LTC3499B_15 [Linear]
750mA Synchronous Step-Up DC/DC Converters with Reverse-Battery Protection;
| 型号： | LTC3499B_15 |
| 厂家： | 
Linear |
| 描述： | 750mA Synchronous Step-Up DC/DC Converters with Reverse-Battery Protection 电池 |
| 文件： | 总16页 (文件大小：251K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
LTC3499/LTC3499B
750mA Synchronous
Step-Up DC/DC Converters
with Reverse-Battery Protection
FEATURES
DESCRIPTION
TheLTC®3499/LTC3499Baresynchronous,fixedfrequency
step-up DC/DC power converters with integrated reverse
battery protection that protect and disconnect the devices
and load when the battery polarity is reversed while
delivering high efficiency in a small (3mm × 3mm) DFN
package. Trueoutputdisconnecteliminatesinrushcurrent
and allows zero load current in shutdown.
n
Reverse-Battery Protection for DC/DC Converter
and Load
n
High Efficiency: Up to 94%
n
Generates 5V at 175mA from a 1.8V Input
n
Operates from 1.8V to 5.5V Input Supply
n
2V to 6V Adjustable Output Voltage
n
Inrush Current Controlled During Start-Up
n
Output Disconnnect in Shutdown
The devices feature an input voltage range of 1.8V to 5.5V
enablingoperationfromtwoalkalineorNiMHbatteries.The
switching frequency is internally set at 1.2MHz allowing
the use of tiny surface mount inductors and capacitors.
A minimal number of external components are required
to generate output voltages ranging from 2V to 6V. The
LTC3499 features automatic Burst Mode operation to
increase efficiency at light loads, while the LTC3499B
features continuous switching at light loads.
n
Low Noise 1.2MHz PWM Operation
n
Tiny External Components
Automatic Burst Mode® Operation (LTC3499)
n
n
Continuous Switching at Light Loads (LTC3499B)
n
Overvoltage Protection
n
8-Lead (3mm × 3mm × 0.75mm) DFN
and MSOP Packages
APPLICATIONS
The soft-start time is externally programmable through a
small capacitor. Anti-ring circuitry reduces EMI emissions
by damping the inductor in discontinuous mode. The de-
vices feature <1µA shutdown supply current, integrated
overvoltage protection and are available in both 8-pin
(3mm × 3mm) DFN and 8-pin MSOP packages.
n
Medical Equipment
n
Digital Cameras
n
MP3 Players
Handheld Instruments
n
L, LT, LTC and LTM are registered trademarks of Linear Technology Corporation.
Burst Mode is a registered trademark of Linear Technology Corporation.
All other trademarks are the property of their respective owners.
TYPICAL APPLICATION
Two AA Cells to 5V Synchronous Boost Converter
Battery Current vs VIN
1.0
4.7µH
SHDN = 0V
V
IN
1.8V TO 3.2V
V
= 0V
OUT
+
V
IN
SW
OUT
FB
2.2µF
0.5
0
LTC3499
V
OUT
V
5V
ON OFF
SHDN
VC
175mA
1M
10µF
100k
330pF
SS
–0.5
–1.0
GND
324k
0.01µF
3499 TA01
–6
–4
–2
0
2
4
6
V
AND SW VOLTAGE (V)
IN
3499 TA01b
3499fc
1
LTC3499/LTC3499B
(Note 1)
ABSOLUTE MAXIMUM RATINGS
V to GND..................................................... – 7V to 7V
FB, SS to GND............................................. – 0.3V to 7V
Operating Temperature Range
IN
V
to GND .............................................. – 0.3V to 7V
OUT
SW to V
SW to GND
................................................... – 7V to 1V
(Notes 3, 4)......................................... –40°C to 85°C
Storage Temperature Range ................. –65°C to 125°C
Lead Temperature (Soldering, 10 sec)
OUT
DC............................................................... –7V to 7V
Pulsed < 100ns........................................... –7V to 8V
SHDN to GND................................................. – 7V to 7V
MSOP .............................................................. 300°C
PIN CONFIGURATION
TOP VIEW
TOP VIEW
SHDN
1
2
3
4
8
7
6
5
VC
FB
SHDN
1
2
3
4
8
7
6
5
VC
FB
V
IN
V
