LTC3559EUD [Linear]
IC 1.05 A BATTERY CHARGE CONTROLLER, 2590 kHz SWITCHING FREQ-MAX, PQCC16, 3 X 3 MM, PLASTIC, MO-220WEED-2, QFN-16, Switching Regulator or Controller;
| 型号： | LTC3559EUD |
| 厂家： | 
Linear |
| 描述： | IC 1.05 A BATTERY CHARGE CONTROLLER, 2590 kHz SWITCHING FREQ-MAX, PQCC16, 3 X 3 MM, PLASTIC, MO-220WEED-2, QFN-16, Switching Regulator or Controller 开关 |
| 文件： | 总24页 (文件大小：302K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
LTC3559
Linear USB Battery Charger
with Dual Buck Regulators
FEATURES
DESCRIPTION
The LTC®3559 is a USB battery charger with dual high ef-
ficiencybuckregulators.Thepartisideallysuitedtopower
single cell Li-Ion/Polymer based handheld applications
needing multiple supply rails.
Battery Charger
■
Standalone USB Charger
■
Up to 950mA Charge Current Programmable via
Single Resistor
■
HPWR Input Selects 20% or 100% of Programmed
Battery charge current is programmed via the PROG pin
and the HPWR pin, with capability up to 950mA at the BAT
pin. The battery charger has an NTC input for temperature
qualified charging. The CHRG pin allows battery status to
be monitored continuously during the charging process.
An internal timer controls charger termination.
Charge Current
■
NTC Input for Temperature Qualified Charging
■
Internal Timer Termination
⎯
⎯
⎯
⎯
■
Bad Battery Detection
■
⎯
⎯
⎯
⎯
CHRG indicates C/10 or Timeout
Buck Regulators
Each monolithic synchronous buck regulator provides up
to 400mA of output current while operating at efficiencies
greater than 90% over the entire Li-Ion/Polymer range.
A MODE pin provides the flexibility to place both buck
regulators in a power saving Burst Mode operation or a
low noise pulse skip mode.
■
400mA Output Current
■
2.25MHz Constant Frequency Operation
■
Zero Current in Shutdown
Low Noise Pulse Skip Operation or Power Saving
Burst Mode Operation
Low No Load Quiescent Current: 35μA
■
■
TheLTC3559isofferedinalowprofilethermallyenhanced
16-lead (3mm × 3mm) QFN package.
, LT, LTC, LTM and Burst Mode are registered trademarks of Linear Technology
Corporation. All other trademarks are the property of their respective owners.
■
Available in a Low Profile Thermally Enhanced
16-Lead 3mm × 3mm QFN Package
APPLICATIONS
■
SD/Flash-Based MP3 Players
Low Power Handheld Applications
■
TYPICAL APPLICATION
USB Charger Plus Dual Buck Regulators
UP TO 500mA
USB (4.3V TO 5.5V)
OR AC ADAPTOR
V
CC
BAT
SINGLE
Li-lon CELL
(2.7V TO 4.2V)
+
1μF
PV
IN
2.2μF
NTC
LTC3559
4.7μH
1.74k
2.5V
PROG
SW1
FB1
400mA
22pF
655k
309k
10μF
CHRG
SUSP
HPWR
EN1
DIGITAL
CONTROL
4.7μH
1.2V
400mA
SW2
FB2
22pF
324k
10μF
EN2
649k
MODE
GND
EXPOSED
PAD
3559 TA01
3559f
1
LTC3559
ABSOLUTE MAXIMUM RATINGS
PACKAGE/ORDER INFORMATION
(Note 1)
TOP VIEW
V
(Transient);
CC
t< 1ms and duty cycle< 1%.......................... –0.3V to 7V
(Static) .................................................. –0.3V to 6V
16 15 14 13
V
CC
GND
BAT
1
2
3
4
12 HPWR
11 SUSP
BAT, CHRG, SUSP........................................ –0.3V to 6V
17
HPWR, NTC, PROG.......–0.3V to Max (V , BAT) + 0.3V
CC
MODE
FB1
FB2
EN2
10
9
PROG Pin current................................................1.25mA
BAT Pin Current ..........................................................1A
5
6
7
8
PV ................................................ –0.3V to BAT + 0.3V
IN
EN1, EN2, MODE.......................................... –0.3V to 6V
UD PACKAGE
16-LEAD (3mm × 3mm) PLASTIC QFN
= 125°C, θ = 68°C/W
FB1, FB2, SW1, SW2 ............–0.3V to PV + 0.3V or 6V
IN
T
JMAX
JA
EXPOSED PAD (PIN 17) IS GND, MUST BE SOLDERED TO PCB
I
, I
......................................................600mA DC
SW1 SW2
Junction Temperature (Note 2) ............................. 125°C
Operating Temperature Range (Note 3) ... –40°C to 85°C
Storage Temperature.............................. –65°C to 125°C
ORDER PART NUMBER
LTC3559EUD
UD PART MARKING
LCMB
Order Options Tape and Reel: Add #TR
Lead Free: Add #PBF Lead Free Tape and Reel: Add #TRPBF
Lead Free Part Marking: http://www.linear.com/leadfree/
Consult LTC Marketing for parts specified with wider operating temperature ranges.
ELECTRICAL CHARACTERISTICS The ● denotes specifications that apply over the full operating temperature
range, otherwise specifications are at TA = 25°C.
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
Battery Charger. V = 5V, BAT = PV = 3.6V, R
= 1.74k, HPWR = 5V, SUSP = NTC = EN1 = EN2 = 0V
CC
IN
PROG
●
●
V
Input Supply Voltage
4.3
5.5
V
CC
I
Battery Charger Quiescent Current (Note 4) Standby Mode, Charge Terminated
Suspend Mode, V = 5V
200
8.5
4.200
4.200
460
92
–3.5
–2.5
–1.5
400
17
4.221
4.235
500
100
–7
–4
–3
μA
μA
V
V
mA
mA
μA
μA
μA
VCC
SUSP
V
BAT Regulated Output Voltage
Constant Current Mode Charge Current
Battery Drain Current
4.179
4.165
440
84
FLOAT
0°C ≤ T ≤ 85°C
HPWR = 5V
HPWR = 0V
A
I
I
CHG
Standby Mode, Charger Terminated
Shutdown, V < V , BAT = 4.2V
BAT
CC
UVLO
Suspend Mode, SUSP = 5V, BAT = 4.2V
V
Undervoltage Lockout Threshold
Undervotlage Lockout Hystersis
BAT = 3.5V, V Rising
3.85
30
4.0
200
50
4.125
V
mV
mV
UVLO
CC
ΔV
BAT = 3.5V
UVLO
V
Differential Undervoltage Lockout
Threshold
BAT = 4.2V, (V – BAT) Falling
70
DUVLO
CC
ΔV
DUVLO
Differential Undervoltage Lockout
Hysteresis
BAT = 4.2V
130
mV
V
PROG
PROG Pin Servo Voltage
HPWR = 5V
HPWR = 0V
1.000
0.200
0.100
V
V
V
BAT < V
TRKL
h
Ratio of I to PROG Pin Current
800
mA/mA
PROG
BAT
I
Trickle Charge Current
BAT < V
36
46
56
mA
TRKL
TRKL
V
Trickle Charge Threshold Voltage
BAT Rising
2.8
2.9
3.0
V
TRKL
3559f
2
LTC3559
ELECTRICAL CHARACTERISTICS The ● denotes specifications that apply over the full operating temperature
range, otherwise specifications are at TA = 25°C.
