LINER LT3653 1.2a, hv input regulator with output current limit for battery charger application Datasheet

LT3653
1.2A, HV Input Regulator
with Output Current Limit for
Battery Charger Applications
DESCRIPTION
FEATURES
n
n
n
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Wide Input Range:
– Operation from 7.5V to 30V
– Overvoltage Lockout Protects Circuit Through 60V
Transients
Operates with LTC Bat-Track™ Li-Ion Battery
Chargers to Maximize Efficiency
No Reverse Discharge Path from VOUT to VIN
Programmable Output Current Limit
Integrated BOOST Diode
Thermal Protection
Small Application Size
Thermally Enhanced 2mm × 3mm DFN Package
The LT®3653 is a monolithic current mode PWM step-down
regulator with programmable output current limit. Typically,
it is used with battery charger power path controllers to
pre-regulate the output and optimize the battery charger
efficiency. Output current limit provides accurate control
over system power dissipation.
The wide operating input voltage range of 7.5V to 30V
suits the LT3653 to a variety of input sources, including
unregulated 12V wall adapters, 24V industrial supplies,
Firewire and automotive power. Input overvoltage protection allows the LT3653 to handle 60V input transients.
The LT3653 control pin, VC , is available for external battery
tracking control, Bat-Track. The LT3653 will block output
discharge during an open or shorted input.
APPLICATIONS
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n
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Battery Powered Equipment
Portable USB Devices – Cameras, MP3 Players,
PDAs
Automotive Battery Regulation
Multiple-Source Battery Chargers
The HVOK pin indicates that the internal bias supplies
are present and no faults have occurred (i.e., overtemperature and input overvoltage and undervoltage). The
LT3653 includes a 1.5MHz frequency oscillator, internal
compensation, and an internal boost diode to minimize the
number of external components. The LT3653 is available
in an 8-lead (2mm × 3mm) package with exposed pads
for low thermal resistance.
, LT, LTC and LTM are registered trademarks of Linear Technology Corporation.
Bat-Track is a trademark of Linear Technology Corporation. All other trademarks are the
property of their respective owners.
TYPICAL APPLICATION
Efficiency vs Load Current
High Voltage Single-Cell Battery Charger Application
100
0.1μF
BOOST
VIN
4.7μF
90
SW
4.7μH
LT3653
ISENSE
ILIM
1.2A
SYSTEM
LOAD
VOUT
10μF
27.4k
EFFICIENCY (%)
VIN
7.5V TO 30V
TRANSIENT
TO 60V
VIN = 8V
80
70
VIN = 12V
VIN = 24V
60
OUT
HVOK
GND
VC
3653 TA01a
WALL
LTC4098
VC
BAT
+
SINGLE-CELL
Li-Ion
50
40
0.1
0.3
0.7
0.5
0.9
OUTPUT CURRENT(A)
1.1
1.3
3653 TA01a
3653f
1
LT3653
ABSOLUTE MAXIMUM RATINGS
PIN CONFIGURATION
(Note 1)
Input Voltage (VIN) (Note 3) ......................................60V
Boost Pin Voltage (BOOST).......................................50V
Boost Pin Above SW Pin ...........................................25V
HVOK, VOUT, ISENSE Pins .............................................6V
VC Pin .........................................................................3V
Operating Junction Temperature Range (Notes 2, 5)
LT3653E .............................................–40°C to 125°C
LT3653I ..............................................–40°C to 125°C
Storage Temperature..............................–65°C to 150°C
TOP VIEW
8 SW
VIN 1
HVOK 2
9
7 BOOST
VC 3
6 ISENSE
ILIM 4
5 VOUT
DCB PACKAGE
8-LEAD (2mm s 3mm) PLASTIC DFN
θJA = 64°C/W, θJC = 10°C/W
EXPOSED PAD (PIN 9) IS GND, MUST BE SOLDERED TO PCB
ORDER INFORMATION
LEAD FREE FINISH
TAPE AND REEL
PART MARKING*
PACKAGE DESCRIPTION
TEMPERATURE RANGE
LT3653EDCB#PBF
LT3653EDCB#TRPBF
LDJN
8-Lead (2mm × 3mm) Plastic DFN
–40°C to 125°C
LT3653IDCB#PBF
LT3653IDCB#TRPBF
LDJN
8-Lead (2mm × 3mm) Plastic DFN
–40°C to 125°C
Consult LTC Marketing for parts specified with wider operating temperature ranges. *The temperature grade is identified by a label on the shipping container.
