LT3437 Datasheet, PDF (1/24 Pages) Linear Technology – High Voltage 500mA, 200kHz Step-Down Switching Regulator with 100uA Quiescent Current

LT3437
High Voltage 500mA, 200kHz
Step-Down Switching Regulator
with 100µA Quiescent Current
FEATURES
■ _{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}
■ _{Burst Mode Operation Defeat}
■ _{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}
U
APPLICATIO S
■ _{High Voltage Power Conversion}
■ _{14V and 42V Automotive Systems}
■ _{Industrial Power Systems}
■ _{Distributed Power Systems}
■ _{Battery-Powered Systems}
■ _{Powered Ethernet}
, LTC and LT 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.
DESCRIPTIO
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 cir-
cuitry. Current mode topology is used for fast transient
response and good loop stability.
Innovative design techniques along with a new high volt-
age 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 imple-
mented by driving the SYNC pin with logic-level inputs. A
single capacitor from the C_SS pin to the output provides a
controlled output voltage ramp (soft-start).
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.
TYPICAL APPLICATIO
14V to 3.3V Step-Down Converter with
100µA No Load Quiescent Current
V_IN
4.5V TO 80V*
1500pF
25k
2.2µF
100V
CER
330pF
V_IN BOOST
SHDN
SW
0.1µF 100µH _BAS21
LT3437 0.1µF
10MQ100N
V_C
C_SS
V_BIAS
27pF
165k
SYNC
FB
GND
100k
V_OUT
3.3V
400mA
100µF
6.3V
TANT
*FOR INPUT VOLTAGES ABOVE 60V RESTRICTIONS APPLY
3437 TA01
Supply Current vs Input Voltage
Input Voltage
Transient Response
200
180
160
140
120
100
80
60
40
20
0
0
V_IN
20V/DIV
V_IN
0V
V_OUT
20mV/DIV
AC COUPLED
I_OUT 250mA
LOAD DUMP
50ms/DIV
3437 TA03
COLD CRANK
10 20 30 40 50 60 70 80
INPUT VOLTAGE (V)
3435 TA02
3437f
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