NX2139A

5

Rev. 2.3

03/19/09

PIN DESCRIPTIONS

PIN NUMBER PIN SYMBOL

PIN DESCRIPTION

This pin is directly connected to the output of the switching regulator and

senses the VOUT voltage. An internal MOSFET discharges the output during

turn off.

This pin supplies the internal 5V bias circuit. A 1uF X7R ceramic capacitor is

placed as close as possible to this pin and ground pin.

This pin is the error amplifiers inverting input. This pin is connected via

resistor divider to the output of the switching regulator to set the output DC

voltage from 0.75V to 3.3V.

PGOOD indicator for switching regulator. It requires a pull up resistor to Vcc

or lower voltage. When FB pin reaches 90% of the reference voltage

PGOOD transitions from LO to HI state.

PGOOD indicator for LDO, requires a pull up resistor to Vcc or lower volt-

age. When LDOFB pin reaches 90% of the reference voltage PGOOD

transitions from LO to HI state.

This pin is the error amplifiers inverting input. This pin is connected via

resistor divider to the output of the LDO to set the output DC voltage.

The drive signal for external LDO N channel MOSFET.

Low side gate driver output.

Provide the voltage supply to the lower MOSFET drivers. Place a high

frequency decoupling capacitor 1uF X5R to this pin.

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

the input of over current protection(OCP) comparator. An internal current

source is flown to the external resistor which sets the OCP voltage across

the Rdson of the low side MOSFET.

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

the high side driver. It is also the input of zero current sensing comparator.

High side gate driver output.

This pin supplies voltage to high side FET driver. A high freq 1uF X7R

ceramic capacitor and 2.2ohm resistor in series are recommended to be

placed as close as possible to and connected to this pin and SW pin.

LDO enable input functions only when ENSW/MODE is not shutdown.

Switching converter enable input. Connect to VCC for PFM/Non synchronous

mode, connected to an external resistor divider equals to 70%VCC for ultra-

sonic, connected to GND for shutdown mode, floating or connected to 2V for

the synchronous mode.

VIN sensing input. A resistor connects from this pin to VIN will set the fre-

quency. A 1nF capacitor from this pin to GND is recommended to ensure the

proper operation.

Power ground.

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

PAD

VOUT

VCC

FB

PGOOD

LDOPG

LDOFB

LDODRV

LDRV

PVCC

OCSET

SW

HDRV

BST

ENLDO

ENSW/

MODE

TON

GND