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 the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C; VIN = 12V, VBOOST = 17V, VSW = 0V, RILIM = 33.2k, unless otherwise noted.
PARAMETER
CONDITIONS
l
VIN Operating Range
VIN Undervoltage Lockout
MIN
7.5
Rising
6.5
Rising
30
VIN Undervoltage Hysteresis
VIN Overvoltage Lockout
7
MAX
33
V
7.5
V
mV
36
1
VIN Supply Current
Not Switching
VOUT Reverse Leakage Current
VIN = 0V, VOUT = 4.8V
VIN = Open, VOUT = 4.8V
VOUT Nominal Set Point
VC Pin = Open
VOUT Current Limit Range
RILIM = 33.2k
Operating Frequency
2.8
4.8
UNITS
30
500
VIN Overvoltage Lockout Hysteresis
VOUT Current Limit
TYP
V
V
3.4
mA
1
1
μA
μA
5
V
1.2
A
l
0.4
l
0.85
0.80
1
1
1.15
1.2
A
A
l
1350
1500
1650
kHz
VC Source Current
VOUT = 0V, VC = 1.5V
12
μA
VC Sink Current
VOUT = 5V, VC = 1.5V
10
μA
VC Switching Threshold
IOUT = 0mA
1.1
V
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2
LT3653
ELECTRICAL CHARACTERISTICS
The l denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C; VIN = 12V, VBOOST = 17V, VSW = 0V, RILIM = 33.2k, unless otherwise noted.
PARAMETER
CONDITIONS
MIN
VC Clamp Voltage
VOUT = 0V
1.75
V
Switch Peak Current Limit
(Note 4)
2
A
Switch VCESAT
ISW = 1A
275
Boost Diode Drop
IDIODE = 60mA
0.9
Boost Pin Current
ISW = 1A
MAX
HVOK Output Voltage High
IHVOK = 1mA
HVOK Output Voltage Low
IHVOK = –2μA
l
4
4.4
UNITS
mV
1.2
28
l
Note 1: Stresses beyond those listed under Absolute Maximum Ratings
may cause permanent damage to the device. Exposure to any Absolute
Maximum Rating condition for extended periods may affect device
reliability and lifetime.
Note 2: The LT3653E is guaranteed to meet performance specifications
from 0°C to 125°C. Specifications over the –40°C to 125°C operating
temperature range are assured by design, characterization, and correlation
with statistical process controls. The LT3653I specifications are
guaranteed over the full –40°C to 125°C temperature range. High junction
temperatures degrade operating lifetimes. Operating lifetime is derated at
junction temperatures greater than 125°C.
TYP
V
mA
5
V
0.25
V
Note 3: Absolute Maximum Voltage at VIN pin is 60V for non-repetitive
1 second transients.
Note 4: Switch Peak Current Limit guaranteed by design and/or correlation
to static test.
Note 5: This IC includes overtemperature protection that is intended
to protect the device during momentary overload conditions. Junction
temperature will exceed the maximum operating junction temperature
when overtemperature protection is active. Continuous operation above
the specified maximum operating junction temperature may impair device
reliability.
