HIP6014
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:
Fs ≈ 200kHz + R--5---T-•---(--1k---0-Ω---6--)
(RT to GND)
Conversely, connecting a pull-up resistor (RT) from this pin
to VCC reduces the switching frequency according to the
following equation:
Fs ≈ 200kHz – -R-4---T-•---(--1k---0-Ω---7--)
(RT to 12V)
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
10µA 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.
PGOOD
(2V/DIV.)
0V
SOFT-START
(1V/DIV.)
OUTPUT
VOLTAGE
(1V/DIV.)
0V
0V
t1
t2
t3
TIME (5ms/DIV.)
FIGURE 3. SOFT START INTERVAL
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 200µA 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
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