SW
9
IN
SW
V
OUT
V
OUT
GND
SS
GND
SS
MS8 PACKAGE
8-LEAD PLASTIC MSOP
= 125°C, θ = 160°C/W
DD PACKAGE
8-LEAD (3mm × 3mm) PLASTIC DFN
T
JMAX
JA
T
= 125°C, θ = 45°C
JA
JMAX
EXPOSED PAD (PIN 9) IS GND, MUST BE SOLDERED TO PCB
ORDER INFORMATION
LEAD FREE FINISH
LTC3499EDD#PBF
LTC3499BEDD#PBF
LTC3499EMS8#PBF
LTC3499BEMS8#PBF
TAPE AND REEL
PART MARKING
LBRB
PACKAGE DESCRIPTION
TEMPERATURE RANGE
–40°C to 85°C
LTC3499EDD#TRPBF
LTC3499BEDD#TRPBF
LTC3499EMS8#TRPBF
LTC3499BEMS8#TRPBF
8-Lead (3mm × 3mm) Plastic DFN
8-Lead (3mm × 3mm) Plastic DFN
8-Lead Plastic MSOP
LCDZ
–40°C to 85°C
LTBRC
–40°C to 85°C
LTCFB
8-Lead Plastic MSOP
–40°C to 85°C
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/
ELECTRICAL CHARACTERISTICS The l denotes specifications that apply over the full operating temperature
range, otherwise specifications are at TA = 25°C. VIN = 2.4V, VOUT = 5V, SHDN = 2.4V, TA = TJ unless otherwise noted. (Note 3)
SYMBOL
Supply
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
l
l
l
V
V
V
Minimum Start-Up Voltage
Output Voltage Adjust Range
FB Voltage
1.6
1.8
6
V
V
V
IN
2
OUT
FB
1.195
1.220
1.245
3499fc
2
LTC3499/LTC3499B
ELECTRICAL CHARACTERISTICS The l denotes specifications that apply over the full operating temperature
range, otherwise specifications are at TA = 25°C. VIN = 2.4V, VOUT = 5V, SHDN = 2.4V, TA = TJ unless otherwise noted. (Note 3)
SYMBOL
PARAMETER
CONDITIONS
V = 1.22V
FB
MIN
TYP
3
MAX
50
UNITS
nA
I
I
I
I
FB Input Current
FB
l
V
V
Quiescent Current
No Output Load
SHDN = 0V, V
300
0.1
600
1
µA
VIN
IN
IN
Quiescent Current in Shutdown
= 0V
OUT
µA
SD
Quiescent Current – Burst Mode Operation
V
V
Current at 2.4V (LTC3499 Only)
OUT
20
1.5
µA
µA
BURST
IN
Current at 5V (LTC3499 Only)
I
I
NMOS Switch Leakage Current
PMOS Switch Leakage Current
NMOS Switch On Resistance
V
V
= 6V
0.1
0.1
5
5
µA
µA
NMOS
SW
= 6V, V = 0V
PMOS
OUT
SW
R
V
V
= 3.3V
= 5V
0.45
0.4
Ω
Ω
NMOS
PMOS
OUT
OUT
R
PMOS Switch On Resistance
V
V
= 3.3V
= 5V
0.58
0.45
Ω
Ω
OUT
OUT
l
I
t
NMOS Current Limit
0.75
80
1
1
A
ns
LIM
Current Limit Delay to Output
Maximum Duty Cycle
Note 2
60
85
DLY, ILIM
l
l
l
D
D
%
MAX
Minimum Duty Cycle
0
%
MIN
f
Frequency Accuracy
1.2
40
–5
5
1.4
MHz
µmhos
µA
OSC
G
Error Amplifier Transconductance
Error Amplifier Source Current
Error Amplifier Sink Current
SS Current Source
mEA
SOURCE
SINK
I
I
I
µA
V
= 1V
SS
–3
6.8
400
µA
SS
V
V
V
V
Overvoltage Threshold
Overvoltage Hysteresis
V
OV
OUT
OUT
mV
OV(HYST)
Shutdown
l
l
V
SHDN Input Low Voltage
SHDN Input High Voltage
SHDN Input Current
0.2
1
V
V
SHDN(LOW)
SHDN(HIGH)
V
Measured at SW
1.2
I
SD
µA
Reverse Battery
l
l
l
I
I
I
V
V
Reverse-Battery Current
V
OUT
V
OUT
V
OUT
= 0V, V = V
= V = –6V
5
µA
µA
µA
VOUT,REVBATT
VIN,REVBATT
SHDN,REVBATT
OUT
IN
SHDN
SHDN
SHDN
SW
and V Reverse-Battery Current
= 0V, V = V
= V = –6V
–5
–5
IN
SW
IN
SW
SHDN Reverse-Battery Current
= 0V, V = V
= V = –6V
SW
IN
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 4: These ICs include overtemperature protection that is intended
to protect the devices during momentary overload conditions. Junction
temperatures will exceed 125°C when overtemperature protection is
active. Continuous operation above the specified maximum operating
temperature range may impair device reliability.
Note 2: Specification is guaranteed by design and not 100% tested in
production.
Note 3:The LTC3499E/LTC3499BE are guaranteed to meet device
specifications from 0°C to 85°C. Specifications over the –40°C to 85°C
operating temperature are assured by design, characterization and
correlation with statistical process controls.
3499fc
3
LTC3499/LTC3499B
TYPICAL PERFORMANCE CHARACTERISTICS TA = 25°C, unless otherwise noted.
