POWER LOSS (W) LT1977 High Voltage 1.5A, 500kHz Step-Down Switching Regulator with 100A Quiescent Current FEATURES DESCRIPTIO The LT 1977 is a 500kHz monolithic buck switching Wide Input Range: 3.3V to 60V regulator that accepts input voltages up to 60V. A high 1.5A Peak Switch Current efficiency 1.5A, 0.2 switch is included on the die along Burst Mode Operation: 100A Quiescent Current** with all the necessary oscillator, control and logic cir- Low Shutdown Current: I < 1A Q cuitry. Current mode topology is used for fast transient Power Good Flag with Programmable Threshold response and good loop stability. Load Dump Protection to 60V 500kHz Switching Frequency Innovative design techniques along with a new high volt- Saturating Switch Design: 0.2 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 1A. External synchronization U can be implemented by driving the SYNC pin with logic-level APPLICATIO S inputs. A single capacitor from the C pin to the output SS 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 The LT1977 is available in a 16-pin TSSOP package with Battery-Powered Systems 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. Efficiency and Power Loss TYPICAL APPLICATIO vs Load Current Supply Current vs Input Voltage 10 100 150 14V to 3.3V Step-Down Converter with V = 12V V = 3.3V IN OUT = 25C T 100A No Load Quiescent Current A V = 5V OUT 125 1 75 V OUT 100 V = 3.3V OUT V V BOOST 3.3V IN IN 2.2F 10H 1A 0.1F 1N4148 SHDN 100V SW 50 75 0.1 CER LT1977 0.1F 10MQ100N TYPICAL V C 50 POWER LOSS C SS 330pF 1500pF V 25 0.01 BIAS 165k 10pF 25 26k FB 1% + 100F C T 6.3V PGFB 1F SYNC 0.001 TANT 0 0 100k PG 0 10 20 30 40 50 60 0.0001 0.001 0.01 0.1 1 10 GND 1% INPUT VOLTAGE (V) LOAD CURRENT (A) 1977 TA01 1977 TA02 1977 F05 1977fa 1 SUPPLY CURRENT (A) EFFICIENCY (%) U ULT1977 UUW ABSOLUTE AXI U RATI GS PACKAGE/ORDER I FOR ATIO (Note 1) TOP VIEW V , SHDN, BIAS, SW, PG....................................... 60V ORDER PART IN NC 1 16 PG BOOST Pin Above SW ............................................ 35V NUMBER SW 2 15 SHDN BOOST Pin Voltage ................................................. 68V LT1977EFE NC 3 14 SYNC SYNC, C , PGFB, FB................................................ 6V SS LT1977IFE V 4 13 PGFB IN Operating JunctionTemperature Range 17 NC 5 12 FB LT1977EFE (Note 2) ........................ 40C to 125C BOOST 6 11 V C LT1977IFE (Note 2) ......................... 40C to 125C C 7 10 BIAS T FE PART Storage Temperature Range ................. 65C to 150C GND 8 9 C SS MARKING Lead Temperature (Soldering, 10 sec).................. 300C FE PACKAGE 16-LEAD PLASTIC TSSOP 1977EFE T = 125C, = 45C/W, = 10C/W JMAX JA JC(PAD) 1977IFE EXPOSED PAD IS GND (PIN 17) MUST BE SOLDERED TO GND (PIN 8) Order Options Tape and Reel: Add TR Lead Free: Add PBF Lead Free Tape and Reel: Add TRPBF Lead Free Part Marking: