IS32LT3954-GRLA3-TR ISSI

IS32LT3954 CONSTANT-CURRENT 3-AMPERE PWM DIMMABLE BUCK REGULATOR LED DRIVER WITH OUTPUT FAULT REPORTING August 2019 GENERAL DESCRIPTION FEATURES The IS32LT3954 is a DC-to-DC switching converter Wide input voltage supply from 4.5V to 38V that integrates an N-channel MOSFET to operate in a - Withstand 40V load dump buck configuration. The device can operate from a True average output current control wide input voltage between 4.5V and 38V and 3A maximum output over operating temperature provides a constant current of up to 3A for driving a range single LED or multiple series connected LEDs. Cycle-by-cycle current limit The external resistor, R , is used to set a constant ISET Integrated high-side MOSFET switch LED output current, while allowing the output voltage Dimming via direct logic input or power supply to be automatically adjusted for a variety of LED voltage configurations. Internal control loop compensation The IS32LT3954 operates in a fixed frequency mode Under-voltage lockout (UVLO) and thermal during switching. There is an external resistor shutdown protection connected between the VCC and TON pins used to 2 A low power shutdown configure the on-time (switching frequency). The Spread spectrum to optimize EMI switching frequency is dithered for spread spectrum Robust fault protection and reporting function: operation which will spread the electromagnetic - Pin-to-GND short energy into a wider frequency band. This function is - Component open/short faults helpful for optimizing EMI performance. - Adjacent pin-to-pin short A logic input PWM signal applied to the enable (EN) - LED open/short pin will adjust the average LED current. The LED - Thermal shutdown brightness is proportional to the duty cycle of the AEC-Q100 Qualified PWM signal. APPLICATIONS True average output current operation is achieved with fast transient response by using cycle-by-cycle, Automotive and avionic lighting controlled on-time method. Daytime running lights The IS32LT3954 is available in an SOP-8-EP Turn/stop lights package with an exposed pad for enhanced thermal Front and rear fog lights dissipation. It operates from 4.5V to 38V over the Matrix headlight temperature range of -40C to +125C. Motorcycle headlight TYPICAL APPLICATION CIRCUIT Figure 1 Typical Application Circuit Lumissil Microsystems www.lumissil.com 1 Rev. D, 08/05/2019 IS32LT3954 PIN CONFIGURATION Package Pin Configuration (Top View) SOP-8-EP PIN DESCRIPTION No. Pin Description Power supply input. Connect a bypass capacitor C to ground. IN 1 VCC The path from C to GND and VCC pins should be as short as IN possible. On-time setting. Connect a resister from this pin to VCC pin to 2 TON set the regulator controlled on-time. Logic input for enable and PWM dimming. Pull up above 1.4V to 3 EN/PWM enable and below 0.4V to disable. Input a 100Hz~20kHz PWM signal to dim the LED brightness. Drive output current sense feedback. Set the output current by 4 FB connecting a resister from this pin to the ground. Open drain diagnostic pin. Active low to indicate fault 5 FAULTB conditions. 6 GND Ground. Internal MOSFET gate driver bootstrap. Connect a 0.1F X7R 7 BOOT ceramic capacitor from this pin to LX pin. Internal high-side MOSFET switch output. Connect this pin to 8 LX the inductor and Schottky diode. Thermal Pad Connect to GND. Lumissil Microsystems www.lumissil.com 2 Rev. D, 08/05/2019