HIP6013CBZ datasheet(5/11 Pages) RENESAS

5 / 11 page

HIP6013

FN4325 Rev 1.00

Page 5 of 11

November 3, 2005

Functional Description

Initialization

The HIP6013 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 and the enable (EN) pin. 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). With the EN pin held to VCC, 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.

The Power-On Reset (POR) function inhibits operation with

the chip disabled (EN pin low). With both input supplies

above their POR thresholds, transitioning the EN pin high

initiates a soft start interval.

Soft Start

The POR function initiates the soft start sequence. An

internal 10

A 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 = 0.1F. 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 reference voltage and the

output voltage is in regulation. This method provides a rapid

and controlled output voltage rise.

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

A

(typical) current sink develops a voltage across ROCSET that

is reference 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 10

A 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 operation with an

overload condition. Note that the inductor current increases

to over 15A during the CSS charging interval and causes an

over-current trip. The converter dissipates very little power

with this method. The measured input power for the

conditions of Figure 4 is 2.5W.

TIME (5ms/DIV)

SOFT-START

(1V/DIV)

OUTPUT

(1V/DIV)

VOLTAGE

FIGURE 3. SOFT-START INTERVAL

HIP6013CBZ Datasheet(PDF) 5 Page - Renesas Technology Corp

HIP6013CBZ Datasheet(HTML) 5 Page - Renesas Technology Corp

Html Pages

1 2 3 4 5 6 7 8 9 10 11

Datasheet Download

Link URL