hip6007 Intersil Corporation, hip6007 Datasheet - Page 5

• Manufacturer Part Number: hip6007
• Description: Buck Pulse-width Modulator Pwm Controller
• Manufacturer: Intersil Corporation

Functional Description
Initialization
The HIP6007 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 (V
equal to V
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, V
+12V power source must exceed the rising V
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
10µA current source charges an external capacitor (C
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
C
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.
SS
= 0.1µF. Initially the clamp on the error amplifier (COMP
IN
IN
) on the OCSET pin. The level on OCSET is
less a fixed voltage drop (see over-current
IN
and V
135
CC
are equivalent and the
CC
threshold
SS
) on
HIP6007
Over-Current Protection
The over-current function protects the converter from a
shorted output by using the upper MOSFET’s on-resistance,
r
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 (R
programs the over-current trip level. An internal 200µA
(typical) current sink develops a voltage across R
is reference to V
MOSFET (also referenced to V
across R
start sequence. The soft-start function discharges C
a 10µA current sink and inhibits PWM operation. The soft-
start function recharges C
with the error amplifier clamped to the SS voltage. Should an
overload occur while recharging C
inhibits PWM operation while fully charging C
complete its cycle. Figure 4 shows this operation with an
overload condition. Note that the inductor current increases
to over 15A during the C
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.
DS(ON)
0V
0V
to monitor the current. This method enhances the
OCSET
FIGURE 3. SOFT-START INTERVAL
, the over-current function initiates a soft-
IN
SOFT-START
(1V/DIV)
. When the voltage across the upper
t1
SS
TIME (5ms/DIV)
SS
charging interval and causes an
, and PWM operation resumes
IN
t2
) exceeds the voltage
SS
OUTPUT
VOLTAGE
(1V/DIV)
, the soft start function
t3
SS
OCSET
to 4V to
SS
OCSET
with
that
)