2-Cell to 5V Efficiency
vs Load Current (LTC3499 Only)
Li-Ion to 5V Efficiency
vs Load Current (LTC3499 Only)
2-Cell to 5V Efficiency
vs Load Current (LTC3499B Only)
100
90
80
70
60
50
40
30
20
10
0
100
90
100000
10000
100
90
100000
10000
1000
100
EFFICIENCY
EFFICIENCY
80
80
70
1000
100
70
60
50
40
30
POWER LOSS
POWER LOSS
60
50
40
10
1
10
V
V
V
= 3.2V
= 2.4V
= 1.8V
V
V
V
= 4.2V
= 3.6V
= 3V
V
V
V
= 3.2V
= 2.4V
= 1.8V
IN
IN
IN
IN
IN
IN
1
IN
IN
IN
0.1
0.1
0.1
1
10
100
1000
0.1
1
10
100
1000
1
10
LOAD CURRENT (mA)
1000
0.1
100
LOAD CURRENT (mA)
LOAD CURRENT (mA)
3499 G17
3499 G01
3499 G03
Burst Mode Output Current
Threshold vs Input Voltage
(LTC3499 Only)
Current Limit Accuracy
vs Temperature
2-Cell to 3.3V Efficiency
vs Load Current (LTC3499 Only)
1.04
1.03
1.02
60
50
40
30
20
10
0
100
90
100000
V
= 5V
OUT
10000
EFFICIENCY
80
70
1000
100
1.01
1.00
0.99
0.98
0.97
0.96
60
50
40
10
1
POWER LOSS
V
V
V
= 3V
= 2.4V
= 1.8V
IN
IN
IN
0.1
–25
0
50
1.8
2.8
3.3
3.8
4.3
4.8
–50
75
100
25
2.3
0.1
1
10
100
1000
INPUT VOLTAGE (V)
TEMPERATURE (°C)
LOAD CURRENT (mA)
3499 G04
3499 G05
3499 G02
Maximum Output Current
Capability vs VIN
No Load Input Current vs VIN
(LTC3499 Only)
Burst Mode Quiescent Current
vs Temperature (LTC3499 Only)
200
180
160
140
120
100
80
30
25
20
15
10
5
800
700
600
500
400
300
200
100
0
V
IN
> V
OUT
V
> V
OUT
IN
V
= 3.3V
OUT
V
= 3.3V
OUT
V
= 5V
OUT
V
= 5V
OUT
60
40
20
0
0
1.5
2.5
3.5
(V)
4.5
5.5
–50
0
25
50
75
100
3.5
(V)
–25
1.5
2.5
4.5
5.5
V
TEMPERATURE (°C)
V
IN
IN
3499 G07
3499 G08
3499 G06
3499fc
4
LTC3499/LTC3499B
TYPICAL PERFORMANCE CHARACTERISTICS TA = 25°C, unless otherwise noted.
Burst Mode Quiescent Current
vs Temperature
VIN and SW Reverse-Battery
FB Voltage vs Temperature
Current vs VIN and SW Voltage
1.0
0.5
30
25
20
15
10
5
1.2225
1.2220
1.2215
1.2210
1.2205
1.2200
1.2195
1.2190
1.2185
SHDN = 0V
V
OUT
= 0V
0
–0.5
–1.0
0
–25
0
50
–50
75
100
25
–50
0
25
50
75
100
–25
–6
–4
–2
0
2
4
6
TEMPERATURE (°C)
V
IN
AND SW VOLTAGE (V)
TEMPERATURE (°C)
3499 G09
3499 G08
3499 G11
Burst Mode Operation
(LTC3499 Only)
Fixed Frequency Discontinous
Mode Operation
Load Transient 50mA to 200mA
SW
2V/DIV
V
OUT
V
OUT
200mV/DIV
50mV/DIV
200mA
50mA
I
I
LOAD
L
I
100mA/DIV
100mA/DIV
L
50mA/DIV
3499 G12
3499 G13
3499 G14
V
V
= 2.4V
= 5V
20µs/DIV
V
V
= 2.4V
= 5V
200µs/DIV
V
V
= 2.4V
= 5V
OUT
200ns/DIV
IN
OUT
L = 4.7µH
IN
OUT
IN
I
= 50mA to 200mA
L = 4.7µH
LOAD
C
C
V
= 10µF
R
C
= 100k
= 680pF
= 10µF
OUT
Z
= 10pF (FEEDFORWARD CAPACITOR FROM
TO FB)
FF
OUT
F
OUT
L = 4.7µH
C
Soft-Start into 25Ω Load
Fixed Frequency Operation
V
IN
2V/DIV
SS
2V/DIV
SW
2V/DIV
V
OUT
I
L
2V/DIV
100mA/DIV
I
L
200mA/DIV
3499 G16
3499G15
V
V
= 2.4V
= 5V
200ns/DIV
V
V
= 2.4V
= 5V
1ms/DIV
IN
OUT
L = 4.7µH
IN
OUT
L = 4.7µH
C
C
= 0.01µF
SS
= 10µF
OUT
3499fc
5
LTC3499/LTC3499B
PIN FUNCTIONS
SHDN(Pin1):ShutdownInputforIC. Connecttoavoltage
greater than 1.2V to enable and a voltage less than 0.2V
to disable the LTC3499/LTC3499B.
SS (Pin 5): Soft-Start Input. Connect a capacitor from
SS to ground to control the inrush current at start-up.
An internal 3µA current source charges this pin. SS will
be discharged if SHDN is pulled low, thermal shutdown
V
(Pin 2): Input Supply Voltage. The valid operating
IN
occurs or V is below the minimum operating voltage.
IN
voltage is between 1.8V to 5.5V. V has reverse battery
IN
protection. Since the LTC3499/LTC3499B use V as the
V
(Pin 6): Power Supply Output. Connect a low ESR
IN
OUT
main bias source, bypass with a low ESR ceramic capaci-
output filter capacitor from this pin to the ground plane.
tor of at least 2.2µF.
FB (Pin 7): FB Input to Error Amplifier. Connect a resistor
SW (Pin 3): Switch Pin. Connect an inductor from V to
divider tap from V
to this pin to set the output voltage.
