NX2116/2116A/2116B/2117/2117A

4

Rev. 3.0

03/14/06

PIN DESCRIPTIONS

PIN SYMBOL

PIN DESCRIPTION

Power supply voltage. A high freq 1uF ceramic capacitor is placed as close as possible to

and connected to this pin and ground pin. The maximum rating of this pin is 5V.

This pin supplies voltage to high side FET driver. A high freq 0.1uF ceramic capacitor is

placed as close as possible to and connected to these pins and respected SW pins.

Ground pin.

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

output of the switching regulator to set the output DC voltage. When FB pin voltage is

lower than 0.6V, hiccup circuit starts to recycle the soft start circuit after 2048 switching

cycles.

This pin is connected to the drain of the external low side MOSFET via resistor and is the

input of the over current protection(OCP) comparator. An internal current source 40uA is

flown to the external resistor which sets the OCP voltage across the Rdson of the low side

MOSFET. Current limit point is this voltage divided by the Rds-on. Once this threshold is

reached the Hdrv and Ldrv pins are latched out.

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

driver. It is also used to hold the low side driver low until this pin is brought low by the

action of high side turning off. LDRV can only go high if SW is below 1V threshold .

High side gate driver output.

Low side gate driver output.

An open drain output that requires a pull up resistor to Vcc or a voltage lower than Vcc.

When FB pin reaches 90% of the reference voltage PGOOD transitions from LO to HI

state.

A resistor divider is connected from the respective switcher BUS voltages to these pins

that holds off the controller's soft start until this threshold is reached. An external low cost

Transistor can be connected to this pin for external enable control.

This pin is the output of error amplifier and is used to compensate the voltage control

feedback loop. This pin can also be used to perform a shutdown if pulled lower than 0.3V.

VCC

BST

GND

FB

OCP

SW

HDRV

LDRV

PGOOD

EN

COMP