hip6018cb Intersil Corporation, hip6018cb Datasheet - Page 7

• Manufacturer Part Number: hip6018cb
• Description: Advanced Pwm And Dual Linear Power Control
• Manufacturer: Intersil Corporation

VIN2 (Pin 12)
This pin supplies power to the internal regulator. Connect
this pin to a suitable 3.3V source.
Additionally, this pin is used to monitor the 3.3V supply. If,
following a startup cycle, the voltage drops below 2.05V
(typically), the chip shuts down. A new soft-start cycle is
initiated upon return of the 3.3V supply above the under-
voltage threshold.
Description
Operation
The HIP6018 monitors and precisely controls 4 output
voltage levels (Refer to Figures 1, 2, and 3). It is designed
for microprocessor computer applications with 3.3V and 5V
power, and 12V bias input from an ATX power supply. The
IC has one PWM controller, a linear controller, and a linear
regulator. The PWM controller is designed to regulate the
microprocessor core voltage (V
MOSFETs (Q1 and Q2) in a synchronous-rectified buck
converter configuration. The core voltage is regulated to a
level programmed by the 5-bit digital-to-analog converter
(DAC). An integrated linear regulator supplies the 2.5V clock
power (V
MOSFET (Q3) to supply the GTL bus power (V
Initialization
The HIP6018 automatically initializes upon receipt of input
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 (+12V
(+5V
pin. The normal level on OCSET1 is equal to +5V
fixed voltage drop (see over-current protection). The POR
function initiates soft-start operation after all three input supply
voltages exceed their POR thresholds.
Soft-Start
The POR function initiates the soft-start sequence. Initially,
the voltage on the SS pin rapidly increases to approximately
1V (this minimizes the soft-start interval). Then an internal
11µA current source charges an external capacitor (C
the SS pin to 4V. The PWM error amplifier reference input (+
terminal) and output (COMP1 pin) is clamped to a level
proportional to the SS pin voltage. As the SS pin voltage
slews from 1V to 4V, the output clamp generates PHASE
pulses of increasing width that charge the output
capacitor(s). After this initial stage, the reference input clamp
slows the output voltage rate-of-rise and provides a smooth
transition to the final set voltage. Additionally both linear
regulator’s reference inputs are clamped to a voltage
proportional to the SS pin voltage. This method provides a
rapid and controlled output voltage rise.
IN
) on the OCSET1 pin, and the 3.3V input on the VIN2
OUT2
). The linear controller drives an external
IN
) at the VCC pin, the 5V input voltage
230
OUT1
) by driving 2
OUT3
IN
less a
).
SS
) on
HIP6018
Figure 3 shows the soft-start sequence for the typical
application. At T0 the SS voltage rapidly increases to
approximately 1V. At T1, the SS pin and error amplifier
output voltage reach the valley of the oscillator’s triangle
wave. The oscillator’s triangular waveform is compared to
the clamped error amplifier output voltage. As the SS pin
voltage increases, the pulse-width on the PHASE pin
increases. The interval of increasing pulse-width continues
until each output reaches sufficient voltage to transfer
control to the input reference clamp. If we consider the 2.0V
output (V
the interval between T2 and T3, the error amplifier
reference ramps to the final value and the converter
regulates the output to a voltage proportional to the SS pin
voltage. At T3 the input clamp voltage exceeds the
reference voltage and the output voltage is in regulation.
The remaining outputs are also programmed to follow the
SS pin voltage. Each linear output (V
initially follows a ramp similar to that of the PWM output.
When each output reaches sufficient voltage the input
reference clamp slows the rate of output voltage rise. The
PGOOD signal toggles ‘high’ when all output voltage levels
have exceeded their under-voltage levels. See the Soft-Start
Interval section under Applications Guidelines for a
procedure to determine the soft-start interval.
Fault Protection
All three outputs are monitored and protected against
extreme overload. A sustained overload on any linear
0V
0V
0V
VOLTAGES
(0.5V/DIV)
OUTPUT
OUT1
T0
T1
SOFT-START
FIGURE 6. SOFT-START INTERVAL
) in Figure 3, this time occurs at T2. During
(2V/DIV)
PGOOD
(1V/DIV)
T2
TIME
T3
OUT2
and V
V
V
OUT1
V
OUT2
OUT3
(DAC = 2V)
OUT3
( = 2.5V)
( = 1.5V)
T4
)