August 2014

DocID026819 Rev 1

1/4

For further information contact your local STMicroelectronics sales

office

www.st.com

STEVAL-ISA139V1

350 mA valley current limit adjustable step-down regulator based

on the PM6644

Data brief

Features



4.5 V to 25 V input voltage range



Fixed 3.43 V or adjustable 0.9 V to 5 V



Reference accuracy = +-1%, Tj=0 °C to

85 °C



380 mA maximum output current



Constant on-time control with current sense



Programmable switching frequency in PWM

mode



Pulse skipping mode (skip mode) at light

loads



Independent EN signal



Latched OVP and UVP



High accuracy 3.3 V reference voltage

Description

This product evaluation board is based on

STMicroelectronics' PM6644. The device

combines a 350 mA valley current limit step-down

regulator with a high accuracy 3.3 V voltage

reference in a small DFN10 3x3 package.

The switching regulator is based on a CoT

(constant on time) architecture that assures fast

load transient response. The embedded voltage

feed-forward provides nearly constant switching

frequency operation. Pulse-skipping is employed

to increase efficiency at very light load. The

switching frequency can be adjusted from 200

kHz to 600 kHz by means of a simple resistor.

The switching regulator can be programmed to

regulate a fixed value of 3.43 V or it can deliver

an adjustable voltage, depending on the FB pin

setup. The high precision integrated 3.3 V

reference can source up to 5 mA.