IN
OUT
this pin with a value between 2.2µH and 10µH. Keep PCB
trace lengths as short and wide as possible to minimize
EMI and voltage overshoot. If the inductor current falls to
zero or SHDN is low an internal 250Ω antiringing switch
The output voltage can be adjusted between 2V and 6V.
Referring to the Functional Block Diagram, the output
voltage is given by:
R1
R2
is connected from V to SW to minimize EMI.
IN
VOUT =1.22• 1+
GND (Pin 4/Exposed Pad, DD Package Pin 9): Signal
and Power Ground. The DD package exposed pad must
be soldered to the PCB power ground plane for electrical
connection and rated thermal performance.
VC (Pin 8): Error Amplifier Output. A frequency com-
pensation network is connected from this pin to GND to
compensate the boost converter loop. See Closing the
Feedthrough Loop section for guidelines.
3499fc
6
LTC3499/LTC3499B
FUNCTIONAL BLOCK DIAGRAM
C
IN
+
V
IN
1.8V TO 5.5V
L
2
3
V
SW
IN
REVERSE-BATTERY COMPARATOR
ANTI-RING
250Ω
+
1 = CLOSED
1 = CLOSED
0.7V
–
–
–
+
+
V
SELECT
OV COMPARATOR
V
OUT
6
7
V
OUT
+
–
1 = OFF
ERROR AMPLIFIER
C
FF
(OPTIONAL)
1.22V
+
–
R1
R2
6.8V
ENABLE
FB
PWM
C
OUT
THERMAL SD
SLEEP
LOGIC
AND
DRIVERS
VC
I
ZERO
8
5
C
C1
C
C2
RZ
1.2MHz
OSCILLATOR
SLOPE
COMPENSATION
Σ
3µA
SS
5k
+
–
C
SS
PWM COMPARATOR
ENABLE
TSD
Burst Mode
CONTROL
(LTC3499 ONLY)
+
–
SLEEP
CURRENT LIMIT COMPARATOR
REFERENCE
1A
TYP
–
SHDN
1
BIAS
ENABLE
UVLO
+
0.8V
SD
GND
4
3499 F01
Figure 1: Functional Block Diagram
3499fc
7
LTC3499/LTC3499B
OPERATION
TheLTC3499/LTC3499Bprovidehighefficiency, lownoise
power for boost applications with output voltages up to
6V. Operation can be best understood by referring to
the Functional Block Diagram in Figure 1. The synchro-
nous boost converters are housed in either an 8-lead
(3mm × 3mm) DFN or MSOP package and operates at a
In the event of an external shutdown or thermal shutdown
(TSD), C is discharged through a nominal 5kΩ imped-
SS
ance to GND. Once the condition is removed and SS is
discharged near ground, a soft-start will automatically
be re-initiated.
Error Amplifier
fixed 1.2MHz. With a 1.6V typical minimum V voltage
IN
these devices are well suited for applications using two
or three alkaline or nickel-metal hydride (NiMH) cells or
one Lithium-Ion (Li-Ion) cell. The LTC3499/LTC3499B
have integrated circuitry which protects the battery, IC,
and circuitry powered by the device in the event that the
input batteries are connected backwards (reverse battery
protection). The true output disconnect feature eliminates
A transconductance amplifier generates an error voltage
from the difference between the positive input internally
connected to the 1.22V reference and the negative input
connectedtoFB.Asimplecompensationnetworkisplaced
fromVCtoground. Internalclampslimittheminimumand
maximumerroramplifieroutputvoltageforimprovedlarge
signal transient response. A voltage divider from V
to
OUT
inrush current and allows V
to be zero volts during
OUT
GND programs the output voltage via FB from 2V to 6V
and is defined by the following equation:
shutdown. The current mode architecture simplifies loop
compensation with excellent load transient response.
R1
R2
The low R
, low gate charge synchronous switches
DS(ON)
VOUT =1.22• 1+
eliminate the need for an external Schottky diode recti-
fier, and provide efficient high frequency pulse width
modulation (PWM). Burst Mode quiescent current to the
Current Sensing
LTC3499 is only 20µA from V , maximizing battery life.
IN
Lossless current sensing converts the peak current signal
into a voltage which is summed with the internal slope
compensation. This summed signal is compared to the
error amplifier output to provide a peak current control
command for the PWM. Peak switch current is limited
to 750mA minimum.
The LTC3499B does not have Burst Mode operation and
thedevicecontinuesswitchingatconstantfrequency.This
results in the absence of low frequency output ripple at
the expense of light load efficiency.
LOW NOISE FIXED FREQUENCY OPERATION
Shutdown
Antiringing Control
The antiringing control connects a resistor across the
inductor to damp the ringing on SW in discontinuous
conduction mode. The LC resonant ringing (L = inductor,
The LTC3499/LTC3499B are shut down by pulling SHDN
below 0.2V, and activated by pulling the pin above 1.2V.
SHDN can be driven above V or V
as long as it is
IN
OUT
C
= capacitance on SW) is low energy, but can cause
SW
limited to less than the absolute maximum rating.
EMI radiation if antiringing control is not present.