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
ΔV
ΔV
Trickle Charge Hysteresis Voltage
100
mV
TRKL
Recharge Battery Threshold Voltage
Recharge Comparator Filter Time
Safety Timer Termination Period
Bad Battery Termination Time
Threshold Voltage Relative to V
BAT Falling
–85
–100
1.7
4
–130
mV
ms
RECHRG
FLOAT
t
t
t
RECHRG
BAT = V
BAT < V
3.5
0.4
4.5
0.6
Hour
Hour
mA/mA
ms
TERM
FLOAT
TRKL
0.5
0.1
2.2
500
BADBAT
h
End-of-Charge Indication Current Ratio
End-of-Charge Comparator Filter Time
(Note 5)
I Falling
BAT
0.085
0.11
C/10
C/10
t
R
Battery Charger Power FET On-Resistance I = 190mA
mΩ
ON(CHG)
BAT
(Between V and BAT)
CC
T
Junction Temperature in Constant
Temperature Mode
105
°C
LIM
NTC
V
V
V
Cold Temperature Fault Threshold Voltage Rising NTC Voltage
Hysteresis
Hot Temperature Fault Threshold Voltage Falling NTC Voltage
Hysteresis
75
33.4
0.7
–1
76.5
1.6
34.9
1.6
1.7
50
78
36.4
2.7
1
%V
%V
%VCC
%VCC
%V
CC
mV
μA
COLD
HOT
DIS
CC
CC
●
NTC Disable Threshold Voltage
Falling NTC Voltage
Hysteresis
I
NTC Leakage Current
⎯ ⎯ ⎯ ⎯
V
= V = 5V
NTC CC
NTC
Logic (HPWR, SUSP, CHRG)
V
V
Input Low Voltage
HPWR, SUSP Pins
HPWR, SUSP Pins
HPWR, SUSP Pins
0.4
V
V
IL
Input High Voltage
1.2
1.9
IH
●
R
V
Logic Pin Pull-Down Resistance
⎯ ⎯ ⎯ ⎯
4
100
0
6.3
250
1
MΩ
mV
μA
DN
CHRG Pin Output Low Voltage
⎯ ⎯ ⎯ ⎯
I
= 5mA
⎯
CHRG
⎯
⎯
⎯
⎯
⎯
⎯
⎯
CHRG
I
CHRG Pin Input Current
BAT = 4.5V, V
= 5V
⎯
CHRG
⎯
⎯
⎯
⎯
⎯
⎯
⎯
CHRG
Buck Switching Regulators, BAT = PV = 3.8V, EN1 = EN2 = 3.8V
IN
●
●
PV
Input Supply Voltage
3
4.2
V
IN
I
Pulse Skip Supply Current
Burst Mode Supply Current
Shutdown Supply Current
Supply Current in UVLO
V
V
= 0.82V, MODE = 0 (One Buck Enabled) (Note 6)
= 0.82V, MODE = 1 (One Buck Enabled) (Note 6)
220
35
0
400
50
2
μA
μA
μA
μA
PVIN
FB
FB
EN1 = EN2 = 0V
PV = 2.0V
4
8
IN
PV UVLO PV Falling
2.45
2.55
V
V
IN
IN
PV Rising
IN
f
Switching Frequency
MODE = 0V
1.91
2.25
2.59
0.4
MHz
OSC
V
Input Low Voltage
MODE, EN1, EN2
MODE, EN1, EN2
MODE = 0V or 3.8V
MODE = 0V or 3.8V
V
IL
V
Input High Voltage
Peak PMOS Current Limit
Available Output Current
Feedback Voltage
1.2
550
V
IH
I
I
800
800
1050
mA
mA
mV
μA
%
LIMSW
OUT
400
●
V
780
820
FB
I
FB Input Current
FB1, FB2 = 0.82V
FB1, FB2 = 0V
–0.05
100
0.05
FB
D
R
R
R
Maximum Duty Cycle
MAX
Ω
R
DS(ON)
R
DS(ON)
of PMOS
of NMOS
I
I
= 100mA
0.65
0.75
13
PMOS
NMOS
SW(PD)
SW
SW
Ω
= –100mA
SW Pull-Down in Shutdown
kΩ
3559f
3
LTC3559
ELECTRICAL CHARACTERISTICS
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.
are assured by design, characterization and correlation with statistical
process controls.
Note 4: V supply current does not include current through the PROG pin
CC
or any current delivered to the BAT pin. Total input current is equal to this
Note 2: T is calculated from the ambient temperature T and power
specification plus 1.00125 • I where I is the charge current.
J
A
BAT BAT
dissipation P according to the following formula:
D
Note 5: I
is expressed as a fraction of measured full charge current
C/10
T = T + (P • θ °C/W)
with indicated PROG resistor.
J
A
D
JA
Note 3: The LTC3559 is guaranteed to meet specifications from 0°C to
85°C. Specifications over the –40°C to 85°C operating temperature range
Note 6: Dynamic supply current is higher due to the gate charge being
delivered at the switching frequency.
TYPICAL PERFORMANCE CHARACTERISTICS
Battery Regulation (Float) Voltage
vs Battery Charge Current,
Constant Voltage Charging
Suspend State Supply and BAT
Currents vs Temperature
Battery Regulation (Float)
Voltage vs Temperature
10
9
8
7
6
5
4
3
2
1
0
4.205
4.200
4.195
4.190
4.185
4.180
4.175
4.170
4.165
4.160
4.155
4.150
4.24
V
= 5V
CC
4.23
4.22
I
VCC
4.21
4.20
4.19
4.18
4.17
V
= 5V
CC
BAT = 4.2V
SUSP = 5V
EN1 = EN2 = 0V
V
= 5V
CC
I
BAT
HPWR = 5V
R
= 845Ω
PROG
EN1 = EN2 = 0V
4.16
0
100 200 300 400 500 600 700 800 9001000
–55
–15
5
25
45
65
85
–55
–35 –15
5
25
45
65
85
–35
TEMPERATURE (°C)
I
(mA)
TEMPERATURE (°C)
BAT
3559 G03
3559 G01
3559 G02
Battery Charge Current vs
Ambient Temperature in Thermal
Regulation
Battery Charge Current
vs Supply Voltage
Battery Charge Current
vs Battery Voltage
500
495
490
485
480
475
470
465
460
455
450
445
440
500
450
400
350
300
250
200
150
100
50
500
450
400
350
300
250
200
150
100
50
HPWR = 5V
V
= 5V
V
= 5V
PROG
CC
CC
HPWR = 5V
= 1.74k
R
= 1.74k
R
PROG
EN1 = EN2 = 0V
V
= 5V
HPWR = 0V
CC
HPWR = 5V
= 1.74k
R
PROG
EN1 = EN2 = 0
0
0
4.3 4.4
4.6
4.8 4.9 5.0 5.1 5.2 5.3 5.4 5.5
4.7
4.5
2
2.5
3
V
3.5
(V)
4
4.5
–55 –35 –15
5
25 45 65 85 105 125
V
(V)
TEMPERATURE (°C)
CC
BAT
3559 G04
3559 G05
3559 G06
3559f
4
LTC3559
TYPICAL PERFORMANCE CHARACTERISTICS
Battery Drain Current in
Undervoltage Lockout vs
Temperature
PROG Voltage
vs Battery Charge Current
Battery Charger Undervoltage
Lockout Threshold vs Temperature
4.2
4.1
1.2
1.0
3.0
2.5
2.0
1.5
BAT = 3.5V
V
= 5V
EN1 = EN2 = 0V
CC
HPWR = 5V
R
= 1.74k
PROG
RISING
EN1 = EN2 = 0V
BAT = 4.2
4.0
3.9
3.8
3.7
3.6
0.8
0.6
BAT = 3.6
FALLING
0.4
0.2
0
1.0
0.5
0
3.5
25
TEMPERATURE (°C)
65
85
–55 –35 –15
5
45
0
50 100 150 200 250 300 350 400 450 500
25
TEMPERATURE (°C)
65
85
–55 –35 –15
5
45
I
(mA)
BAT
3559 G07
3559 G09
3559 G08
Recharge Threshold
vs Temperature
Battery Charger FET
On-Resistance vs Temperature
SUSP/HPWR Pin Rising
Thresholds vs Temperature
115
111
107
103
99
1.2
700
650
600
550
500
450
400
350
300
V = 5V
CC
V
= 5V
V
BAT
EN1 = EN2 = 0V
= 4V
CC
CC
I
= 200mA
1.1
1.0
0.9
0.8
0.7
0.6
0.5
95
91
87
83
79
0.4
75
–35 –15
25
45
65
85
–55
5
–55
–15
5
25
45
65
85
–35
–15
5
25
45
65
85
–55 –35
TEMPERATURE (°C)
TEMPERATURE (°C)
TEMPERATURE (°C)
3559 G12
3559 G10
3559 G11
⎯ ⎯ ⎯ ⎯
CHRG Pin Output Low Voltage
vs Temperature
⎯ ⎯ ⎯ ⎯
CHRG Pin I-V Curve
Timer Accuracy vs Supply Voltage
2.0
1.5
1.0
0.5
0
70
60
50
40
30
20
10
0
140
120
V
= 5V
V
CHRG
= 5V
CC
CC
BAT = 3.8V
I
= 5mA
100
80
60
40
–0.5
–1.0
20
0
4.3
4.7
4.9
(V)
5.1
5.3
5.5
25
TEMPERATURE (°C)
65
85
4
6
4.5
–55 –35 –15
5
45
0
1
2
3
5
V
CHRG (V)
CC
3559 G15
3559 G13
3559 G14
3559f
5
LTC3559
TYPICAL PERFORMANCE CHARACTERISTICS
Buck Regulator Input Current vs
Temperature, Burst Mode Operation
Complete Charge Cycle
2400mAh Battery
Timer Accuracy vs Temperature
50
45
7
6
1000
800
600
400
200
0
V
= 5V
V
= 0.82V
CC
V
= 5V
CC
PROG
FB
R
= 0.845k
HPWR = 5V
5
40
4
5.0
4.5
4.0
3.5
3.0
5.0
4.0
3.0
2.0
1.0
0
PV = 4.2V
IN
3
35
30
2
PV = 2.7V
IN
1
0
25
20
–1
–2
–55 –35 –15
5
25 45 65 85 105 125
0
1
2
3
4
5
6
–55 –35 –15
5
85
25
45
65
TEMPERATURE (°C)
TEMPERATURE (°C)
TIME (HOUR)
3559 G17
3559 G18
3559 G16
Buck Regulator Input Current vs
Temperature, Pulse Skip Mode
Buck Regulator PVIN Undervoltage
Thresholds vs Temperature
Frequency vs Temperature
2.5
2.4
2.3
2.2
2.1
2.0
1.9
1.8
1.7
1.6
1.5
2.85
2.75
400
350
PV = 3.8V
IN
V
= 0.82V
FB
2.65
300
PV = 4.2V
IN
RISING
2.55
2.45
250
200
PV = 2.7V
IN
FALLING
2.35
2.25
150
100
–55
45
TEMPERATURE (°C)
85 105
125
–55 –35 –15
5
25 45 65 85 105 125
–35 –15
5
25
65
–55 –35 –15
5
25 45 65 85 105 125
TEMPERATURE (°C)
TEMPERATURE (°C)
3559 G21
3559 G20
3559 G19
Buck Regulator PMOS RDS(0N) vs
Temperature
Buck Regulator NMOS RDS(0N) vs
Temperature
Buck Regulator Enable
Thresholds vs Temperature
1300
1200
1100
1000
900
1300
1200
1100
1000
900
1200
1100
1000
900
PV = 3.8V
IN
PV = 2.7V
IN
PV = 2.7V
IN
800
800
800
RISING
PV = 4.2V
IN
PV = 4.2V
IN
700
700
700
FALLING
600
600
600
500
500
500
400
400
400
–55 –35 –15
5
25 45
125
–55 –35 –15
5
25 45
125
65 85 105
25 45
65 85 105
–55 –35 –15
5
65 85 105 125
TEMPERATURE (°C)
TEMPERATURE (°C)
TEMPERATURE (°C)
3559 G23
3559 G24
3559 G22
3559f
6
LTC3559
TYPICAL PERFORMANCE CHARACTERISTICS
Buck Regulator Efficiency vs ILOAD
Buck Regulator Load Regulation
100
90
80
70
60
50
40
30
20
10
0
2.60
2.58
2.56
2.54
2.52
2.50
2.48
2.46
2.44
Burst Mode
OPERATION
PV = 3.8V
IN
OUT
V
= 2.5V
PULSE SKIP
MODE
Burst Mode
OPERATION
PULSE SKIP
MODE
V
= 2.5V
OUT
IN
PV = 4.2V
0.1
1
10
(mA)
100
1000
1
10
100
1000
I
LOAD
I
(mA)
LOAD
3559 G25
3559 G26
Buck Regulator Line Regulation
Buck Regulator Efficiency vs ILOAD
100
90
80
70
60
50
40
30
20
10
0
2.60
2.58
2.56
2.54
V
LOAD
= 2.5V
= 200mA
OUT
Burst Mode
OPERATION
I
PULSE SKIP
MODE
2.52
2.50
2.48
2.46
2.44
V
= 1.2V
OUT
PV = 2.7V
IN
PV = 4.2V
IN
3.0
3.3
PV (V)
3.9
0.1
1
10
(mA)
100
1000
2.7
4.2
3.6
I
LOAD
IN
3559 G28
3559 G27
Buck Regulator Load Regulation
Buck Regulator Line Regulation
1.25
1.24
1.23
1.22
1.21
1.20
1.19
1.18
1.17
1.16
1.15
1.25
1.24
1.23
1.22
PV = 3.8V
IN
V
I
= 1.2V
= 200mA
OUT
LOAD
V
= 1.2V
OUT
Burst Mode
OPERATION
1.21
1.20
PULSE SKIP
MODE
1.19
1.18
1.17
1.16
1.15
2.7
3.0
3.3
3.6
3.9
4.2
1
10
100
1000
PV (V)
IN
I
(mA)
LOAD
3559 G29
3559 G30
3559f
7
LTC3559
TYPICAL PERFORMANCE CHARACTERISTICS
Buck Regulator Pulse Skip Mode
Operation
Buck Regulator Start-Up Transient
V
V
OUT
OUT
20mV/DIV (AC)
500mV/DIV
SW
2V/DIV
INDUCTOR
CURRENT
= 200mA/DIV
I
L
INDUCTOR
CURRENT
= 50mA/DIV
EN
2V/DIV
I
L
3559 G34
3559 G33
PV = 3.8V
IN
LOAD = 10mA
200ns/DIV
PV = 3.8V
IN
50 s/DIV
PULSE SKIP MODE
LOAD = 6
Buck Regulator Burst Mode
Operation
Buck Regulator Transient
Response, Pulse Skip Mode
INDUCTOR
CURRENT
= 200mA/DIV
V
OUT
20mV/DIV (AC)
I
L
SW
2V/DIV
V
OUT
50mV/DIV (AC)
INDUCTOR
CURRENT
= 60mA/DIV
LOAD STEP
5mA TO 290mA
I
L
3559 G35
3559 G36
PV = 3.8V
IN
LOAD = 60mA
2 s/DIV
PV = 3.8V
IN
50 s/DIV
Buck Regulator Transient
Response, Burst Mode Operation
INDUCTOR
CURRENT
= 200mA/DIV
I
L
V
OUT
50mV/DIV (AC)
LOAD STEP
5mA TO 290mA
3559 G37
PV = 3.8V
IN
50μs/DIV
3559f
8
LTC3559
PIN FUNCTIONS
GND (Pin1): Ground, Connect to Exposed Pad (Pin 17).
USB specification. A weak pull-down current is internally
applied to this pin to ensure it is low at power up when
the input is not being driven externally.
BAT (Pin 2): Charge Current Output. Provides charge cur-
rent to the battery and regulates final float voltage to 4.2V.
NTC (Pin 13): Input to the NTC Thermistor Monitoring
Circuit. The NTC pin connects to a negative temperature
coefficient thermistor which is typically co-packaged with
the battery pack to determine if the battery is too hot or
too cold to charge. If the battery temperature is out of
range, charging is paused until the battery temperature
re-enters the valid range. A low drift bias resistor is re-
MODE (Pin 3): MODE Pin for Buck Regulators. When held
high, both regulators are in Burst Mode operation. When
held low both regulators operate in pulse skip mode. This
pin is a high impedance input; do not float.
FB1 (Pin 4): Buck 1 Feedback Voltage Pin. Receives feed-
back by a resistor divider connected across the output.
quired from V to NTC and a thermistor is required from
CC
EN1 (Pin 5): Enable Input Pin for Buck 1. This pin is a high
impedance input; do not float. Active high.
NTC to ground. To disable the NTC function, the NTC pin
should be grounded.
SW1 (Pin 6): Buck 1 Switching Node. External inductor
connects to this node.
PROG (Pin 14): Charge Current Program and Charge
Current Monitor Pin. Charge current is programmed by
connectingaresistorfromPROGtoground.Whencharging
in constant current mode, the PROG pin servos to 1V if
the HPWR pin is pulled high, or 200mV if the HPWR pin
is pulled low. The voltage on this pin always represents
the battery current through the following formula:
PV (Pin 7): Input Supply Pin for Buck Regulators.
IN
Connect to BAT. A 2.2μF decoupling capacitor to GND is
recommended.
SW2 (Pin 8): Buck 2 Switching Node. External inductor
connects to this node.
PROG
RPROG
EN2 (Pin 9): Enable Input Pin for Buck 2. This pin is a high
impedance input; do not float. Active high.
IBAT
=
•800
FB2(Pin10):Buck2FeedbackVoltagePin.Receivesfeed-
⎯ ⎯ ⎯ ⎯
CHRG (Pin 15): Open-Drain Charge Status Output. The
back by a resistor divider connected across the output.
