Datasheet LT3437 (Analog Devices)

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