LINEAR TECHNOLOGY LT1976 LT1976B Specifications User Guide

POW ER LOSS (W

LT1976/LT1976B

High Voltage 1.5A, 200k Hz Step-Down Switching Regulator with 100µA Quiescent Current

FEATURES DESCRIPTIO

Wide Input Range: 3.3V to 60V The LT®1976/LT1976B are 200k Hz monolithic step-down 1.5A Peak Switch Current (LT1976) switching regulators that accept input voltages up to 60V. 100µA Quiescent Current (LT1976)** A high efficiency 1.5A, 0.2Ω switch is included on the die 1.6m A Quiescent Current (LT1976B) along with all the necessary oscillator, control and logic Low Shutdown Current: IQ < 1µA 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-

200k Hz Switching Frequency SU PP LY UR RE NT (µ A)

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 maintains peak switch current over the full duty cycle

APPLICATIO S

range.* Shutdown reduces input supply current to less

High Voltage Power Conversion EF FI CI EN CY 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.

TYPICAL APPLICATIO

LT1976 Supply Current vs LT1976 Efficiency and Power

14V to 3.3V Step-Down Converter with Input Voltage Loss vs Load Current 100µA No Load Quiescent Current

VOUT = 3.3V TA = 25°C EFFICIENCY

VIN BOOST 3.3V

3.3V TO 60V

100V SHDN

SW 5V

CER LT1976 0.1µF 3.3V

10MQ60N

VC CSS 0.1

VBIAS TYPICAL

165k POWER LOSS

10k FB 1% 100µF

CT 0.01

1µF SYNC TANT

GND PG 1%

1976 TA01 0.1

INPUT VOLTAGE (V) 1976 F05 LOAD CURRENT (m A) 1976 TA02

1976bfe