⎯
⎯
⎯
⎯
CHRG pin indicates the status of the battery charger. Four
SUSP (Pin 11): Suspend Battery Charging Operation.
A voltage greater than 1.2V on this pin puts the battery
charger into suspend mode, disables the charger and
resets the termination timer. A weak pull-down current is
internally applied to this pin to ensure it is low at power
up when the input is not being driven externally.
⎯
⎯
⎯
⎯
possible states are represented by CHRG: charging, not
charging (i.e., the charge current is less than 1/10th of the
full-scale charge current), unresponsive battery (i.e., the
batteryvoltageremainsbelow2.9Vafter1/2hourofcharg-
⎯
⎯
⎯
⎯
ing) and battery temperature out of range. CHRG requires
a pull-up resistor and/or LED to provide indication.
HPWR (Pin 12): High Current Battery Charging Enabled.
A voltage greater than 1.2V at this pin programs the
BAT pin current at 100% of the maximum programmed
charge current. A voltage less than 0.4V sets the BAT pin
current to 20% of the maximum programmed charge
current. When used with a 1.74k PROG resistor, this pin
can toggle between low power and high power modes per
V
(Pin 16): Battery Charger Input. A 1μF decoupling
CC
capacitor to GND is recommended.
Exposed Pad (Pin 17): Ground. The Exposed Pad must
be soldered to PCB ground to provide electrical contact
and rated thermal performance.
3559f
9
LTC3559
BLOCK DIAGRAM
16
V
CC
V
IN
BAT
BODY
1x
800x
MAXER
BAT
2
–
+
CHRG
15
HPWR
12
CA
TA
LOGIC
SUSP
11
T
DIE
PROG
14
NTCA
NTC
13
NTC REF
BATTERY CHARGER
PV
IN
7
MODE
3
EN1
5
UNDERVOLTAGE
LOCKOUT
EN2
9
EN MODE
CLK
V
–
+
FB1
4
FB
SW1
CONTROL
LOGIC
6
V
C
G
OT
m
DIE
0.8V
T
TEMPERATURE
DIE
BUCK REGULATOR 1
V
BANDGAP
REF
OSCILLATOR
2.25MHz
CLK
EN MODE
CLK
V
–
+
FB2
FB
SW2
CONTROL
LOGIC
10
8
V
C
G
m
0.8V
BUCK REGULATOR 2
GND
1
EXPOSED PAD
17
3559 BD
3559f
10
LTC3559
OPERATION
at the BAT pin via a single PROG resistor. The actual BAT
pin current is set by the status of the HPWR pin.
TheLTC3559isalinearbatterychargerwithdualmonolithic
synchronous buck regulators. The buck regulators are
internally compensated and need no external compensa-
tion components.
For proper operation, the BAT and PV pins must be tied
IN
together. If a buck regulator is also enabled during the
battery charging operation, the net current charging the
battery may be lower than the actual programmed value.
Refer to Figure 1 for an explanation.
Thebatterychargeremploysaconstant-currentconstant-
voltage charging algorithm and is capable of charging a
singleLi-Ionbatteryatchargingcurrentsupto950mA.The
usercanprogramthemaximumchargingcurrentavailable
500mA 300mA
USB (5V)
V
BAT
CC
SINGLE Li-lon
CELL 3.6V
+
PV
IN
200mA
PROG
SUSP
+
R
PROG
2.2 F
1.62k
LTC3559
HIGH
V
HPWR
EN1
SW1
SW2
OUT1
HIGH
HIGH
V
OUT2
EN2
LOW (PULSE SKIP MODE)
MODE
3559 F01
Figure 1. Current Being Delivered at the BAT Pin is 500mA. Both Buck Regulators are Enabled. The Sum of the
Average Input Currents Drawn by Both Buck Regulators is 200mA. This Makes the Effective Battery Charging Current
only 300mA. If the HPWR Pin Were Tied LO, the BAT Pin Current Would be 100mA.With the Buck Regulator
Conditions Unchanged, this Would Cause the Battery to Discharge at 100mA
APPLICATIONS INFORMATION
Battery Charger Introduction
Input Current vs Charge Current
The LTC3559 has a linear battery charger designed to
charge single-cell lithium-ion batteries. The charger uses
a constant current/constant voltage charge algorithm
with a charge current programmable up to 950mA. Ad-
ditional features include automatic recharge, an internal
terminationtimer,low-batterytricklechargeconditioning,
bad-battery detection, and a thermistor sensor input for
out of temperature charge pausing.
The battery charger regulates the total current delivered
to the BAT pin; this is the charge current. To calculate the
total input current (i.e., the total current drawn from the
V
pin), it is necessary to sum the battery charge current,
CC
charger quiescent current and PROG pin current.
Undervoltage Lockout (UVLO)
The undervoltage lockout circuit monitors the input volt-
age (V ) and disables the battery charger until V rises
Futhermore, the battery charger is capable of operating
from a USB power source. In this application, charge
current can be programmed to a maximum of 100mA or
500mA per USB power specifications.
CC
CC
above V
(typically 4V). 200mV of hysteresis prevents
UVLO
oscillations around the trip point. In addition, a differential
undervoltage lockout circuit disables the battery charger
when V falls to within V
(typically 50mV) of the
DUVLO
CC
BAT voltage.
3559f
11
LTC3559
APPLICATIONS INFORMATION
Suspend Mode
After the safety timer expires, charging of the battery will
discontinue and no more current will be delivered.
The battery charger can also be disabled by pulling the
SUSP pin above 1.2V. In suspend mode, the battery
drain current is reduced to 1.5μA and the input current is
reduced to 8.5μA.
Automatic Recharge
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 au-
tomatically begin when the battery voltage falls below
Charge Cycle Overview
When a battery charge cycle begins, the battery charger
first determines if the battery is deeply discharged. If the
batteryvoltageisbelowV ,typically2.9V,anautomatic
TRKL
V
(typically 4.1V). In the event that the safety timer
RECHRG
trickle charge feature sets the battery charge current to
10% of the full-scale value.
is running when the battery voltage falls below V
, it
RECHRG
will reset back to zero. To prevent brief excursions below
fromresettingthesafetytimer,thebatteryvoltage
V
RECHRG
must be below V
Once the battery voltage is above 2.9V, the battery char-
ger begins charging in constant current mode. When the
battery voltage approaches the 4.2V required to maintain
a full charge, otherwise known as the float voltage, the
charge current begins to decrease as the battery charger
switches into constant voltage mode.
for more than 1.7ms. The charge
RECHRG
cycle and safety timer will also restart if the V UVLO or
CC
DUVLO cycles low and then high (e.g., V is removed
CC
and then replaced) or the charger enters and then exits
suspend mode.
Programming Charge Current
Trickle Charge and Defective Battery Detection
The PROG pin serves both as a charge current program
pin, and as a charge current monitor pin. By design, the
PROG pin current is 1/800th of the battery charge current.
Therefore, connecting a resistor from PROG to ground
programsthechargecurrentwhilemeasuringthePROGpin
voltage allows the user to calculate the charge current.
Any time the battery voltage is below V
goes into trickle charge mode and reduces the charge
current to 10% of the full-scale current. If the battery
, the charger
TRKL
voltage remains below V
for more than 1/2 hour, the
TRKL
chargerlatchesthebad-batterystate, automaticallytermi-
⎯
⎯
⎯
⎯
nates, and indicates via the CHRG pin that the battery was
unresponsive. If for any reason the battery voltage rises
Full-scalechargecurrentisdefinedas100%oftheconstant
current mode charge current programmed by the PROG
resistor.Inconstantcurrentmode,thePROGpinservosto
1V if HPWR is high, which corresponds to charging at the
full-scale charge current, or 200mV if HPWR is low, which
corresponds to charging at 20% of the full-scale charge
current. Thus, the full-scale charge current and desired
program resistor for a given full-scale charge current are
calculated using the following equations:
above V , the charger will resume charging. Since the
TRKL
charger has latched the bad-battery state, if the battery
voltagethenfallsbelowV againbutwithoutrisingpast
TRKL
V
first, the charger will immediately assume that
RECHRG
the battery is defective. To reset the charger (i.e., when
the dead battery is replaced with a new battery), simply
remove the input voltage and reapply it or put the part in
and out of suspend mode.
