400mA/800mA Synchronous Step-Down DC/DC with Average Input Current Limit

The LTC3619B is a dual monolithic synchronous buck regulator using a constant frequency current mode architecture.

The input supply voltage range is 2.5V to 5.5V, making it ideal for Li-Ion and USB powered applications. 100% duty cycle capability provides low dropout operation, extending the run time in battery-operated systems. Low output voltages are supported with the 0.6V feedback reference voltage. Channel 1 and channel 2 can supply 400mA and 800mA output current, respectively.

The LTC3619B’s programmable average input current limit is ideal for USB applications and for point-of-load power supplies because the LTC3619B’s limited input current will still allow its output to deliver high peak load currents without collapsing the input supply. When the sum of both channels’ currents exceeds the input current limit, channel 2 is current limited while channel 1 remains regulated. The operating frequency is internally set at 2.25MHz allowing the use of small surface mount inductors. Internal soft-start reduces in-rush current during start-up. The LTC3619B is available in small MSOP and 3mm × 3mm DFN packages. The LTC3619B is also available in a low quiescent current, high efficiency Burst Mode® version, LTC3619.

Light Load Operation

LTC3619

Low Ripple Burst Mode (<20mVpp), IQ < 50μA

LTC3619B

Pulse Skip (<5mVpp)

Applications

* High Peak Load Current Applications

* USB Powered Devices

* Supercapacitor Charging

* Radio Transmitters and Other Handheld Devices

* Programmable Average Input Current Limit: ±5% Accuracy

* Dual Step-Down Outputs: Up to 96% Efficiency

* Low Noise Pulse-Skipping Operation at Light Loads

* Input Voltage Range: 2.5V to 5.5V

* Output Voltage Range: 0.6V to 5V

* 2.25MHz Constant-Frequency Operation

* Power Good Output Voltage Monitor for Each Channel