2-155

Functional Pin Description

RT (Pin 1)

This pin provides oscillator switching frequency adjustment.

200kHz switching frequency is increased according to the

following equation:

following equation.:

OCSET (Pin 2)

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

following equation:

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

SS (Pin 3)

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.

COMP (Pin 4) and FB (Pin 5)

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.

EN (Pin 6)

This pin is the open-collector enable pin. Pull this pin below

1V to disable the converter. In shutdown, the soft start pin is

discharged and the UGATE and LGATE pins are held low.

GND (Pin 7)

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

respect to this pin.

PHASE (Pin 8)

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 9)

Connect UGATE to the upper MOSFET gate. This pin

provides the gate drive for the upper MOSFET.

BOOT (Pin 10)

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.

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

80

70

60

50

40

30

20

10

0

SWITCHING FREQUENCY (kHz)

8

9

10

11

12

13

14

7

6

5

4

3

2

1

OCSET

SS

EN

COMP

FB

RT

VCC

LGATE

PGND

BOOT

UGATE

PHASE

GND

PVCC

Fs

200kHz

510

6

•

R

T

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

+

≈

Fs

200kHz

410

7

•

R

T

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

–

≈

I

PEAK

I

OCS

R

OCSET

•

r

DS ON

()

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=

HIP6012