4

Functional Pin Description

OCSET (Pin 1)

the converter over-current (OC) trip point according to the

following equation:

An over-current trip cycles the soft-start function.

SS (Pin 2)

Connect a capacitor from this pin to ground. This capacitor,

along with an internal 10

µA current source, sets the soft-

start interval of the converter.

VID0-3 (Pins 3-6)

VID0-3 are the input pins to the 4-bit DAC. The states of

these four pins program the internal voltage reference

(DACOUT). The level of DACOUT sets the converter output

voltage. It also sets the PGOOD and OVP thresholds. Table

1 specifies DACOUT for the 16 combinations of DAC inputs.

COMP (Pin 7) and FB (Pin 8)

COMP and FB are the available external pins of the error

amplifier. The FB pin is the inverting input of the error

amplifier and the COMP pin is the error amplifier output.

These pins are used to compensate the voltage-control

feedback loop of the converter.

GND (Pin 9)

Signal ground for the IC. All voltage levels are measured with

respect to this pin.

PGOOD (Pin 10)

PGOOD is an open collector output used to indicate the

status of the converter output voltage. This pin is pulled low

when the converter output is not within

±10% of the

DACOUT reference voltage.

PHASE (Pin 11)

Connect the PHASE pin to the upper MOSFET source. This

pin is used to monitor the voltage drop across the MOSFET

for over-current protection. This pin also provides the return

path for the upper gate drive.

UGATE (Pin 12)

Connect UGATE to the upper MOSFET gate. This pin

provides the gate drive for the upper MOSFET.

BOOT (Pin 13)

This pin provides bias voltage to the upper MOSFET driver.

A bootstrap circuit may be used to create a BOOT voltage

suitable to drive a standard N-Channel MOSFET.

VCC (Pin 14)

Provide a 12V bias supply for the chip to this pin.

RT/OVP (Pin 15)

This pin is multiplexed, providing two functions. The first

function is oscillator switching frequency adjustment. By

Typical Performance Curves

FIGURE 2. BIAS SUPPLY CURRENT vs FREQUENCY

10

100

1000

SWITCHING FREQUENCY (kHz)

10

100

1000

TO +12V

100

200

300

400

500

600

700

800

900

1000

40

35

30

25

20

15

10

5

0

SWITCHING FREQUENCY (kHz)

14

15

16

9

13

12

11

10

1

2

3

4

5

7

6

8

OCSET

SS

VID0

VID1

VID2

VID3

FB

COMP

VSEN

VCC

BOOT

UGATE

PHASE

PGOOD

GND

RT/OVP

I

I

OCS

R

OCSET

•

r

DS ON

()

--------------------------------------------

HIP6008