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3
LT3653
TYPICAL PERFORMANCE CHARACTERISTICS
Switch Voltage Drop
Switching Frequency
125ºC
25ºC
300
250
–45ºC
200
150
100
SWITCHING FREQUENCY (MHz)
350
Undervoltage Lockout
1.7
8.0
1.6
7.5
RISING
7.0
1.5
INPUT VOLTAGE (V)
400
SWITCH VOLTAGE DROP (mV)
TA = 25°C unless otherwise noted
1.4
1.3
1.2
0
0
0.2
0.4
0.6
0.8
SWITCH CURRENT (A)
1
-25
0
25
50
75
TEMPERATURE (ºC)
100
3653 G01
4.0
–50 -25
125
0
25 50 75 100 125 150
TEMPERATURE (ºC)
3653 G03
3653 G02
Output Current Limit
Output Current Limit
VIN Overvoltage Lockout
6
1.2
RILIM = 33.2k
RILIM = 27.4k
1.15
35
RISING
OUTPUT VOLTAGE (V)
1.05
1
0.95
INPUT VOLTAGE (V)
5
1.1
CURRENT LIMIT (A)
5.5
4.5
1.0
–50
1.2
FALLING
6.0
5.0
1.1
50
6.5
4
3
2
33
FALLING
31
29
0.9
27
1
0.85
0.8
–50 –25
0
25
50
75
TEMPERATURE (ºC)
100
0
125
0
0.2
0.4 0.6 0.8
1
OUTPUT CURRENT (A)
1.2
BOOST Pin Current
0
25
50
75
TEMPERATURE (ºC)
100
125
3653 G06
Boost Diode VF
35
1.4
30
1.2
25
1
BOOST DIODE VF (V)
BOOST PIN CURRENT (mA)
–25
3653 G05
3653 G04
20
15
10
0.8
0.6
0.4
0.2
5
0
25
–50
1.4
0
0.2
0.4
0.5
0.8
SWITCH CURRENT (A)
1
1.2
3653 G07
0
0
50
100
150
200
DIODE CURRENT (mA)
250
300
3653 G08
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4
LT3653
TYPICAL PERFORMANCE CHARACTERISTICS
VC Operating Range
15
2.0
10
1.8
CURRENT LIMIT CLAMP
1.6
5
VC VOLTAGE (V)
VC PIN CURRENT (μA)
VC Current
TA = 25°C unless otherwise noted
0
–5
–10
1.4
1.2
1.0
SWITCHING THRESHOLD
0.8
0.6
–15
0.4
–20
0.2
–25
4
4.4
4.8
5.2
VOUT (V)
5.6
6
3653 G09
0.0
-50
-25
0
25
50
75
TEMPERATURE (ºC)
100
125
3653 G10
PIN FUNCTIONS
VIN (Pin 1): The VIN pin supplies current to the LT3653’s
internal regulator and the internal power switch. Locally
bypass this pin with a capacitor.
HVOK (Pin 2): The HVOK pin is a status pin which indicates that the internal bias rail is present and that an input
undervoltage lockout fault, an overvoltage lockout fault or
an over temperature fault are not present.
VC (Pin 3): The VC pin is the output of the internal error
amplifier and is internally compensated. The voltage on this
pin controls the peak switch current. Connect this pin to
the battery charger VC pin for battery tracking function.
ILIM (Pin 4): Connect a resistor to GND to program the
output current limit of the regulator. See the ILIM Resistor
section in Application Information.
VOUT (Pin 5): The VOUT pin is connected to the negative
terminal of the internal current sense resistor of the output
current limit circuit. Maximum VOUT voltage is regulated
to 4.8V.
ISENSE (Pin 6): The ISENSE pin is the positive input to the
internal current sense resistor of the output current limit
circuit. The ISENSE pin is also the anode of the internal
BOOST diode.
BOOST (Pin 7): The BOOST pin provides a drive voltage,
higher than the input voltage, to the internal power switch.
The BOOST pin is internally connected to the cathode of
the BOOST diode.
SW (Pin 8): The SW pin is the output of the internal power
switch. Connect this pin to the inductor, catch diode and
boost capacitor.
