L6738A

Device description and operation

Doc ID 18134 Rev 2

13/32

4

Device description and operation

The L6738A is a single-phase PWM controller with embedded high-current drivers that

provides complete control logic and protections to realize a general DC-DC step-down

converter. Designed to drive N-channel MOSFETs in a synchronous buck topology, with its

high level of integration, this 16-pin device allows a reduction of cost and size of the power

supply solution and also provides real-time PGOOD in a compact VFQFPN16 3x3 mm.

The L6738A is designed to operate from a 5 V or 12 V supply. The output voltage can be

precisely regulated to as low as 0.8 V with ±0.5% accuracy over line and temperature

variations. The controller performs remote GND recovery to prevent losses and GND drops

to affect the regulation.

The switching frequency is internally set to 200 kHz and adjustable through the OSC pin.

The IC can be disabled by pulling the OSC pin low.

The L6738A provides a simple control loop with a voltage-mode error-amplifier. The error-

amplifier features a 15 MHz gain-bandwidth product and 8 V/µs slew rate, allowing high

regulator bandwidth for fast transient response.

To avoid load damages, the L6738A provides overcurrent protection, and overvoltage and

undervoltage protection. The overcurrent trip threshold is monitored through the inductor

DCR, assuring optimum precision, saving the use of an expensive and space-consuming

sense resistor. The output voltage is monitored through the dedicated VSEN pin.

The L6738A implements soft-start by increasing the internal reference in closed loop

regulation. The low-side-less feature allows the device to perform the soft-start over pre-

biased output avoiding high current return through the output inductor and dangerous

negative spikes at the load side.

The L6738A is available in a compact VFQFN16 3x3 mm package with exposed pad.