Datasheet LT1977 (Analog Devices)

LT1977 High Voltage 1.5A, 500kHz Step-Down Switching Regulator with 100µA Quiescent Current
U FEATURES DESCRIPTIO
■
Wide Input Range: 3.3V to 60V
The LT®1977 is a 500kHz monolithic buck switching ■
1.5A Peak Switch Current
regulator that accepts input voltages up to 60V. A high ■
Burst Mode® Operation: 100
µ
A Quiescent Current**
efficiency 1.5A, 0.2Ω switch is included on the die along ■
Low Shutdown Current: IQ < 1
µ
A
with all the necessary oscillator, control and logic cir- ■
Power Good Flag with Programmable Threshold
cuitry. Current mode topology is used for fast transient ■
Load Dump Protection to 60V
response and good loop stability. ■ 500kHz Switching Frequency Innovative design techniques along with a new high volt- ■ Saturating Switch Design: 0.2Ω 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. Patented circuitry maintains peak switch current ■ Small 16-Pin Thermally Enhanced TSSOP Package over the full duty cycle range.* Shutdown reduces input supply current to less than 1µA. External synchronization
U
can be implemented by driving the SYNC pin with logic-level
APPLICATIO S
inputs. A single capacitor from the CSS pin to the output ■ High Voltage Power Conversion provides a controlled output voltage ramp (soft-start). The ■ 14V and 42V Automotive Systems device also has a power good flag with a programmable ■ Industrial Power Systems threshold and time-out and thermal shutdown protection. ■ Distributed Power Systems ■ Battery-Powered Systems The LT1977 is available in a 16-pin TSSOP package with exposed pad leadframe for low thermal resistance. The , LTC and LT are registered trademarks of Linear Technology Corporation. Burst Mode is a registered trademark of Linear Technology Corporation. LT1976, a 200kHz reduced switch frequency version of the *Protected by U.S. Patents including 6498466, 6531909. **See Burst Mode Operation section for conditions LT1977, is also available. See the Applications Information section for selection criteria between the LT1976 and LT1977.
U Efficiency and Power Loss TYPICAL APPLICATIO Supply Current vs Input Voltage vs Load Current 14V to 3.3V Step-Down Converter with
150 100 10 V V OUT = 3.3V IN = 12V
100
µ
A No Load Quiescent Current
TA = 25°C VOUT = 5V 125 75 1 POWER LOSS (W) VOUT µA) 100 V V IN V OUT = 3.3V IN BOOST 3.3V 2.2µF 0.1µF 10µH 1A SHDN 1N4148 100V SW 75 50 0.1 CER LT1977 0.1µF 10MQ100N TYPICAL V C C SS 50 EFFICIENCY (%) POWER LOSS 1500pF 330pF VBIAS SUPPLY CURRENT ( 25 0.01 165k 26k FB 10pF 25 1% + 100µF CT PGFB 6.3V 1µF SYNC TANT 100k 0 0 0.001 GND PG 1% 0 10 20 30 40 50 60 0.0001 0.001 0.01 0.1 1 10 INPUT VOLTAGE (V) LOAD CURRENT (A) 1977 TA01 1977 F05 1977 TA02 1977fa 1