Exposed Pad (Pin 9): Ground. The Exposed Pad must be
soldered to the PCB and electrically connected to ground.
Use a large ground plane and vias to optimize thermal
performance.
3653f
5
LT3653
BLOCK DIAGRAM
LT3653
VIN
VIN
RSENSE1
Q1
L1
SW
C1
D1
C3
–
+
BOOST
A1
3
+
Q
R
–
INTERNAL BIAS
REGULATORS,
REFERENCE,
UVLO AND OVP
S
D2
OSCILLATOR
AND
SLOPE
COMPENSATION
ISENSE
HVOK
TO
CHARGER
DRIVER
+
–
5V
G2
FAULT
RSENSE2
–
+
VOUT
SYSTEM
LOAD
C2
ILIM
R1
–
TO
CHARGER
VC
G1
INTERNAL
COMPENSATION
+
BATTERY
CHARGER
FB
+
0.8V
SINGLE-CELL Li-Ion
2.5V
REGULATOR
EXPOSED PAD
GND
3653 BD
3653f
6
LT3653
OPERATION
Please refer to the Block Diagram. The LT3653 is specifically tailored for use with a battery charger power path
controller. The LT3653 regulates the high voltage input to
a lower voltage to provide power to the system load and to
the single-cell Li-Ion battery charger. High efficiency in the
battery charger is achieved by keeping the voltage across
it low. To accomplish this, the battery charger takes control
of the LT3653 regulator control node, VC , and overrides
the error amp, G1. The output voltage is regulated by the
battery charger to a voltage slightly above the battery,
typically 300mV.
HVOK is a status pin which indicates to the charger that a
high voltage input is present and that the LT3653 is ready to
start providing power to the system load. When the HVOK
pin is low, the LT3653 is not switching and the system
output is not supported by the LT3653 regulator.
The LT3653 is a constant frequency, current mode step
down regulator. A switch cycle is initiated when the
1.5MHz oscillator enables the RS flip flop, turning on
the internal power switch, Q1. The sense amplifier (A1)
monitors the switch current via the voltage dropped
across the current sense resistor RSENSE1. The comparator compares the amplified current signal with the output
(VC) of the error amplifier (G1). The switch is turned off
when this current exceeds a value determined by the
VC voltage. The error amplifier monitors the VOUT voltage through an internal resistor divider and, when not
driven externally servos the VC voltage to regulate VOUT.
If the VOUT voltage drops, the VC voltage will be driven
higher increasing the output current and VOUT voltage.
An active clamp (not shown) on the VC node provides
current limit. The LT3653 is internally compensated with
a pole zero combination.
An external capacitor and internal diode, D2, are used to
generate a voltage at the BOOST pin that is higher than
the input supply. This allows the driver to fully saturate the
internal bipolar NPN power switch for efficient operation.
The switch driver operates from either VIN or BOOST to
ensure startup.
An internal regulator provides power to the control circuitry.
This regulator includes input undervoltage and overvoltage
protection which disables switching action when VIN is less
than 7V and greater than 33V, typical. When switching is
disabled, the LT3653 safely sustains input voltages up to
60V. Note that while switching is disabled the output will
discharge.
Output current limiting is provided via the servo action
of amplifier G2. The voltage across the sense resistor,
RSENSE2 , is compared to a voltage programmed by external resistor R1 on the ILIM pin. A capacitor averages
the inductor ripple current. If the averaged inductor current exceeds the programmed value then the VC voltage
is pulled low, reducing the current in the regulator. The
output current limit circuit allows for lower current rated
power path components and provides better control of
system power dissipation.
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7
LT3653
APPLICATIONS INFORMATION
Inductor Selection
A 4.7μH inductor is recommended for most LT3653 applications. This value provides a good tradeoff between
size and ripple current. The inductor’s RMS current rating
must be greater than the maximum load current and its
saturation current should be about 30% higher. The output
current limit circuit tightly controls the maximum average
inductor current therefore the inductor RMS current rating
does not have to be overrated to handle short-circuit or
overload conditions. For high efficiency, keep the series
resistance (DCR) less than 0.1Ω. Output voltage ripple
can be reduced by using a higher value inductor. The cost
is a larger physical size and poorer transient response.
