IS32LT3954A CONSTANT-CURRENT 3-AMPERE PWM DIMMABLE BUCK REGULATOR LED DRIVER WITH OUTPUT FAULT REPORTING April 2020 GENERAL DESCRIPTION FEATURES The IS32LT3954A 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 IS32LT3954A 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 Shared fault flag for multiple device operation to PWM signal. meet One-Fail-All-Fail True average output current operation is achieved AEC-Q100 Qualified with fast transient response by using cycle-by-cycle, controlled on-time method. APPLICATIONS In addition, IS32LT3954A integrates various fault Automotive and avionic lighting protections for robust operation. Detection of these Daytime running lights faults is reported by the FAULTB I/O pin. Multiple Turn/stop lights devices can have their FAULTB pins connected to Front and rear fog lights create a One-Fail-All-Fail system operation. Matrix headlight The IS32LT3954A is available in an SOP-8-EP Motorcycle headlight package with an exposed pad for enhanced thermal dissipation. It operates from 4.5V to 38V over the temperature range of -40C to +125C. Lumissil Microsystems www.lumissil.com 1 Rev. A, 04/09/2020 IS32LT3954A TYPICAL APPLICATION CIRCUIT Figure 1 Typical Application Circuit Figure 2 Typical Application Circuit (Several Devices In Parallel with FAULTB Interconnection) Lumissil Microsystems www.lumissil.com 2 Rev. A, 04/09/2020