800V
RPROG
Charge Termination
ICHG
=
The battery charger has a built-in safety timer that sets
the total charge time for 4 hours. Once the battery volt-
800V
ICHG
RPROG
=
age rises above V
(typically 4.1V) and the charger
RECHRG
enters constant voltage mode, the 4-hour timer is started.
3559f
12
LTC3559
APPLICATIONS INFORMATION
In any mode, the actual battery current can be determined
by monitoring the PROG pin voltage and using the follow-
ing equation:
charge current has dropped to below 10% of the full-scale
⎯
⎯
⎯
⎯
current, the CHRG pin is released (high impedance). If a
⎯
⎯
⎯
⎯
fault occurs after the CHRG pin is released, the pin re-
mains high impedance. However, if a fault occurs before
PROG
RPROG
IBAT
=
•800
⎯
⎯
⎯
⎯
the CHRG pin is released, the pin is switched at 35kHz.
Whileswitching,itsdutycycleismodulatedbetweenahigh
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
microprocessor recognition.
Thermal Regulation
To prevent thermal damage to the IC or surrounding
components, an internal thermal feedback loop will auto-
matically decrease the programmed charge current if the
die temperature rises to approximately 115°C. Thermal
regulation protects the battery charger from excessive
temperature due to high power operation or high ambient
thermal conditions and allows the user to push the limits
of the power handling capability with a given circuit board
design without risk of damaging the LTC3559 or external
components. The benefit of the LTC3559 battery charger
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 automatically reduce the current in worst-case con-
ditions.
⎯ ⎯ ⎯ ⎯
Table 1 illustrates the four possible states of the CHRG
pin when the battery charger is active.
⎯ ⎯ ⎯ ⎯
Table 1. CHRG Output Pin
MODULATION
(BLINK)
STATUS
FREQUENCY
0Hz
FREQUENCY
DUTY CYCLE
100%
Charging
0 Hz (Lo-Z)
0 Hz (Hi-Z)
I
< C/10
0Hz
0%
BAT
35kHz
35kHz
1.5Hz at 50%
6.1Hz at 50%
6.25% to 93.75%
12.5% to 87.5%
NTC Fault
Bad Battery
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.
Charge Status Indication
⎯ ⎯ ⎯ ⎯
The CHRG pin indicates the status of the battery charger.
⎯
⎯
⎯
⎯
Four possible states are represented by CHRG: charging,
notcharging,unresponsivebatteryandbatterytemperature
out of range.
If a battery is found to be unresponsive to charging (i.e.,
⎯ ⎯ ⎯ ⎯
ThesignalattheCHRGpincanbeeasilyrecognizedasone
of the above four states by either a human or a micropro-
its voltage remains below V
for over 1/2 hour), the
TRKL
⎯
⎯
⎯
⎯
CHRG pin gives the battery fault indication. For this fault,
a human would easily recognize the frantic 6.1Hz “fast”
blinking of the LED while a microprocessor would be able
to decode either the 12.5% or 87.5% duty cycles as a bad
battery fault.
⎯
⎯
⎯
⎯
cessor. The CHRG pin, which is an open-drain output, can
drive an indicator LED through a current limiting resistor
for human interfacing, or simply a pull-up resistor for
microprocessor interfacing.
⎯
⎯
⎯
⎯
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.
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.
⎯ ⎯ ⎯ ⎯
When charging begins, CHRG is pulled low and remains
low for the duration of a normal charge cycle. When the
3559f
13
LTC3559
APPLICATIONS INFORMATION
NTC Thermistor
value of R25 or approximately 54k (for a Vishay “Curve
1” thermistor, this corresponds to approximately 40°C). If
the battery charger is in constant voltage mode, the safety
timer will pause until the thermistor indicates a return to
a valid temperature.
The battery temperature is measured by placing a nega-
tive temperature coefficient (NTC) thermistor close to the
battery pack. The NTC circuitry is shown in Figure 3.
To use this feature, connect the NTC thermistor, R
,
,
NTC
NOM
As the temperature drops, the resistance of the NTC
thermistor rises. The battery charger is also designed
to pause charging when the value of the NTC thermistor
increases to 3.25 times the value of R25. For a Vishay
“Curve 1” thermistor, this resistance, 325k, corresponds
to approximately 0°C. The hot and cold comparators each
haveapproximately3°Cofhysteresistopreventoscillation
about the trip point. Grounding the NTC pin disables all
NTC functionality.
betweentheNTCpinandground,andabiasresistor,R
from V to NTC. R
should be a 1% resistor with a
CC
NOM
value equal to the value of the chosen NTC thermistor at
25°C (R25). A 100k thermistor is recommended since
thermistor current is not measured by the battery charger
and its current will have to be considered for compliance
with USB specifications.
The battery charger will pause charging when the re-
sistance of the NTC thermistor drops to 0.54 times the
DUVLO, UVLO AND SUSPEND
IF SUSP < 0.4V AND
DISABLE MODE
NO
POWER
CHRG HIGH IMPEDANCE
ON
V
CC
V
CC
> 4V AND
> BAT + 130mV
YES
FAULT
NTC FAULT
STANDBY MODE
BATTERY CHARGING SUSPENDED
CHRG PULSES
NO CHARGE CURRENT
CHRG HIGH IMPEDANCE
NO FAULT
BAT ≤ 2.9V
2.9V < BAT < 4.1V
BAT > 2.9V
TRICKLE CHARGE MODE
CONSTANT CURRENT MODE
4-HOUR
TIMEOUT
1/10 FULL CHARGE CURRENT
CHRG STRONG PULL-DOWN
30 MINUTE TIMER BEGINS
FULL CHARGE CURRENT
CHRG STRONG PULL-DOWN
30 MINUTE
TIMEOUT
DEFECTIVE BATTERY
CONSTANT VOLTAGE MODE
NO CHARGE CURRENT
CHRG PULSES
4-HOUR TERMINATION TIMER
BEGINS
BAT DROPS BELOW 4.1V
4-HOUR TERMINATION TIMER RESETS
3559 F02
Figure 2. State Diagram of the Battery Charger Operation
3559f
14
LTC3559
APPLICATIONS INFORMATION
Alternate NTC Thermistors and Biasing
In the explanation below, the following notation is used.
R25 = Value of the thermistor at 25°C
The battery charger provides temperature qualified
charging if a grounded thermistor and a bias resistor are
connected to the NTC pin. 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).
R
R
= Value of thermistor at the cold trip point
NTC|COLD
= Value of the thermistor at the hot trip point
NTC|HOT
r
r
= Ratio of R
to R25
COLD
NTC|COLD
= Ratio of R
to R25
HOT
NTC|HOT
R
= Primary thermistor bias resistor (see Figure 3)
NOM
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.
R1 = Optional temperature range adjustment resistor (see
Figure 4)
The trip points for the battery charger’s temperature quali-
fication are internally programmed at 0.349 • V for the
CC
hot threshold and 0.765 • V for the cold threshold.
CC
Therefore, the hot trip point is set when:
RNTC|HOT
• VCC = 0.349 • VCC
RNOM +RNTC|HOT
and the cold trip point is set when:
NTC thermistors have temperature characteristics which
areindicatedonresistance-temperatureconversiontables.
TheVishay-DalethermistorNTHS0603N011-N1003F,used
in the following examples, has a nominal value of 100k
and follows the Vishay “Curve 1” resistance-temperature
characteristic.
RNTC|COLD
• VCC = 0.765 • VCC
RNOM +RNTC|COLD
V
NTC BLOCK
V
CC
CC
16
16
0.765 • V
CC
0.765 • V
CC
(NTC RISING)
(NTC RISING)
–
+
R
–
+
R
NOM
NOM
105k
100k
TOO_COLD
TOO_HOT
TOO_COLD
TOO_HOT
NTC
NTC
13
13
R1
12.7k
R
100k
NTC
–
+
–
+
R
100k
NTC
0.349 • V
0.349 • V
CC
(NTC FALLING)
CC
(NTC FALLING)
+
–
+
–
NTC_ENABLE
NTC_ENABLE
0.017 • V
CC
(NTC FALLING)
0.017 • V
CC
(NTC FALLING)
3559 F03
3559 F04
Figure 3. Typical NTC Thermistor Circuit
Figure 4. NTC Thermistor Circuit with Additional Bias Resistor
3559f
15
LTC3559
APPLICATIONS INFORMATION
Solving these equations for R
and R
NTC|COLD
NTC|HOT
For example, to set the trip points to 0°C and 45°C with
a Vishay Curve 1 thermistor choose:
results in the following:
R
= 0.536 • R
NTC|HOT
NOM
3.266 – 0.4368
RNOM
=
•100k = 104.2k
and
2.714
R
= 3.25 • R
NTC|COLD
NOM
the nearest 1% value is 105k.