Soft-Start
Zero Current Comparator
Thesoft-starttimeisprogrammedwithanexternalcapaci-
tor to ground on SS. An internal current source charges
Thezerocurrentcomparatormonitorstheinductorcurrent
to the output and shuts off the synchronous rectifier once
this current reduces to approximately 40mA, preventing
negative inductor current.
the capacitor, C , with a nominal 3µA. The voltage on SS
SS
is used to clamp the voltage on VC. The soft-start time
is given by
t
= C (µF) • 200
SS
(msec)
3499fc
8
LTC3499/LTC3499B
OPERATION
Reverse-Battery Protection
capacitor will recharge causing the LTC3499 to re-enter
sleep if the output load current remains less than the
sleep threshold. The frequency of this intermittent PWM
(or burst) operation is proportional to load current.
Therefore, as the load current drops further below the
burst threshold, the LTC3499 operates in PWM mode
less frequently. When the load current increases above
the burst threshold, the LC3499 will resume continuous
PWM operation seamlessly.
Connectingthebatterybackwardsposesasevereproblem
to most power converters. At a minimum the battery will
bequicklydischarged.AlmostallICshaveaninherentdiode
from V (cathode) to ground (anode) which conducts ap-
IN
preciable current when V drops more than 0.7V below
IN
ground. Under this condition the integrated circuit will
most likely be damaged due to the excessive current draw.
There exists the possibility for the battery and circuitry
powered by the device to also be damaged. The LTC3499/
LTC3499Bhaveintegratedcircuitrywhichallowsnegligible
current flow under a reverse-battery condition, protecting
the battery, device and circuitry attached to the output. A
graph of the reverse-battery current drawn is shown in
the Typical Performance Characteristics.
Referring to the Functional Block Diagram, an optional
capacitor,C ,betweenV andFBinsomecircumstances
FF
OUT
can reduce peak-to-peak V
ripple and input quiescent
OUT
current during Burst Mode operation. Typical values for
C range from 10pF to 220pF.
FF
Output Disconnect and Inrush Current Limiting
Discrete methods of reverse battery protection put ad-
ditional dissipative elements in the high current path
reducing efficiency while increasing component count
to implement protection. The LTC3499/LTC3499B do not
suffer from either of these drawbacks.
The LTC3499/LTC3499B are designed to allow true output
disconnect by eliminating body diode conduction of the
internal P-channel MOSFET switch. This allows V
to
OUT
go to zero volts during shutdown without drawing any
current from the input source. It also provides for inrush
current limiting at turn-on, minimizing surge current seen
by the input supply.
Burst Mode Operation (LTC3499 only)
Portable devices frequently spend extended time in low
power or stand-by mode, only drawing high power when
specificfunctionsareenabled. Inordertoimprovebattery
life in these types of products, high power converter ef-
ficiency needs to be maintained over a wide output power
range. In addition to its high efficiency at moderate and
heavy loads, the LTC3499 includes automatic Burst Mode
operation that improves efficiency of the power converter
at light loads. Burst Mode operation is initiated if the
output load current falls below an internally programmed
threshold (see Typical Performance graph, Output Load
V > V
Operation
IN
OUT
The LTC3499/LTC3499B will maintain voltage regulation
when the input voltage is above the output voltage. This is
achievedbyterminatingtheswitchingonthesynchronous
P-channelMOSFETandapplyingV staticallyonthegate.
IN
This will ensure the volts • seconds of the inductor will
reverse during the time current is flowing to the output.
Since this mode will dissipate more power in the IC, the
maximum output current is limited in order to maintain
an acceptable junction temperature:
Burst Mode Threshold vs V ). Once initiated the Burst
IN
Mode operation circuitry shuts down most of the circuitry
in the LTC3499, keeping alive only the circuitry required
to monitor the output voltage.
125– TA
IOUT(MAX)
≅
θJA • V +1.5 – V
(
)
(
)
JA
IN
OUT
where T = ambient temperature and θ is the package
thermal resistance (45°C/W for the DD8 and 160°C/W
This state is referred to as sleep. In sleep, the LTC3499
only draws 20µA from the input supply, greatly enhancing
efficiency. When the output has drooped approximately
1% from its nominal regulation point, the LTC3499 wakes
up and commences normal PWM operation. The output
A
for the MS8).
For example at V = 4.5V, V
= 3.3V and T = 85°C in
A
IN
OUT
the DD8 package, the maximum output current is 330mA.
3499fc
9
LTC3499/LTC3499B
APPLICATIONS INFORMATION
PCB LAYOUT GUIDELINES
The inductor current ripple is typically set to 20% to 40%
of the maximum inductor current. For high efficiency,
choose an inductor with high frequency core material,
such as ferrite, to reduce core losses. The inductor should
have low ESR (equivalent series resistance) to reduce the
The high speed operation of the LTC3499/LTC3499B
demand careful attention to board layout. Advertised per-
formancewillnotbeachievedwithcarelesslayout.Figure 2
shows the recommended component placement. A large
copper area will help to lower the chip temperature. Traces
2
I R power losses, and must be able to handle the peak
inductor current without saturating. To minimize radiated
noise, use a toroidal or shielded inductor. See Table 1 for
some suggested inductor suppliers.
carrying high current (SW, V , GND) are kept short.
OUT
The lead length to the battery should be kept as short as
possible. The V and V
ceramic capacitors should be
IN
OUT
placed as close to the IC pins as possible.
