LT3437
High Voltage 500mA, 200kHz
Step-Down Switching Regulator
with 100µA Quiescent Current
DESCRIPTIO
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FEATURES
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The LT®3437 is a 200kHz monolithic buck switching
regulator that accepts input voltages up to 80V. A high
efficiency 500mA, 0.8Ω switch is included on the die along
with all the necessary oscillator, control and logic circuitry. Current mode topology is used for fast transient
response and good loop stability.
Wide Input Range: 3.3V to 60V
Load Dump (Input Transient) Protection to 80V
500mA Peak Switch Current
Burst Mode® Operation: 100µA Quiescent Current**
Low Shutdown Current: IQ < 1µA
Defeatable Burst Mode Operation
200kHz Switching Frequency
Saturating Switch Design: 0.8Ω On-Resistance
Peak Switch Current Maintained Over
Full Duty Cycle Range*
1.25V Feedback Reference Voltage
Easily Synchronizable
Soft-Start Capability
Small 10-Pin Thermally Enhanced DFN Package
Innovative design techniques along with a new high voltage process achieve high efficiency over a wide input
range. Efficiency is maintained over a wide output current
range by employing Burst Mode operation at low currents,
utilizing the output to bias the internal circuitry, and by
using a supply boost capacitor to fully saturate the power
switch. Burst Mode operation can be defeated by a logic
high signal on the SYNC pin which results in lower light
load ripple at the expense of light load efficiency. Patented
circuitry maintains peak switch current over the full duty
cycle range.* Shutdown reduces input supply current to
less than 1µA. External synchronization can be implemented by driving the SYNC pin with logic-level inputs. A
single capacitor from the CSS pin to the output provides a
controlled output voltage ramp (soft-start).
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APPLICATIO S
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High Voltage Power Conversion
14V and 42V Automotive Systems
Industrial Power Systems
Distributed Power Systems
Battery-Powered Systems
Powered Ethernet
The LT3437 is available in a low profile (0.75mm) 3mm ×
3mm 10-pin DFN package or a 16-Pin TSSOP Package,
both with exposed pad leadframes for low thermal
resistance.
, 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. *Protected by U.S. Patents, including 6498466.
**See Burst Mode Operation section for conditions.
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TYPICAL APPLICATIO
14V to 3.3V Step-Down Converter with
100µA No Load Quiescent Current
2.2µF
100V
CER
VIN
BOOST
0.1µF
SHDN
SW
LT3437
VC
1500pF
200
330pF
0.1µF
100µH BAS21
VOUT
3.3V
400mA
10MQ100N
CSS
VBIAS
27pF
25k
SYNC
165k
FB
GND
*FOR INPUT VOLTAGES ABOVE 60V RESTRICTIONS APPLY
100k
100µF
6.3V
TANT
180
160
SUPPLY CURRENT (µA)
VIN
4.5V TO 80V*
Input Voltage
Transient Response
Supply Current vs Input Voltage
VIN
20V/DIV
140
120
VIN
0V
100
80
VOUT
20mV/DIV
AC COUPLED
60
40
IOUT 250mA
20
3437 TA01
LOAD DUMP
3437 TA03
50ms/DIV
COLD CRANK
0
0
10
20
30 40 50 60
INPUT VOLTAGE (V)
70
80
3437 TA02
3437fc
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