HIP6014 datasheet(5/12 Pages) INTERSIL

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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.

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.

By placing a resistor (RT) from this pin to GND, the nominal

200kHz switching frequency is increased according to the

following equation:

Conversely, connecting a pull-up resistor (RT) from this pin

to VCC reduces the switching frequency according to the

following equation:

Functional Description

Initialization

The HIP6014 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 pin and the input voltage (VIN) on the

OCSET pin. The level on OCSET is equal to VIN less a ﬁxed

voltage drop (see over-current protection). The POR function

initiates soft start operation after both input supply voltages

exceed their POR thresholds. For operation with a single

+12V power source, VIN and VCC are equivalent and the

+12V power source must exceed the rising VCC threshold

before POR initiates operation.

Soft Start

The POR function initiates the soft start sequence. An internal

µA current source charges an external capacitor (CSS) on

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

CSS = 0.1µF. Initially the clamp on the error amplifier (COMP

pin) controls the converter’s output voltage. At t1 in Figure 3, 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). This

interval of increasing pulse width continues to t2. With sufficient

output voltage, the clamp on the reference input controls the

output voltage. This is the interval between t2 and t3 in Figure 3.

At t3 the SS voltage exceeds the DACOUT voltage and 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 ±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,

rDS(ON) to monitor the current. This method enhances the

converter’s efﬁciency and reduces cost by eliminating a

current sensing resistor.

The over-current function cycles the soft-start function in a

hiccup mode to provide fault protection. A resistor (ROCSET)

programs the over-current trip level. An internal 200

µA current

sink develops a voltage across ROCSET that is referenced to

VIN. When the voltage across the upper MOSFET (also

referenced to VIN) exceeds the voltage across ROCSET, the

over-current function initiates a soft-start sequence. The soft-

start function discharges CSS with a 10µA current sink and

inhibits PWM operation. The soft-start function recharges CSS,

and PWM operation resumes with the error amplifier clamped

to the SS voltage. Should an overload occur while recharging

CSS, the soft start function inhibits PWM operation while fully

charging CSS to 4V to complete its cycle. Figure 4 shows this

200kHz

510

•

T kΩ

()

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

≈

(RT to GND)

200kHz

410

•

T kΩ

()

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

–

≈

(RT to 12V)

TIME (5ms/DIV.)

SOFT-START

(1V/DIV.)

OUTPUT

(1V/DIV.)

VOLTAGE

PGOOD

(2V/DIV.)

FIGURE 3. SOFT START INTERVAL

HIP6014

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