HIP1012A

FN4419 Rev 6.00

Page 3 of 15

March 2004

Pin Descriptions

PIN #

SYMBOL

FUNCTION

DESCRIPTION

1

3V/12VS

3.3 V/12V Source

Connect to source of associated external N-Channel MOSFET switch to sense output

voltage.

2

3V/12VG

3.3V/12V Gate

Connect to the gate of associated N-Channel MOSFET switch. A capacitor from this node

to ground sets the turn-on ramp. At turn-on this capacitor will be charged to 17.4V by a 10

A

current source when in 5v/12V mode of operation, otherwise capacitor will be charged to

11.4V. A small resistor (10 - 200

) should be placed in series with the gate capacitor to

ground to prevent current oscillations.

Chip Supply

Connect to 12V supply. This can be either connected directly to the +12V rail supplying the

4

MODE/

PWRON1

Power ON/ Reset

Invokes 3.3V operation

PWRON1 and PWRON2 are used to turn-on and reset the chip. Both outputs turn-on when

either pin is driven low. After a current limit time out, the chip is reset by the rising edge of a

reset signal applied to either PWRON pin. Each input has 100

A pull up capability which is

compatible with 3V and 5V open drain and standard logic. PWRON1 is also used to invoke

3.3V control operation in preference to +12V control. By tying pin 4 to pin 3 the charge pump

is disabled and the UV threshold also shifts to 2.8V.

5PWRON2

Power ON/ Reset

6

5VG

5V Gate

Connect to the gate of the external 5V N-Channel MOSFET. A capacitor from this node to

ground sets the turn-on ramp. At turn-on this capacitor will be charged to 11.4V by a 10

A

current source. A small resistor (10 - 200

) should be placed in series with the gate

capacitor to ground to prevent current oscillations.

7

5VS

5V Source

Connect to the source side of 5V external N-Channel MOSFET switch to sense output

voltage.

8

5VISEN

5V Current Sense

Connect to the load side of the 5V sense resistor to measure the voltage drop across this

resistor between 5VS and 5VISEN pins.

9

PGOOD

Power Good indicator

Indicates that all output voltages are within specification. PGOOD is driven by an open drain

N-Channel MOSFET. It is pulled low when any output is not within specification.

10

Current Limit Timing

Capacitor

Connect a capacitor from this pin to ground. This capacitor controls the time between the

onset of current limit and chip shutdown (current limit time-out). The duration of current limit

time-out (in seconds) = 200k

11

Charge Pump

Capacitor

Connect a 0.1

when in 3.3V control mode.

12

GND

Chip Ground

13

Current Limit Set

Resistor

A resistor connected between this pin and ground determines the current level at which

14

3V/12VISEN

3.3V/12V Current Sense

Connect to the load side of sense resistor to measure the voltage drop across this resistor.