Table 1. Inductor Vendor Information
PART NUMBER
SUPPLIER
WEB SITE
C
C2
EXPOSED PAD FOR DD8
MSS5131 and
Coilcraft
www.coilcraft.com
MOS6020 Series
C
C1
RZ
R2
VC
SLF7028 and
SLF7045 Series
TDK
www.component.tdk.com
1
2
3
4
8
7
6
5
SHDN
LQH55D Series
Murata
Sumida
Toko
www.murata.com
www.sumida.com
www.tokoam.com
V
IN
FB
V
CDRH4D28 Series
9
R1
C
C
L
+
IN
D53LC and
D62CB Series
V
BATT
OUT
SW
DT0703 Series
CoEV
FDK
www.coev.net
www.fdk.com
SS
MJPF2520 Series
OUT
GND
C
SS
Output Capacitor Selection
3499 F02
The output voltage ripple has three components to it. The
bulk value of the capacitor is set to reduce the ripple due
to charge into the capacitor each cycle. The maximum
ripple voltage due to charge is given by:
Figure 2: Recommended Component Placement
COMPONENT SELECTION
Inductor Selection
VIN
VRBULK =IP •
C
OUT • VOUT • f
(
)
The LTC3499/LTC3499B allow the use of small surface
mountinductorsandchipinductorsduetothefast1.2MHz
switching frequency. A minimum inductance value of
2.2µH is required. Larger values of inductance will allow
greater output current capability by reducing the induc-
tor ripple current. Increasing the inductance above 10µH
will increase total solution area while providing minimal
improvement in output current capability.
where I = peak inductor current and f = switching
P
frequency.
The ESR (equivalent series resistance) is usually the most
dominant factor for ripple in most power converters. The
ripple due to capacitor ESR is simply given by:
V
= I • C
P ESR
RCESR
where C
= capacitor equivalent series resistance.
ESR
3499fc
10
LTC3499/LTC3499B
APPLICATIONS INFORMATION
TheESL(equivalentseriesinductance)isalsoanimportant
factor for high frequency converters. Using small surface
mount ceramic capacitors, placed as close as possible to
into a copper plane with as much area as possible. If the
junction temperature continues to rise, the part will go
into thermal shutdown where switching will stop until the
temperature drops.
V
, will minimize ESL.
OUT
Low ESR capacitors should be used to minimize output
voltage ripple. A 4.7µF to 10µF output capacitor is suf-
ficientformostapplicationsandshouldbeplacedasclose
Closing the Feedback Loop
The LTC3499/LTC3499B utilize current mode control,
with internal slope compensation. Current mode control
eliminates the 2nd order filter due to the inductor and out-
put capacitor exhibited in voltage mode controllers, thus
simplifying it to a single pole filter response. The product
of the modulator control to output DC gain and the error
amp open loop gain gives the DC gain of the system:
to V
as possible. Larger values may be used to obtain
OUT
even lower output ripple and improve transient response.
X5R and X7R dielectric materials are preferred for their
ability to maintain capacitance over wide voltage and
temperature ranges.
Input Capacitor Selection
V
REF
G
G
G
= G
• G
•
DC
CONTROL
EA
The input filter capacitor reduces peak currents drawn
from the input source and reduces input switching noise.
Ceramiccapacitorsareagoodchoiceforinputdecoupling
duetotheirlowESRandabilitytowithstandreversevoltage
(i.e. non-polar nature). The capacitor should be located
as close as possible to the device. In most applications a
2.2µF input capacitor is sufficient. Larger values may be
used without limitations. Table 2 shows a list of several
ceramic capacitor manufacturers.
V
• G
CURRENT _ SENSE
OUT
V
IN
= 2 •
,
CONTROL
I
OUT
1
≈ 1000, G
=
CURRENT _ SENSE
EA
R
DS ON
(
)
The output filter pole is given by:
IOUT
π • VOUT •COUT
fFILTER _POLE
=
Table 2. Capacitor Vendor Information
(
)
SUPPLIER
AVX
WEB SITE
www.avxcorp.com
www.murata.com
www.component.tdk.com
www.t-yuden.com
where C
is the output filter capacitor.
OUT
Murata
TDK
The output filter zero is given by:
Taiyo Yuden
1
fFILTER _ ZERO
=
2• π •RESR •COUT
(
)
Thermal Considerations
where R
is the capacitor equivalent series resistance.
ESR
For the LTC3499/LTC3499B to deliver full output power, it
is imperative that a good thermal path be provided to dis-
sipate the heat generated within the package. For the DFN
package, this can be accomplished by taking advantage
of the large thermal pad on the underside of the device.
It is recommended that multiple vias in the printed circuit
board be used to conduct heat away from the part and
A troublesome feature of the boost regulator topology is
the right half plane (RHP) zero, given by:
2
VIN
fRHPZ
=
2• π •IOUT • VOUT •L
(
)
3499fc
11
LTC3499/LTC3499B
APPLICATIONS INFORMATION
V
There is a resultant gain increase with a phase lag which
makes it difficult to compensate the loop. At heavy loads
the right half plane zero can occur at a relatively low
frequency. The loop gain is typically rolled off before the
RHP zero frequency.
OUT
6
ERROR AMPLIFIER
R1
R2
1.22V
+
–
FB
7
The typical error amp compensation is shown in Figure 3,
following the equations for the loop dynamics:
VC
8
1
fPOLE1
~
R
Z
C
2• π •10e6 •C
C2
(
)
C1
C
C1
3499 F03
which is extremely close to DC.