By setting R
equal to R25, the above equations result
NOM
= 0.536 and r
R1 = 0.536 • 105k – 0.4368 • 100k = 12.6k
in r
= 3.25. Referencing these ratios
HOT
COLD
the nearest 1% value is 12.7k. The final solution is shown
in Figure 4 and results in an upper trip point of 45°C and
a lower trip point of 0°C.
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.
USB and Wall Adapter Power
By using a bias resistor, R
, different in value from
NOM
Although the battery charger is designed to draw power
from a USB port to charge Li-Ion batteries, a wall adapter
can also be used. Figure 5 shows an example of how to
combine wall adapter and USB power inputs. A P-channel
MOSFET, MP1, is used to prevent back conduction into
the USB port when a wall adapter is present and Schottky
diode, D1, is used to prevent USB power loss through the
1k pull-down resistor.
R25, the hot and cold trip points can be moved in either
direction.Thetemperaturespanwillchangesomewhatdue
to the nonlinear behavior of the thermistor. The following
equations can be used to easily calculate a new value for
the bias resistor:
rHOT
RNOM
RNOM
=
•R25
•R25
0.536
Typically, a wall adapter can supply significantly more
current than the 500mA-limited USB port. Therefore, an
N-channel MOSFET, MN1, and an extra program resistor
are used to increase the maximum charge current to
950mA when the wall adapter is present.
rCOLD
3.25
=
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.
5V WALL
I
BAT
ADAPTER
BAT
BATTERY
CHARGER
V
CC
950mA I
CHG
D1
USB
POWER
MP1
500mA I
+
CHG
Li-Ion
BATTERY
FromtheVishayCurve1R-Tcharacteristics,r is0.2488
at 60°C. Using the above equation, R
to 46.4k. With this value of R
about 16°C. Notice that the span is now 44°C rather than
the previous 40°C.
PROG
HOT
should be set
NOM
1.65k
MN1
, the cold trip point is
NOM
1.74k
1k
3559 F05
The upper and lower temperature trip points can be inde-
pendentlyprogrammedbyusinganadditionalbiasresistor
as shown in Figure 4. The following formulas can be used
Figure 5. Combining Wall Adapter and USB Power
to compute the values of R
and R1:
NOM
r
COLD –rHOT
RNOM
=
•R25
2.714
R1= 0.536 •RNOM –rHOT •R25
3559f
16
LTC3559
APPLICATIONS INFORMATION
Power Dissipation
Furthermore, the voltage at the PROG pin will change
proportionally with the charge current as discussed in
the Programming Charge Current section.
The conditions that cause the LTC3559 to reduce charge
current through thermal feedback can be approximated
by considering the power dissipated in the IC. For high
charge currents, the LTC3559 power dissipation is
approximately:
It is important to remember that LTC3559 applications do
notneedtobedesignedforworst-casethermalconditions
since the IC will automatically reduce power dissipation
when the junction temperature reaches approximately
105°C.
P = V – V
•I
BAT
(
)
D
CC
BAT
where P is the power dissipated, V is the input supply
D
CC
Battery Charger Stability Considerations
voltage, V is the battery voltage, and I is the charge
BAT
BAT
The LTC3559 battery charger contains two control loops:
the constant voltage and constant current loops. The con-
stantvoltageloopisstablewithoutanycompensationwhen
abatteryisconnectedwithlowimpedanceleads.Excessive
lead length, however, may add enough series inductance
to require a bypass capacitor of at least 1.5μF from BAT
to GND. Furthermore, a 4.7μF capacitor with a 0.2Ω to 1Ω
series resistor from BAT to GND is required to keep ripple
voltage low when the battery is disconnected.
current. It is not necessary to perform any worst-case
power dissipation scenarios because the LTC3559 will
automatically reduce the charge current to maintain the
die temperature at approximately 105°C. However, the
approximate ambient temperature at which the thermal
feedback begins to protect the IC is:
TA =105°C–PDθJA
T =105°C– V – V
•IBAT •θJA
(
)
A
CC
BAT
High value capacitors with very low ESR (especially
ceramic) reduce the constant voltage loop phase margin,
possibly resulting in instability. Ceramic capacitors up to
22μF may be used in parallel with a battery, but larger
ceramics should be decoupled with 0.2Ω to 1Ω of series
resistance.
Example: Consider an LTC3559 operating from a USB port
providing 500mA to a 3.5V Li-Ion battery. The ambient
temperatureabovewhichtheLTC3559willbegintoreduce
the 500mA charge current is approximately:
T =105°C– 5V –3.5V • 500mA •68°C / W
(
) (
)
A
In constant current mode, the PROG pin is in the feedback
loop,notthebattery.Becauseoftheadditionalpolecreated
bythePROGpincapacitance,capacitanceonthispinmust
be kept to a minimum. With no additional capacitance on
the PROG pin, the charger is stable with program resistor
valuesashighas25K. However, additionalcapacitanceon
this node reduces the maximum allowed program resis-
tor. The pole frequency at the PROG pin should be kept
above 100kHz. Therefore, if the PROG pin is loaded with a
TA =105°C–0.75W •68°C / W =105°C– 45°
TA = 54°C
The LTC3559 can be used above 70°C, but the charge cur-
rentwillbereducedfrom500mA. Theapproximatecurrent
at a given ambient temperature can be calculated:
105°C– TA
IBAT
=
V – V
•θ
(
)
CC
BAT
JA
capacitance,C
,thefollowingequationshouldbeused
PROG
Using the previous example with an ambient tem-
perature of 88°C, the charge current will be reduced to
approximately:
to calculate the maximum resistance value for R
:
PROG
1
RPROG
≤
2π •105 •CPROG
105°C–88°C
17°C
IBAT
=
=
5V –3.5V •68°C / W 90°C / A
(
)
IBAT =167mA
3559f
17
LTC3559
APPLICATIONS INFORMATION
the current from building up in the cable too fast thus
dampening out any resonant overshoot.
Average,ratherthaninstantaneous,batterycurrentmaybe
of interest to the user. For example, if a switching power
supply operating in low-current mode is connected in
parallel with the battery, the average current being pulled
out of the BAT pin is typically of more interest than the
instantaneous current pulses. In such a case, a simple RC
filter can be used on the PROG pin to measure the average
battery current as shown in Figure 6. A 10k resistor has
been added between the PROG pin and the filter capacitor
to ensure stability.
Buck Switching Regulator General Information
The LTC3559 contains two 2.25MHz constant-frequency
current mode switching regulators that provide up to
400mA each. Both switchers can be programmed for a
minimumoutputvoltageof0.8Vandcanbeusedtopower
a microcontroller core, microcontroller I/O, memory or
other logic circuitry. Both regulators support 100% duty
cycle operation (dropout mode) when the input voltage
dropsveryclosetotheoutputvoltageandarealsocapable
of operating in Burst Mode operation for highest efficien-
ciesatlightloads(BurstModeoperationispinselectable).
The switching regulators also include soft-start to limit
inrush current when powering on, short circuit current
protection, and switch node slew limiting circuitry to
reduce radiated EMI.
LTC3559
CHARGE
10k
CURRENT
PROG
MONITOR
GND
CIRCUITRY
R
C
FILTER
PROG
3559 F06
Figure 6. Isolated Capacitive Load on PROG Pin and Filtering
A single MODE pin sets both regulators in Burst Mode
operationorpulseskipoperatingmodewhileeachregula-
tor is enabled individually through their respective enable
USB Inrush limiting
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 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 damag-
ing the LTC3559 during a hot insertion, the soft connect
circuit in Figure 7 can be employed.
pinsEN1andEN2.Thebuckregulatorsinputsupply(PV )
IN
should be connected to the battery pin (BAT). This allows
the undervoltage lockout circuit on the BAT pin to disable
the buck regulators when the BAT voltage drops below
2.45V. Do not drive the buck switching regulators from
a voltage other than BAT. A 2.2μF decoupling capacitor
from the PV pin to GND is recommended.
