5

PGND (Pin 16)

This is the power ground connection. Tie the lower MOSFET

source to this pin.

LGATE (Pin 17)

Connect LGATE to the lower MOSFET gate. This pin

provides the gate drive for the lower MOSFET.

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:

RT pin has a constant voltage of 1.26V typically.

Functional Description

Initialization

The HIP6004E 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

supply voltages. The POR monitors the bias voltage at the VCC

current protection). The POR function initiates soft-start

operation after both input supply voltages exceed their POR

exceed the rising VCC threshold before POR initiates operation.

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

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). This

output voltage, the clamp on the reference input controls the

output voltage is in regulation. This method provides a rapid

and controlled output voltage rise. The PGOOD signal toggles

‘high’ when the output voltage (VSEN pin) is within

±10% of

DACOUT. The 2% hysteresis built into the power good

comparators prevents PGOOD oscillation due to nominal

output voltage ripple.

Overcurrent Protection

The overcurrent function protects the converter from a shorted

to monitor the current. This method enhances the converter’s

efficiency and reduces cost by eliminating a current sensing

resistor.

Fs

200kHz

5 x 10

6

R

()

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

+

≈

Fs

200kHz

4 x 10

7

R

()

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

–

≈

0V

0V

0V

TIME (5ms/DIV.)

SOFT-START

(1V/DIV.)

OUTPUT

(1V/DIV.)

VOLTAGE

PGOOD

(2V/DIV.)

FIGURE 3. SOFT START INTERVAL

HIP6004E