ISSI IS31LT3954A

Description

The IS31LT3954A is a DC-to-DC switching converter that integrates an N-channel MOSFET to operate in a buck configuration. The device can operate from a wide input voltage between 4.5V and 38V and provides a constant current of up to 3A for driving a single LED or multiple series connected LEDs. The external resistor, RISET, is used to set a constant LED output current, while allowing the output voltage to be automatically adjusted for a variety of LED configurations. The IS31LT3954A operates in a fixed frequency mode during switching. There is an external resistor connected between the VCC and TON pins used to configure the on-time (switching frequency). The switching frequency is dithered for spread spectrum operation which will spread the electromagnetic energy into a wider frequency band. This function is helpful for optimizing EMI performance. A logic input PWM signal applied to the enable (EN) pin will adjust the average LED current. The LED brightness is proportional to the duty cycle of the PWM signal. True average output current operation is achieved with fast transient response by using cycle-by-cycle, controlled on-time method. In addition, IS31LT3954A integrates various fault protections for robust operation. Detection of these faults is reported by the FAULTB I/O pin. Multiple devices can have their FAULTB pins connected to create a “One-Fail-All-Fail” system operation. The IS31LT3954A is available in an SOP-8-EP package with an exposed pad for enhanced thermal dissipation. It operates from 4.5V to 38V over the temperature range of -40°C to +125°C.

Features

• Wide input voltage supply from 4.5V to 38V
  • Withstand 40V load dump
• True average output current control
• 3A maximum output over operating temperature range
• Cycle-by-cycle current limit
• Integrated high-side MOSFET switch
• Dimming via direct logic input or power supply voltage
• Internal control loop compensation
• Under-voltage lockout (UVLO) and thermal shutdown protection
• 2μA low power shutdown
• Spread spectrum to optimize EMI
• Robust fault protection and reporting function:
  • Pin-to-GND short
  • Component open/short faults
  • Adjacent pin-to-pin short
  • LED open/short
  • Thermal shutdown
• Shared fault flag for multiple device operation to meet “One-Fail-All-Fail”

Typical applications

• General high brightness LED lighting , Architecture lighting, Dimmable lights, Pool lighting

More information

• Datasheet
• IC product information