IN
Buck Switching Regulator
Output Voltage Programming
In the circuit of Figure 7, capacitor C1 holds MP1 off when
thecableisfirstconnected.EventuallyC1beginstocharge
up to the USB voltage applying increasing gate support
to MP1. The long time constant of R1 and C1 prevents
Both switching regulators can be programmed for output
voltages greater than 0.8V. The output voltage for each
buck switching regulator is programmed using a resistor
divider from the switching regulator output connected to
the feedback pins (FB1 and FB2) such that:
MP1
Si2333
V
V
OUT
= 0.8(1 + R1/R2)
CC
C1
100nF
5V USB
INPUT
Typical values for R1 are in the range of 40k to 1M. The
capacitor CFB cancels the pole created by feedback re-
sistors and the input capacitance of the FB pin and also
helps to improve transient response for output voltages
much greater than 0.8V. A variety of capacitor sizes can
C2
10μF
LTC3559
USB CABLE
R1
40k
GND
3559 F07
Figure 7. USB Soft Connect Circuit
be used for CFB but a value of 10pF is recommended for
3559f
18
LTC3559
APPLICATIONS INFORMATION
most applications. Experimentation with capacitor sizes
between 2pF and 22pF may yield improved transient
response if so desired by the user.
regulators will automatically skip pulses as needed to
maintain output regulation. At high duty cycle (V
>
OUT
PV /2) in pulse skip mode, it is possible for the inductor
IN
current to reverse causing the buck converter to switch
continuously. Regulation and low noise operation are
maintained but the input supply current will increase to a
couple mA due to the continuous gate switching.
Buck Switching Regulator Operating Modes
The step-down switching regulators include two possible
operating modes to meet the noise/power needs of a
variety of applications.
During Burst Mode operation, the step-down switching
regulators automatically switch between fixed frequency
PWM operation and hysteretic control as a function of
the load current. At light loads the step-down switching
regulators control the inductor current directly and use a
hystereticcontrollooptominimizebothnoiseandswitching
losses. DuringBurstModeoperation, theoutputcapacitor
is charged to a voltage slightly higher than the regulation
point. The step-down switching regulator then goes into
sleep mode, during which the output capacitor provides
the load current. In sleep mode, most of the switching
regulator’s circuitry is powered down, helping conserve
battery power. When the output voltage drops below a
pre-determined value, the step-down switching regulator
circuitryispoweredonandanotherburstcyclebegins.The
sleeptimedecreasesastheloadcurrentincreases.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 skip 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.
In pulse skip mode, an internal latch is set at the start of
every cycle, which turns on the main P-channel MOSFET
switch.Duringeachcycle,acurrentcomparatorcompares
thepeakinductorcurrenttotheoutputofanerroramplifier.
The output of the current comparator resets the internal
latch,whichcausesthemainP-channelMOSFETswitchto
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 necessary compensation is
internal to the step-down switching regulator requiring
only a single ceramic output capacitor for stability. At
light loads in pulse skip mode, 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 or SW2) goes high impedance and the switch
node voltage will “ring”. This is discontinuous operation,
and is normal behavior for a switching regulator. At very
light loads in pulse skip mode, the step-down switching
Thestep-downswitchingregulatorsallowmodetransition
on-the-fly, providing seamless transition between modes
even under load. This allows the user to switch back and
forth between modes to reduce output ripple or increase
low current efficiency as needed. Burst Mode operation is
set by driving the MODE pin high, while pulse skip mode
is achieved by driving the MODE pin low.
P
VIN
EN
MP
SW
PWM
L
V
OUT
CONTROL
+
C
O
C
MODE
FB
MN
R1
R2
FB
0.8V
Buck Switching Regulator in Shutdown
The buck switching regulators are in shutdown when
not enabled for operation. In shutdown, all circuitry in
the buck switching regulator is disconnected from the
regulator input supply, leaving only a few nanoamps of
GND
3559 F08
Figure 8. Buck Converter Application Circuit
3559f
19
LTC3559
APPLICATIONS INFORMATION
leakage pulled to ground through a 10k resistor on the
switch (SW1 or SW2) pin when in shutdown.
Buck Switching Regulator Inductor Selection
The buck regulators are designed to work with inductors
in the range of 2.2μH to 10μH, but for most applications
a 4.7μH inductor is suggested. Larger value inductors
reduceripplecurrentwhichimprovesoutputripplevoltage.
Lowervalueinductorsresultinhigherripplecurrentwhich
improvestransientresponsetime. Tomaximizeefficiency,
choose an inductor with a low DC resistance. For a 1.2V
output efficiency is reduced about 2% for every 100mΩ
series resistance at 400mA load current, and about 2%
for every 300mΩ series resistance at 100mA load curent.
Choose an inductor with a DC current rating at least 1.5
timeslargerthanthemaximumloadcurrenttoensurethat
the inductor does not saturate during normal operation.
If output short circuit is a possible condition the induc-
tor should be rated to handle the maximum peak current
specified for the buck regulators.
Buck Switching Regulator Dropout Operation
It is possible for a step-down switching regulator’s input
voltagetoapproachitsprogrammedoutputvoltage(e.g.,a
battery voltage of 3.4V with a programmed output voltage
of 3.3V). When this happens, the PMOS switch duty cycle
increasesuntilitisturnedoncontinuouslyat100%.Inthis
dropoutcondition,therespectiveoutputvoltageequalsthe
regulator’s input voltage minus the voltage drops across
the internal P-channel MOSFET and the inductor.
Buck Switching Regulator Soft-Start Operation
Soft-start is accomplished by gradually increasing the
peak inductor current for each switching regulator over
a 500μs period. This allows each output to rise slowly,
helping minimize the battery in-rush current required to
charge up the regulator’s output capacitor. A soft-start
cycle occurs whenever a switcher first turns on, or after a
faultconditionhasoccurred(thermalshutdownorUVLO).
A soft-start cycle is not triggered by changing operating
modes using the MODE pin. This allows seamless output
operation when transitioning between operating modes.
Differentcorematerialsandshapeswillchangethesize/cur-
rentandprice/currentrelationshipofaninductor.Toroidor
shieldedpotcoresinferriteorpermalloymaterialsaresmall
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 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 buck regulator requires to operate.
Buck Switching Regulator
Switching Slew Rate Control
Thebuckswitchingregulatorscontaincircuitrytolimitthe
slewrateoftheswitchnode(SW1andSW2).Thiscircuitry
is designed to transition the switch node over a period of
a couple of nanoseconds, significantly reducing radiated
EMI and conducted supply noise while maintaining high
efficiency.
The inductor value also has an effect on Burst Mode
operation. Lower inductor values will cause Burst Mode
switching frequency to increase.
Table 2 shows several inductors that work well with the
LTC3559. These inductors offer a good compromise
in current rating, DCR and physical size. Consult each
manufacturer for detailed information on their entire
selection of inductors.
Buck Switching Regulator Low Supply Operation
An undervoltage lockout (UVLO) circuit on PV shuts
IN
down the step-down switching regulators when BAT
drops below about 2.5V. This UVLO prevents the step-
down switching regulators from operating at low supply
voltages where loss of regulation or other undesirable
operation may occur.
3559f
20
LTC3559
APPLICATIONS INFORMATION
Table 2 Recommended Inductors
INDUCTOR TYPE
L (μH)
MAX I (A)
MAX DCR(Ω)
SIZE IN MM (L × W × H)
MANUFACTURER
DC
DB318C
4.7
3.3
4.7
3.3
4.7
3.3
1.07
1.20
0.79
0.90
1.15
1.37
0.1
0.07
3.8 × 3.8 × 1.8
3.8 × 3.8 × 1.8
3.6 × 3.6 × 1.2
3.6 × 3.6 × 1.2
3.0 × 2.8 × 1.2
3.0 × 2.8 × 1.2
Toko
www.toko.com
D312C
0.24
0.20
0.13*
0.105*
DE2812C
CDRH3D16
CDRH2D11
4.7
3.3
4.7
3.3
4.7
0.9
1.1
0.11
0.085
0.17
4 × 4 × 1.8
4 × 4 × 1.8
3.2 × 3.2 × 1.2
3.2 × 3.2 × 1.2
4.9 × 4.9 × 1
Sumida
www.sumida.com
0.5
0.6
0.75
0.123
0.19
CLS4D09
SD3118
4.7
3.3
4.7
3.3
4.7
3.3
4.7
3.3
1.3
1.59
0.8
0.97
1.29
1.42
1.08
1.31
0.162
0.113
3.1 × 3.1 × 1.8
3.1 × 3.1 × 1.8
3.1 × 3.1 × 1.2
3.1 × 3.1 × 1.2
5.2 × 5.2 × 1.2
5.2 × 5.2 × 1.2
5.2 × 5.2 × 1.0
5.2 × 5.2 × 1.0
Cooper
www.cooperet.com
SD3112
SD12
0.246
0.165
0.117*
0.104*
0.153*
0.108*
SD10
LPS3015
4.7
3.3
1.1
1.3
0.2
0.13
3.0 × 3.0 × 1.5
3.0 × 3.0 × 1.5
Coilcraft
www.coilcraft.com
*Typical DCR
Buck Switching Regulator
Table 3: Recommended Ceramic Capacitor Manufacturers
Input/Output Capacitor Selection
AVX
Murata
(803) 448-9411
(714) 852-2001
(408) 537-4150
(888) 835-6646
www.avxcorp.com
www.murata.com
www.t-yuden.com
www.tdk.com
Low ESR (equivalent series resistance) ceramic capaci-
tors should be used at both switching regulator outputs
as well as the switching regulator input supply. Only
X5R or X7R ceramic capacitors should be used because
they retain their capacitance over wider voltage and
temperature ranges than other ceramic types. A 10μF
output capacitor 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. The switching
regulator input supply should be bypassed with a 2.2μF
capacitor. Consult manufacturer for detailed information
on their selection and specifications of ceramic capaci-
tors. Many manufacturers now offer very thin (< 1mm
tall) ceramic capacitors ideal for use in height-restricted
designs. Table3showsalistofseveralceramiccapacitor
manufacturers.
