Rail-to-rail step-down regulator sinks/sources ±5A from 0V to 14.5VOUT

August 17, 2016 // By Graham Prophet
LTC3623 is a ±5A high efficiency, current mode synchronous buck regulator that is adjustable from 14.5V down to 0V output with a single resistor. Its architecture uses a 50 µA current reference, combined with a single resistor, to set the output voltage.

The regulator’s design enables current sharing between multiple regulators, setting the output voltage for all of the regulators with a single external resistor. The LTC3623’s bipolar ±5A sink and source capability, wide VIN and VOUT capability, current mode control for tight line and load regulation, high efficiency, low external parts count and parallel capability suit it for multirail systems, in addition to tracking supplies, ASIC substrate biasing, DDR memory supplies, point-of-load power supplies, portable instruments, distributed power supply systems, battery-powered equipment and thermo-electric cooler systems.


The LTC3623’s 4V to 15V input voltage range is suitable for dual-cell Li-Ion applications, and fixed 5V and 12V intermediate bus systems. Low R DS(ON) integrated N-channel power MOSFETs (60mΩ top & 30 mΩ bottom) and synchronous rectification deliver efficiencies up to 96%. The device’s design allows dynamic adjustment of output voltage from 0V to V IN – 0.5V, offering virtually rail-to-rail performance. The LTC3623’s ability to sink up to 5A down to 0V OUT enables it to power down individual rails in the system as-needed. Its on-chip trimmed reference achieves high accuracy of ±1%. Output regulation and transient response are independent of output voltage. The user can directly drive the LTC3623’s I SET pin with an external voltage supply to program the converter’s V OUT. Output voltage tracking or soft-start is programmed via the I SET pin for applications that require power sequencing.


The regulator’s 400 kHz to 4 MHz switching capability enables the use of tiny, low cost capacitors and inductors, and combined with its compact QFN package, offers a very compact solution footprint for multirail applications. Additional device features include: programmable wire drop compensation, an input supply voltage regulation loop for extracting power from high impedance sources such as solar panels, an output current monitor, a power good voltage monitor, external synchronization capability and thermal protection. In shutdown it draws less than 1µA.


The LTC3623 is available in a