A lower value inductor has higher ripple currents but is
physically smaller or, for the same size, has lower DCR
usually resulting in higher efficiency.
The input capacitor is required to reduce the resulting voltage ripple at the LT3653 and to force this very high frequency
switching current into a tight local loop, minimizing EMI.
Place the capacitor in close proximity to the LT3653 and
the catch diode (see the PCB Layout section).
Output Capacitor
A 10μF or greater ceramic capacitor is required for low
output ripple and good transient response. Ceramic capacitors have very low equivalent series resistance (ESR)
and provide the best ripple performance. Use X5R or X7R
types and keep in mind that a ceramic capacitor biased
with VOUT has less than its nominal capacitance.
High performance electrolytic capacitors can be used for
the output capacitor. Low ESR is important, so choose
one that is intended for use in switching regulators. Keep
the ESR less than 0.1Ω.
Catch Diode
The catch diode conducts current only during switch off
time. Average forward current in normal operation is
calculated from:
ID( AVG) =IOUT
VIN − VOUT
VIN
where IOUT is the maximum output load current programmed by the ILIM resistor. Peak reverse voltage is
equal to the regulator input voltage. Use a Schottky diode
with a reverse voltage rating greater than the maximum
input voltage. The overvoltage protection feature in the
LT3653 keeps the switch off when VIN > 33V (typical),
allowing the use of a 40V rated Schottky, even when VIN
ranges up to 60V.
ILIM Resistor
The LT3653 output current limit controls the maximum
current delivered from the LT3653 regulator. This allows
tighter control of the system power dissipation and also
protects the inductor and diode from overheating during
an overload or short-circuit condition. A resistor connected
from the ILIM pin to GND programs the output current
limit. Table 1 details the ILIM resistor values for specific
desired output current limits
Table 1. Output Current Limit vs RILIM Value
OUTPUT CURRENT LIMIT (A)
Input Capacitor
Bypass the input of the LT3653 circuit with a 4.7μF or higher
value ceramic capacitor of X7R or X5R type. Y5V types have
poor performance over temperature and applied voltage and
should not be used. If the input power source has high impedance, or there is significant inductance due to long wires
or cables, additional bulk capacitance may be necessary.
This can be provided with a low performance electrolytic
capacitor. Step-down regulators draw current from the
input supply in pulses with very fast rise and fall times.
RILIM VALUE (kΩ)
0.4
121
0.6
66.5
0.8
45.3
1
33.2
1.2
27.4
Boost Capacitor Selection
The boost capacitor is calculated with the following formula:
CBOOST =
(IOUT(MAX ) ) • VOUT
0.1V • 30 • VIN •1.5MHz
Typically, a 0.1μF capacitor is used.
3653f
8
LT3653
APPLICATIONS INFORMATION
Battery Charger Operation
Connect the control node, VC pin, of the LT3653 to the
VC pin of the battery charger power path controller. The
VC node is internally clamped; however, take care not to
overdrive the pin. The LT3653 is internally compensated
with a pole zero combination on the output of the gm
amplifier, G1. Check stability over the full input voltage
range, output load range and temperature.
Connect the HVOK node of the LT3653 to the high voltage
present pin of the charger. This is the WALL pin on the
LTC4098. The HVOK pin is capable of supplying up to 1mA
of drive current. When the HVOK pin is low the LT3653 is
not switching and the system output cannot be supported
by the LT3653 regulator. See the Typical Applications section for different configurations.