1
Figure 3: Typical Error Amplifier Compensation
fZERO1
=
=
2• π •R •C
(
)
Z
C1
1
fPOLE2
2• π •R •C
(
)
Z
C2
3499fc
12
LTC3499/LTC3499B
TYPICAL APPLICATIONS
Lithium-Ion to 5V, 350mA
Lithium-Ion to 5V Efficiency
100
90
100000
L
4.7µH
10000
V
IN
C
EFFICIENCY
+
IN
Li-Ion
2.2µF
V
IN
SW
OUT
FB
80
3.1V TO 4.2V
1000
×5R
LTC3499
70
60
50
40
30
V
OUT
V
POWER LOSS
100
5V
ON OFF
SHDN
VC
350mA
1M
C
OUT
10
10µF
100k
×5R
SS
GND
V
V
V
= 4.2V
= 3.6V
= 3V
324k
IN
IN
IN
1
330pF
0.01µF
0.1
C
C
: TAIYO YUDEN X5R JMK212BJ225MD
IN
OUT
1
10
LOAD CURRENT (mA)
1000
0.1
100
: TAIYO YUDEN X5R JMK212BJ106MD
3499 F04a
L: COILCRAFT MSS5131-472MLB
3499 G03
Two Cells to 5V, 175mA
Two Cells to 5V Efficiency
100
90
100000
10000
L
4.7µH
V
IN
C
+
IN
EFFICIENCY
2 AA CELLS
2.2µF
V
IN
SW
OUT
FB
80
70
1000
100
1.8V TO 3.2V
×5R
LTC3499
V
OUT
V
5V
ON OFF
SHDN
VC
175mA
POWER LOSS
1M
C
60
50
40
10
1
OUT
10µF
100k
×5R
SS
V
V
V
= 3.2V
= 2.4V
= 1.8V
IN
IN
IN
GND
324k
330pF
0.01µF
0.1
0.1
1
10
100
1000
C
C
: TAIYO YUDEN X5R JMK212BJ225MD
IN
OUT
: TAIYO YUDEN X5R JMK212BJ106MD
LOAD CURRENT (mA)
3499 F05a
L: COILCRAFT MSS5131-472MLB
3499 G01
3499fc
13
LTC3499/LTC3499B
PACKAGE DESCRIPTION
DD Package
8-Lead Plastic DFN (3mm × 3mm)
(Reference LTC DWG # 05-08-1698 Rev C)
R = 0.125
0.40 0.10
TYP
5
8
0.70 0.05
3.5 0.05
2.10 0.05 (2 SIDES)
1.65 0.05
3.00 0.10
(4 SIDES)
1.65 0.10
(2 SIDES)
PIN 1
TOP MARK
(NOTE 6)
PACKAGE
OUTLINE
(DD8) DFN 0509 REV C
4
1
0.25 0.05
0.75 0.05
0.200 REF
0.25 0.05
0.50 BSC
0.50
BSC
2.38 0.10
2.38 0.05
BOTTOM VIEW—EXPOSED PAD
0.00 – 0.05
RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS
APPLY SOLDER MASK TO AREAS THAT ARE NOT SOLDERED
NOTE:
1. DRAWING TO BE MADE A JEDEC PACKAGE OUTLINE M0-229 VARIATION OF (WEED-1)
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 TOP AND BOTTOM OF PACKAGE
MS8 Package
8-Lead Plastic MSOP
(Reference LTC DWG # 05-08-1660 Rev F)
3.00 ± 0.102
(.118 ± .004)
(NOTE 3)
0.52
(.0205)
REF
8
7
6 5
3.00 ± 0.102
(.118 ± .004)
(NOTE 4)
4.90 ± 0.152
(.193 ± .006)
0.889 ± 0.127
(.035 ± .005)
DETAIL “A”
0° – 6° TYP
0.254
(.010)
GAUGE PLANE
5.23
(.206)
MIN
1
2
3
4
3.20 – 3.45
(.126 – .136)
0.53 ± 0.152
(.021 ± .006)
1.10
(.043)
MAX
0.86
(.034)
REF
DETAIL “A”
0.18
(.007)
0.65
(.0256)
BSC
0.42 ± 0.038
(.0165 ± .0015)
SEATING
PLANE
TYP
0.22 – 0.38
0.1016 ± 0.0508
RECOMMENDED SOLDER PAD LAYOUT
(.009 – .015)
(.004 ± .002)
0.65
(.0256)
BSC
TYP
NOTE:
MSOP (MS8) 0307 REV F
1. DIMENSIONS IN MILLIMETER/(INCH)
2. DRAWING NOT TO SCALE
3. DIMENSION DOES NOT INCLUDE MOLD FLASH, PROTRUSIONS OR GATE BURRS.
MOLD FLASH, PROTRUSIONS OR GATE BURRS SHALL NOT EXCEED 0.152mm (.006") PER SIDE
4. DIMENSION DOES NOT INCLUDE INTERLEAD FLASH OR PROTRUSIONS.
INTERLEAD FLASH OR PROTRUSIONS SHALL NOT EXCEED 0.152mm (.006") PER SIDE
5. LEAD COPLANARITY (BOTTOM OF LEADS AFTER FORMING) SHALL BE 0.102mm (.004") MAX
3499fc
14
LTC3499/LTC3499B
REVISION HISTORY (Revision history begins at Rev C)
REV
DATE
DESCRIPTION
PAGE NUMBER
C
3/11
Updated Pin Functions for Pins 4 and 9.
