NX2142/2142A

4

Rev. 1.1

10/28/07

PIN DESCRIPTIONS

PIN SYMBOL

PIN DESCRIPTION

This pin supplies the internal 5V bias circuit. A 1uF high frequency ceramic X5R

capacitor must be placed as close as possible to this pin and ground pin to provide

high frequency bypass and to make the 5V regulator stable.

This pin supplies voltage to high side FET driver. A minimum 0.1uF ceramic high

frequency capacitor is placed as close as possible to and connected to this pin and

SW pin.

Power ground.

This pin is the error amplifiers inverting input. It is connected via resistor divider to

the output of the switching regulator to set the output DC voltage.

This pin is the output of the error amplifier and together with FB pin is used to compen-

sate the voltage control feedback loop. You can shutdown the switching regulator by

pulling this pin below 0.3V.

This pin is connected to source of high side FETs and provides return path for the

high side driver. This pin also provides input for the OCP comparator by sensing the

RDSON of the lower MOSFET. When this pin is below ground by 320mV, both drivers

are shutdown and enter hiccup mode.

High side gate driver output.

Low side gate driver output.

The output of the 5V regulator controller that drives a low current low cost external

bipolar transistor or an external MOSFET to regulate the voltage at Vcc pin derived

from bus voltage. This eliminates an otherwise external regulator needed in applica-

tions where 5V is not available. This regulator request a 1uF ceramic X5R type output

capacitor in order to be stable.

This pin provides the input voltage to the 5V regulator controller as well as the

oscillator for the PWM feed forward to work. When VIN exceeds 6V, the converter

starts to operate.

VCC

BST

GND

FB

COMP

SW

HDRV

LDRV

REGOUT

VIN