IS32LT3957A HIGH VOLTAGE LED LIGHTING CONTROLLER WITH FAULT PROTECTION March 2020 GENERAL DESCRIPTION FEATURES The IS32LT3957A is a current mode PWM controller Wide high voltage input range: 5V to 75V designed to drive a low side external NMOS FET for Supports boost, buck-boost, SEPIC and buck wide input/output voltage range and high LED current topology applications. An external resistor senses the high side 3.5% output current accuracy over -40C ~ output current of the LED string. A high side sense is +125C temperature the most flexible current sensing scheme, since it Adjustable operating frequency range of functions in either boost or buck-boost mode 100kHz~1MHz configurations. The controller can be configured with an external resistor to operate between 100kHz~1MHz Programmable soft start to avoid inrush current frequency resulting in small external inductor and Fixed under voltage lockout threshold capacitors while maintaining high efficiency. A single EMI reduction capabilities capacitor is all that is required to set the spread - Programmable spread spectrum function spectrum dither frequency to reduce the radiated peak - Operating frequency synchronization with emission and optimize the system EMI performance. external clock source The IS32LT3957A integrates circuity to detect output Supports either analog or PWM dimming open/short, RT/SYNC pin short, VDD short, VCC Fault protection with reporting: under voltage lockout and over temperature fault - VCC under voltage lockout (not reported) conditions. These failure conditions can be reported by - Programmable output over voltage protection the open drain fault reporting FAULTB pin. - Output short circuit protection An MCU can be easily interfaced with the - RT/SYNC pin short protection IS32LT3957A to perform dimming control and respond - VDD pin short protection to fault report conditions. Dimming can be either - VDD under voltage lockout (not reported) analog and/or PWM input. An input DC voltage in the range of 0.1V ~ 1.1V on the ICTRL pin is required for - Over temperature protection analog dimming. A digital signal with varying duty cycle AEC-Q100 Qualified on the PWM/EN pin will achieve PWM dimming. APPLICATIONS The IS32LT3957A is available in an eTSSOP-16 Automotive package with an exposed pad for enhanced thermal - Headlight dissipation. It operates from 5V to 75V over the - Daytime running light temperature range of -40C to +125C. - Fog light - Tail light Lumissil Microsystems www.lumissil.com 1 Rev. A, 03/06/2020 IS32LT3957A TYPICAL APPLICATION CIRCUIT V CC D 1 L 1 V OUT C OUT C IN 1 15 R O1 VCC GATE M 1 C VCC 13 CS 4.7 F 3 R O2 FAULTB R CS Optional 2 9 PWM/EN OVP 11 RPWM CPWM PWM ISP 1k 30pF R IS IS32LT3957A 6 COMP 10 16 ISN VDD RDIM 14 100 LED C C 8 CP VDD DIMOUT String R ICTRL ICTRL 220nF 1 F *Note 1 CSS 4 5 FRQSS R NTC SGND 12 7 RRT M 2 PGND RT/SYNC Figure 1 Typical Application Circuit (Boost Configuration) Figure 2 Typical Application Circuit (Buck-Boost Configuration) Lumissil Microsystems www.lumissil.com 2 Rev. A, 03/06/2020