ISSI IS31LT3957 | Demoboard IS31LT3957-ZLS4-EBSEPIC

Description

The IS31LT3957 is a current mode PWM controller designed to drive a low side external NMOS FET for wide input/output voltage range and high LED current applications. An external resistor senses the high side output current of the LED string. A high side sense is the most flexible current sensing scheme, since it functions in either boost or buck-boost mode configurations. The controller can be configured with an external resistor to operate between 100kHz~1MHz frequency resulting in small external inductor and capacitors while maintaining high efficiency. A single capacitor is all that is required to set the spread spectrum dither frequency to reduce the radiated peak emission and optimize the system EMI performance.

Features

• Wide high voltage input range: 5V to 75V
• Supports boost, buck-boost, SEPIC and buck topology
• ±2% output current accuracy
• Adjustable operating frequency range of 100kHz~1MHz
• Programmable soft start to avoid inrush current
• Fixed under voltage lockout threshold
• EMI reduction capabilities
• Programmable spread spectrum function
• Operating frequency synchronization with external clock source
• Supports either analog or PWM dimming
• Fault protection with reporting:
• VCC under voltage lockout (not reported)
• Programmable output over voltage protection
• Output short circuit protection
• RT/SYNC pin short protection
• VDD pin short protection
• VDD under voltage lockout (not reported)
• Over temperature protection

Typical applications

• General high power LED, Architecture lighting, Motorcycle headlight, Exit Signs and Emergency Lighting

More information

• IC product information