Taiyo Yuden
TDK
PCB Layout Considerations
As with all DC/DC regulators, careful attention must be
paid while laying out a printed circuit board (PCB) and to
componentplacement.Theinductors,inputPV capacitor
IN
and output capacitors must all be placed as close to the
LTC3559aspossibleandonthesamesideastheLTC3559.
All connections must be made on that same layer. Place
a local unbroken ground plane below these components
that is tied to the Exposed Pad (Pin 17) of the LTC3559.
The Exposed Pad must also be soldered to system ground
for proper operation.
3559f
21
LTC3559
TYPICAL APPLICATIONS
The Output Voltage of a Buck Regulator is Programmed for 3.3V. When BAT Voltage Approaches 3.3V, the Regulator Operates in
⎯
⎯
⎯
⎯
Dropout and the Output Voltage will be BAT – (ILOAD • 0.6). An LED at CHRG Gives a Visual Indication of the Battery Charger State. A
3-Resistor Bias Network for NTC Sets Hot and Cold Trip Points at Approximately 55°C and 0°C
UP TO
950mA
ADAPTER
4.5V TO 5.5V
V
BAT
CC
SINGLE
Li-lon CELL
2.7V TO 4.2V
+
1μF
510Ω 110k
PV
IN
NTC
2.2μF
28.7k
100k
NTC
NTH50603N01
LTC3559
4.7μH
1.02M
3.3V AT
400mA
CHRG
PROG
SUSP
HPWR
MODE
EN1
SW1
FB1
887Ω
22pF
22pF
10μF
324k
649k
4.7μH
1.8V AT
400mA
SW2
FB2
DIGITALLY
CONTROLLED
806k
10μF
EN2
GND EXPOSED PAD
3559 TA03
Buck Regulator Efficiency vs ILOAD
Buck Regulator Efficiency vs ILOAD
100
90
80
70
60
50
40
30
20
10
0
100
90
80
70
60
50
40
30
20
10
0
Burst Mode
OPERATION
Burst Mode
OPERATION
PULSE SKIP
MODE
PULSE SKIP
MODE
V
= 1.8V
OUT
PV = 4.2V
IN
OUT
PV = 2.7V
IN
PV = 4.2V
IN
V
= 3.3V
0.1
1
10
(mA)
100
1000
0.1
1
10
(mA)
100
1000
I
I
LOAD
LOAD
3559 TA02b
3559 TA02c
3559f
22
LTC3559
TYPICAL APPLICATIONS
The Battery Can be Charged with Up to 950mA of Charge Current. Buck Regulator 2 is Enabled Only After VOUT1 is Up to Approximately
0.7V. This Provides a Sequencing Function Which May be Desirable in Applications Where a Microprocessor Needs to be Powered Up
⎯
⎯
⎯
⎯
Before Peripherals. CHRG Interfaces to a Microprocessor Which Decodes the Battery Charger State
UP TO
950mA
ADAPTER
4.5V TO 5.5V
V
BAT
CC
SINGLE
Li-lon CELL
2.7V TO 4.2V
+
1μF
100k
PV
IN
NTC
2.2μF
100k
NTC
NTH50603NO1
100k
LTC3559
4.7μH
655k
2.5V AT
400mA
TO
CHRG
PROG
SUSP
HPWR
MODE
EN1
SW1
FB1
MICROPROCESSOR
887Ω
22pF
22pF
10μF
309k
649k
DIGITALLY
CONTROLLED
4.7μH
324k
1.2V AT
400mA
10μF
SW2
FB2
EN2
GND EXPOSED PAD
3559 TA02
PACKAGE DESCRIPTION
UD Package
16-Lead Plastic QFN (3mm × 3mm)
(Reference LTC DWG # 05-08-1691)
BOTTOM VIEW—EXPOSED PAD
PIN 1 NOTCH R = 0.20 TYP
OR 0.25 × 45° CHAMFER
R = 0.115
TYP
0.75 0.05
3.00 0.10
(4 SIDES)
15 16
0.70 0.05
PIN 1
TOP MARK
(NOTE 6)
0.40 0.10
1
1.45 0.05
2
1.45 0.10
(4-SIDES)
(4 SIDES)
3.50 0.05
2.10 0.05
PACKAGE
OUTLINE
(UD16) QFN 0904
0.200 REF
0.25 0.05
0.50 BSC
0.25 0.05
0.50 BSC
0.00 – 0.05
RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS
NOTE:
1. DRAWING CONFORMS TO JEDEC PACKAGE OUTLINE MO-220 VARIATION (WEED-2)
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
3559f
23
LTC3559
RELATED PARTS
PART NUMBER
DESCRIPTION
COMMENTS
LTC3550
Dual Input USB/AC Adapter Li-Ion Battery Charger with Synchronous Buck Converter, Efficiency: 93%, Adjustable Output at
Adjustable Output 600mA Buck Converter
600mA, Charge Current: 950mA Programmable, USB Compatible,
Automatic Input Power Detection and Selection
LTC3552
LTC3552-1
LTC3455
Standalone Linear Li-Ion Battery Charger with Adjustable Synchronous Buck Converter, Efficiency: >90%, Adjustable Outputs at
Output Dual Synchronous Buck Converter
800mA and 400mA, Charge Current Programmable up to 950mA, USB
Compatible, 5mm × 3mm DFN16 Package
Standalone Linear Li-Ion Battery Charger with Dual
Synchronous Buck Converter
Synchronous Buck Converter, Efficiency: >90%, Outputs 1.8V at 800mA
and 1.575 at 400mA, Charge Current Programmable up to 950mA, USB
Compatible
Dual DC/DC Converter with USB Power Manager and
Li-Ion Battery Charger
Seamless Transition Between Input Power Sources: Li-Ion Battery, USB
and 5V Wall Adapter, Two High Efficiency DC/DC Converters: Up to 96%,
Full-Featured Li-Ion Battery Charger with Accurate USB Current Limiting
(500mA/100mA) Pin Selectable Burst Mode® Operation, Hot SwapTM
Output for SDIO and Memory Cards, 4mm × 4mm QFN24 Package
LTC3456
2-Cell, Multi-Output DC/DC Converter with USB Power
Manager
Seamless Transition Between 2-Cell Battery, USB and AC Wall Adapter
Input Power Sources, Main Output: Fixed 3.3V Output, Core Output:
Adjustable from 0.8V to V
, Hot Swap Output for Memory Cards,
BATT(MIN)
Power Supply Sequencing: Main and Hot Swap Accurate USB Current
Limiting, High Frequency Operation: 1MHz, High Efficiency: Up to 92%,
4mm × 4mm QFN24 Package
LTC4080
500mA Standalone Charger with 300mA Synchronous
Buck
Charges Single Cell Li-Ion Batteries, Timer Termination +C/10, Thermal
Regulation, Buck Output: 0.8V to V , Buck Input V : 2.7V to 5.5V, 3mm
BAT
IN
× 3mm DFN10 Package
Burst Mode is a registered trademark of Linear Technology Corporation. Hot Swap is a trademark of Linear Technology Corporation.
3559f
LT 0507 • PRINTED IN USA
24 LinearTechnology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
●
●
© LINEAR TECHNOLOGY CORPORATION 2007
(408) 432-1900 FAX: (408) 434-0507 www.linear.com
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