Mar 29-07 RevD

SP6126: TSOT-6 PFET Buck Controller

 2007 Sipex Corporation

3

PIN DESCRIPTION

PIN #

PIN

NAME

DESCRIPTION

1

Input power supply for the controller. Place input decoupling capacitor as close

as possible to this pin.

2

GATE

Connect to the gate terminal of the external P-channel MOSFET.

3

VDR

Power supply for the internal driver. This voltage is internally regulated to

4

FB

Regulator feedback input. Connect to a resistive voltage-divider network to set

the output voltage. This pin can be also used for ON/OFF control. If this pin is

pulled above 1V the P-channel driver is disabled and controller resets internal

soft start circuit.

5

GND

Ground pin.

6

LX

This pin is used as a current limit input for the internal current limit comparator.

Connect to the drain pin of the external MOSFET through an optional resistor.

Internal threshold is pre-set to 300mV nominal and can be decreased by

changing the external resistor based on the following formula:

BLOCK DIAGRAM

FAULT

Register

Set Dominant

POR

ENBL

4-Bit counter

VDR

VIN

GATE

5V Internal LDO

VIN - 0.3V

Overcurrent

Comparator

LX

VDR

30uA

GND

5V

+

-

+

-

VREF

FAULT

FB

Oscillator

VIN

S

R

I = k x VIN

Error Amplifier

PWM Comparator

PWM Latch

Reset Dominant

Vin - 5V LDO

FAULT

+

-

1V

FAULT

200ms delay

UVLO

S

R

R