A
Buck-Boost Regulator, 4mm × 5mm QFN28 Package
Power Manager Plus Triple Step-Down
DC/DC
High Efficiency USB Power Manager Plus Maximizes Available Power from USB Port, Bat-Track, “Instant On” Operation, 1.5A Max
Dual Buck Plus Buck-Boost DC/DC
Charge Current, 3.3V/25mA Always-On LDO, Two 400mA Synchronous Buck Regulators,
One 1A Buck-Boost Regulator, 4mm × 5mm QFN28 Package
Switching USB Power Manager with
Li-Ion/Polymer Charger, 1A Buck-Boost
Converter Plus LDO
Multifunction PMIC: Switchmode Power Manager and 1A Buck-Boost Regulator + LDO,
Charge Current Programmable Up to 1.5A from Wall Adapter Input, Thermal Regulation
Synchronous Buck-Boost Converters Efficiency: >95%, 4mm × 4mm QFN24 Package
LTC3586/
LTC3586-1
Switching USB Power Manager with
Complete Multifunction PMIC: Switching Power Manager, 1A Buck-Boost + 2 Bucks +
Li-Ion/Polymer Charger, 1A Buck-Boost + Boost + LDO, Synchronous Buck/Buck-Boost Converter Efficiency: >95%; Charge Current
Dual Sync Buck Converter + Boost + LDO 1.5A; LTC3586-1 version has 4.1V V
; 4mm × 6mm QFN-38 Package
FLOAT
358623f
LT 0312 • PRINTED IN USA
36 LinearTechnology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
●
●
LINEAR TECHNOLOGY CORPORATION 2012
(408) 432-1900 FAX: (408) 434-0507 www.linear.com
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