LM3561

The LM3561 is a 2-MHz fixed-frequency current-mode synchronous boost converter. The device is designed to operate as a single 600-mA constant current driver for high-current white LEDs. The high-side current source allows for grounded cathode LED operation while the 250-mV regulated headroom voltage ensures that the LED current is well regulated and efficiency remains high.

The main features of the LM3561 include: an I²C-compatible interface for controlling the LED current, a hardware Flash enable input for direct triggering of the Flash pulse, dual TX inputs (TX1 and TX2) which force the Flash pulse into a low-current Torch mode during high battery current instances, an active high hardware enable (HWEN) allowing for fast hardware shutdown during system software failures, a dual mode pin which serves as either an indicator LED driver at up to 18mA or as a dedicated comparator input with an internal 1V reference, designed to monitor the voltage across a negative temperature coefficient thermistor (NTC), and a programmable input voltage monitor which monitors IN and can reduce the flash current or shutdown the device during low battery conditions.

Seven fault flags are available for read back over the I²C-compatible bus. These include: a flash timeout flag indicating the flash pulse has reached the end of the programmable timeout duration, a thermal shutdown flag indicating the LM3561's die temperature has exceeded 150°C, an LED fault flag indicating the output voltage has tripped the over-voltage threshold, or the LED has become shorted, TX1 and TX2 interrupt flags indicating if either of the TX inputs have been triggered, an NTC flag indicating the LED has experienced an over temperature condition, and a VIN Monitor flag indicating the input voltage has fallen below the VIN Monitor threshold.

The LM3561 is available in a tiny (1.215mm × 1.615mm × 0.6mm) 12-bump DSBGA and operates over the temperature range -40°C to +85°C.