PCB Layout
Proper operation and minimum EMI requires a careful
printed circuit board layout. Figure 1 shows the recommended component placement with trace, ground plane
and via locations. Note that large, switched currents flow
in the LT3653’s VIN and SW pins, the catch diode (D1)
and the input capacitor (C1). Keep the loop formed by
these components as small as possible and tied to system
ground in only one place. Place these components, along
with the inductor and output capacitor, on the same side
of the circuit board, with their connections made on that
layer. Place a local, unbroken ground plane below these
VIN
components, and tie this ground plane to system ground
at one location, ideally at the ground terminal of the output
capacitor C2. Make the SW and BOOST nodes as short
as possible. Include vias near the exposed GND pad of
the LT3653 to help remove heat from the LT3653 to the
ground plane.
High Temperature Considerations
The die temperature of the LT3653 must not exceed
the maximum rating of 125°C. This is generally not a
concern unless the ambient temperature is above 85°C.
For higher temperatures, take care in the layout of the
circuit to ensure good heat sinking of the LT3653. Derate
the maximum load current as the ambient temperature
approaches 125°C. The die temperature is calculated by
multiplying the LT3653 power dissipation by the thermal
resistance from junction to ambient. Power dissipation
within the LT3653 is estimated by calculating the total
power loss from an efficiency measurement and subtracting
the catch diode loss. Thermal resistance depends on the
layout of the circuit board, but 64°C/W is typical for the
(2mm × 3mm) DFN (DCB) package.
Other Linear Technology Publications
Application Notes 19, 35 and 44 contain more detailed
descriptions and design information for Buck regulators
and other switching regulators. The LT1376 data sheet
has a more extensive discussion of output ripple, loop
compensation and stability testing.
GND
C1
TO CHARGER:
1
8
HVOK
2
7
VC
3
6
4
5
C3
C2
RILIM
VOUT
3653 F01
Figure 1. LT3653 PCB Layout
3653f
9
LT3653
TYPICAL APPLICATION
Dual Input High Efficiency Battery Charger and Triple Buck PMIC Application
BOOST
HIGH VOLTAGE INPUT
7.5V TO 30V
TRANSIENT
TO 60V
C1
4.7μF
50V
VIN
VBUS
C3
0.1μF
10V
SW
LT3653
L1
4.7μH
D1
ISENSE
VOUT
ILIM
R1
27.4k
VC
GND
HVOK
SYSTEM
LOAD
C2
10μF
6.3V
D3
MBR0520
VC
USB
WALL
ADAPTER
WALL
ACPR
VBUS
C2
10μF
M2
Si2333DS
C5
2.2μF
BVIN2
R2
2.1k
C3
10μF
6.3V
C6
2.2μF
CLPROG
R3
2k
BVIN1
VOUT
PROG
M1
(OPTIONAL)
IDGATE
R14
100k
R15
NTC
100k
BAT
SINGLE-CELL
Li-Ion
BAT
VNTC
NTC
CHRG
R13
510k
D2
LDO3V3
LTC3557
ILIM0
C13
1μF
L2
3.3μH
SW1
C7
10pF
ILIM1
R7
R6
1.02M 324k
C8
10μF
3.3V
25mA
ALWAYS-ON
VOUT1
3.3V
600mA
FB1
PMIC
CONTROL
EN1
L3
4.7μH
EN2
SW3
C9
10pF
EN3
R8
806k
R9
649k
C10
10μF
FB3
MODE
RST2
L4
4.7μH
RST2
R10
100k
SW1
C11
10pF
L1 = COILCRAFT, MSS6132-472MLC
M1 = VISHAY, Si 2333DS
D1 = DIODES INC., DFLS240
VOUT3
1.8V
400mA
R11
232k
R12
464k
