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BOOT (Pin 15)

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.

NC (Pin 16)

No connection.

NC (Pin 17)

No connection.

VCC (Pin 18)

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

OVP (Pin 19)

The OVP pin can be used to drive an external SCR in the

event of an overvoltage condition. Output rising 15% more

than the DAC-set voltage triggers a high output on this pin

and disables PWM gate drive circuitry.

RT (Pin 20)

This pin provides oscillator switching frequency adjustment.

200kHz switching frequency is increased according to the

following equation:

following equation:

Functional Description

Initialization

The HIP6005B automatically initializes upon receipt of power.

Special sequencing of the input supplies is not necessary. The

Power-On Reset (POR) function continually monitors the input

current protection). The POR function initiates soft start

operation after both input supply voltages exceed their POR

Soft Start

The POR function initiates the soft start sequence. An internal

10

the SS pin to 4V. Soft start clamps the error amplifier output

(COMP pin) and reference input (+ terminal of error amp) to

the SS pin voltage. Figure 3 shows the soft start interval with

the SS voltage reaches the valley of the oscillator’s triangle

wave. The oscillator’s triangular waveform is compared to the

ramping error amplifier voltage. This generates PHASE

pulses of increasing width that charge the output capacitor(s).

sufficient output voltage, the clamp on the reference input

voltage and the output voltage is in regulation. This method

provides a rapid and controlled output voltage rise. The

pin) is within

±5% of DACOUT. The 2% hysteresis built into

the power good comparators prevents PGOOD oscillation due

to nominal output voltage ripple.

Over-Current Protection

The over-current function protects the converter from a

shorted output by using the upper MOSFET’s on-resistance,

converter’s efficiency and reduces cost by eliminating a

current sensing resistor.

Fs

200kHz

5x10

6

R

()

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

+

≈

Fs

200kHz

4x10

7

R

()

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

–

≈

0V

0V

0V

TIME (5ms/DIV.)

SOFT-START

(1V/DIV.)

OUTPUT

(1V/DIV.)

VOLTAGE

PGOOD

(2V/DIV.)

FIGURE 3. SOFT START INTERVAL

0A

0V

TIME (20ms/DIV.)

5A

10A

15A

2V

4V

FIGURE 4. OVER-CURRENT OPERATION

HIP6005B