Datasheet LT1976, LT1976B (Analog Devices)

LT1976/LT1976B High Voltage 1.5A, 200kHz Step-Down Switching Regulator with 100μA Quiescent Current
U FEATURES DESCRIPTIO
■
Wide Input Range: 3.3V to 60V
The LT®1976/LT1976B are 200kHz monolithic step-down ■
1.5A Peak Switch Current (LT1976)
switching regulators that accept input voltages up to 60V. ■
100
μ
A Quiescent Current (LT1976)**
A high efficiency 1.5A, 0.2Ω switch is included on the die ■
1.6mA Quiescent Current (LT1976B)
along with all the necessary oscillator, control and logic ■
Low Shutdown Current: IQ < 1
μ
A
circuitry. Current mode topology is used for fast transient ■
Power Good Flag with Programmable Threshold
response and good loop stability. ■
Load Dump Protection to 60V
Innovative design techniques along with a new high volt- ■ 200kHz Switching Frequency age process achieve high efficiency over a wide input ■ Saturating Switch Design: 0.2Ω On-Resistance range. Efficiency is maintained over a wide output current ■ Peak Switch Current Maintained Over range by employing Burst Mode operation at low currents, Full Duty Cycle Range* utilizing the output to bias the internal circuitry, and by ■ 1.25V Feedback Reference Voltage using a supply boost capacitor to fully saturate the power ■ Easily Synchronizable switch. The LT1976B does not shift into Burst Mode ■ Soft-Start Capability operation at low currents, eliminating low frequency out- ■ Small 16-Pin Thermally Enhanced TSSOP Package put ripple at the expense of efficiency. Patented circuitry
U
maintains peak switch current over the full duty cycle
APPLICATIO S
range.* Shutdown reduces input supply current to less ■ High Voltage Power Conversion than 1μA. External synchronization can be implemented ■ 14V and 42V Automotive Systems by driving the SYNC pin with logic-level inputs. A single ■ Industrial Power Systems capacitor from the CSS pin to the output provides a ■ Distributed Power Systems controlled output voltage ramp (soft-start). The devices ■ Battery-Powered Systems also have a power good flag with a programmable thresh- old and time-out and thermal shutdown protection. , 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. The LT1976/LT1976B are available in a 16-pin TSSOP *Protected by U.S. Patents, including 6498466 **See Burst Mode Operation section for conditions package with Exposed Pad leadframe for low thermal resistance.
U TYPICAL APPLICATIO LT1976 Supply Current vs LT1976 Efficiency and Power 14V to 3.3V Step-Down Converter with Input Voltage Loss vs Load Current 100
μ
A No Load Quiescent Current
150 100 10 VOUT = 3.3V TA = 25°C EFFICIENCY VOUT V 125 IN VIN BOOST 3.3V 3.3V TO 60V 4.7μF 75 1 0.33μF 33μH 1A POWER LOSS (W) SHDN 4148 μA) 100V SW 100 5V CER LT1976 0.1μF 3.3V 10MQ60N V 75 50 0.1 C CSS 1500pF 330pF VBIAS TYPICAL 165k 47pF 50 EFFICIENCY (%) POWER LOSS 10k FB 1% 100μF C SUPPLY CURRENT ( T 6.3V 25 0.01 PGFB 1μF SYNC TANT 100k 25 GND PG 1% 0 0 0.001 1976 TA01 0 10 20 30 40 50 60 0.1 1 10 100 1000 10000 INPUT VOLTAGE (V) 1976 F05 LOAD CURRENT (mA) 1976 TA02 1976bfg 1