6
Corrected typo in Equation from f
to f
.
11
RPHZ
RHPZ
3499fc
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.
15
LTC3499/LTC3499B
TYPICAL APPLICATION
Two Cells to 3.3V, 250mA
Two Cells to 5V Efficiency
100
90
100000
10000
L
4.7µH
EFFICIENCY
C
V
+
IN
IN
2.2µF
V
IN
2 AA CELLS
SW
OUT
FB
80
70
1000
100
×5R
1.8V TO 3.2V
LTC3499
V
OUT
V
3.3V
ON OFF
SHDN
VC
250mA
562k
332k
C
OUT
60
50
40
10
1
10µF
POWER LOSS
100k
×5R
SS
V
V
V
= 3V
= 2.4V
= 1.8V
GND
IN
IN
IN
330pF
0.01µF
0.1
0.1
1
10
100
1000
C
C
: TAIYO YUDEN X5R JMK212BJ225MD
IN
: TAIYO YUDEN X5R JMK212BJ106MD
LOAD CURRENT (mA)
OUT
3499 F06a
L: COILCRAFT MSS5131-472MB
3499 F06b
RELATED PARTS
PART NUMBER
DESCRIPTION
COMMENTS
LT1930/LT1930A
1A (I ), 1.2MHz/2.2MHz, High Efficiency Step-Up
High Efficiency, V : 2.6V to 16V, V
SD
= 34V, I = 4.2mA/5.5mA,
OUT(MAX) Q
SW
IN
DC/DC Converter
I
< 1µA, ThinSOT Package
LT1961
1.5A (I ), 1.25MHz, High Efficiency Step-Up
90% Efficiency, V : 3V to 25V, V
SD
= 35V, I = 0.9mA,
OUT(MAX) Q
SW
IN
DC/DC Converter
I
< 6µA, MS8E Package
LTC3400/LTC3400B
LTC3401
600mA (I ), 1.2MHz, Synchronous Step-Up
92% Efficiency, V : 0.5V to 5V, V
SD
= 5V, I = 19µA/300µA,
SW
IN
OUT(MAX) Q
DC/DC Converter
I
< 1µA, ThinSOT Package
1A (I ), 3MHz, Synchronous Step-Up DC/DC Converter
97% Efficiency, VIN: 0.5V to 5V, V
= 5.5V, I = 38µA,
Q
SW
OUT(MAX)
I
SD
< 1µA, 10-Lead MS Package
LTC3402
2A (I ), 3MHz, Synchronous Step-Up DC/DC Converter
97% Efficiency, VIN: 0.5V to 5V, V
< 1µA, 10-Lead MS Package
= 5.5V, I = 38µA,
Q
SW
OUT(MAX)
I
SD
LTC3421
3A (I ), 3MHz, Synchronous Step-Up DC/DC Converter
95% Efficiency, V : 0.5V to 4.5V, V
SD
= 5.25V, I = 12µA,
Q
SW
IN
OUT(MAX)
OUT(MAX)
OUT(MAX)
with Output Disconnect
I
< 1µA, 24-Lead QFN Package
LTC3422
1.5A (I ), 3MHz, Synchronous Step-Up DC/DC
95% Efficiency, V : 0.5V to 4.5V, V
= 5.25V, I = 25µA,
Q
SW
IN
Converter with Output Disconnect
I
SD
< 1µA
LTC3425
5A (I ), 8MHz, 4-Phase Synchronous Step-Up DC/DC
95% Efficiency, V : 0.5V to 4.5V, V
= 5.25V, I = 12µA,
Q
SW
IN
Converter with Output Disconnect
I
SD
< 1µA, 32-Lead QFN Package
LTC3427
500mA (I ), 1.25MHz, Synchronous Step-Up DC/DC
94% Efficiency, V : 1.8V to 5V, V
= 5.25V, I < 1µA,
OUT(MAX) SD
SW
IN
Converter with Soft-Start/Output Disconnect
DFN Package
LTC3429/LTC3429B
LTC3458/LTC3458L
LTC3525
600mA (I ), 550kHz, Synchronous Step-Up DC/DC
92% Efficiency, V : 0.5V to 4.3V, V
SD
= 5V, I = 20µA,
OUT(MAX) Q
SW
IN
Converters with Soft-Start/Output Disconnect
I
< 1µA, ThinSOT Package
1.4A/1.7A (I ), 1.5MHz, Synchronous Step-Up DC/DC
93% Efficiency, V : 1.5V to 6V, V
SD
= 7.5V/6V, I = 15µA,
SW
IN
OUT(MAX) Q
Converter with Soft-Start/Output Disconnect
I
< 1µA, DFN Package
400mA (I ), Synchronous Step-Up DC/DC
94% Efficiency, V : 0.5V to 4.5V, V
= 5.25V, I = 7µA,
OUT(MAX) Q
SW
IN
Converter in SC70
I
SD
< 1µA, Output Disconnect
3499fc
LT 0311 REV C • PRINTED IN USA
LinearTechnology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
16
●
●
LINEAR TECHNOLOGY CORPORATION 2006
(408) 432-1900 FAX: (408) 434-0507 www.linear.com
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