C12
10μF
VOUT2
1.2V
400mA
FB1
GND
3653 TA02
3653f
10
LT3653
PACKAGE DESCRIPTION
DCB Package
8-Lead Plastic DFN (2mm × 3mm)
(Reference LTC DWG # 05-08-1718 Rev A)
0.70 p0.05
1.35 p0.05
3.50 p0.05
1.65 p 0.05
2.10 p0.05
PACKAGE
OUTLINE
0.25 p 0.05
0.45 BSC
1.35 REF
RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS
APPLY SOLDER MASK TO AREAS THAT ARE NOT SOLDERED
2.00 p0.10
(2 SIDES)
R = 0.05
TYP
R = 0.115
TYP
5
0.40 p 0.10
8
1.35 p0.10
1.65 p 0.10
3.00 p0.10
(2 SIDES)
PIN 1 NOTCH
R = 0.20 OR 0.25
s 45o CHAMFER
PIN 1 BAR
TOP MARK
(SEE NOTE 6)
(DCB8) DFN 0106 REV A
4
0.200 REF
1
0.23 p 0.05
0.45 BSC
0.75 p0.05
1.35 REF
BOTTOM VIEW—EXPOSED PAD
0.00 – 0.05
NOTE:
1. DRAWING IS NOT A JEDEC PACKAGE OUTLINE
2. DRAWING NOT TO SCALE
3. ALL DIMENSIONS ARE IN MILLIMETERS
4. DIMENSIONS OF EXPOSED PAD ON BOTTOM OF PACKAGE DO NOT INCLUDE
MOLD FLASH. MOLD FLASH, IF PRESENT, SHALL NOT EXCEED 0.15mm ON ANY SIDE
5. EXPOSED PAD SHALL BE SOLDER PLATED
6. SHADED AREA IS ONLY A REFERENCE FOR PIN 1 LOCATION ON THE
TOP AND BOTTOM OF PACKAGE
3653f
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 representation that the interconnection of its circuits as described herein will not infringe on existing patent rights.
11
LT3653
TYPICAL APPLICATION
Dual Input High Efficiency Battery Charger with Low Battery Start-Up and 1.2A Output Current Limit
SW
VIN
C1
4.7μF
50V
R1
27.4k
USB
WALL
ADAPTER
C4
10μF
6.3V
R4
6.04k
L1 = TDK, VLCF5020T-4R7NIR7-1
L2 = COILCRAFT, LPS4018-332MLC
M1 = VISHAY, Si 2333DS
D1 = DIODES INC., DFLS240
C3
0.1μF
10V
BOOST
HIGH VOLTAGE INPUT
7.5V TO 30V
TRANSIENT
TO 60V
TO UC
TO UC
LT3653
ILIM
VC
VBUS
GND
VC
OVGATE
D1
ISENSE
HVOK VOUT
WALL
SW
L2
3.3μH
SYSTEM
LOAD
C2
22μF
6.3V
VOUT
LTC4098
IDGATE
OVSENS
D0 - D2
CHRG
NTC
CLPROG
BAT
PROG
BATSENS
GND
3653 TA03
SEE THE LTC4098 DATASHEET FOR MORE INFORMATION
ON CONFIGURING THE NTC BATTERY TEMPERATURE
QUALIFICATION OR REDUCED IDEAL DIODE IMPEDANCE.
L1
4.7μH
C5
0.1μF
R2
3.01k
M1
(OPTIONAL)
SINGLE-CELL
Li-Ion
R3
1k
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PART NUMBER
DESCRIPTION
COMMENTS
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LT3508
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LT3685
36V with Transient Protection to 60V, 2A (IOUT), 2.4MHz,
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LT4089/-1/-5
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LT4090/-5
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USB-Compatible Switchmode Power Manager with OVP
High VIN: 38V operating, 60V transient; 66V OVP Maximizes Available
Power from USB Port, Bat-Track, “Instant-ON” Operation, 3mm x 4mm
UTQFN-20 Package
Burst Mode is a registered trademark of Linear Technology Corporation.ThinSOT is a trademark of Linear Technology Corporation.
3653f
12 Linear Technology Corporation
LT 0708 • PRINTED IN USA
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408) 432-1900 ● FAX: (408) 434-0507
●
www.linear.com
© LINEAR TECHNOLOGY CORPORATION 2008