Holtek Semiconductor Inc HT82P604B Datasheet
HT82P604B
Preliminary
Features
Operating voltage: 5V~12V
·
Drives two N-Channel MOSFETs
·
Simple single-loop control design
·
-
Voltage-mode PWM control
Fast transient response
·
-
High-bandwidth error amplifier
-
Full 0% to 100% duty ratio
Excellent output voltage regulation
·
-
±1% over line voltage and temperature
Applications
Power supply for PentiumTM, Pentium
·
Pro, PowerPCTMand AlphaTMMicroproces
sors
General Description
The HT82P604B provides complete control and
protection for a DC-DC converter optimized for
high performance microprocessor applications.
It is designed to drive two N-Channel
MOSFETs in a synchronous-rectified buck topology. The HT82P604B integrates all of the
control, output adjustment, monitoring and
protection functions into a single package.
The output voltage of the converter is easily adjusted and precisely regulated. The HT82P604B
includes a 5-input digital-to-analog converter
(DAC) that adjusts theoutput voltage from 2.1V
to 3.5V in 0.1V increments and from 1.3V to
2.05V in 0.05V steps. The precision reference
and voltage-mode regulator hold the selected
output voltage to within ±1% over temperature
andlinevoltagevariations.
The HT82P604B provides simple, single feed
back loop, voltage-mode control with fast tran
TM
DC-DC Converter
5 bit digital-to-analog output voltage selection
·
-
Wide range -1.3V to 3.5V
-
0.1V binary steps from 2.1V to 3.5V
-
0.05V binary steps from 1.3V to 2.05V
Power-good output voltage monitor
·
Over-voltage and over-current sensing ele
·
ment, uses MOSFET¢sr
Small converter size
·
-
Constant frequency operation
-
200kHz free-running oscillator program
mable from 50kHz to over 1MHz
High-power5Vto3.xVDC-DCregulators
·
-
Low-voltage distributed power supplies
·
sient response. It includes a 200kHz
free-running triangle-wave oscillator that is
adjustable from below 50kHz to over 1MHz.
The error amplifier features a 15MHz
gain-bandwidth product and 6V/ms slew rate
which enables high converter bandwidth for
fast transient performance. The resulting
PWM duty ratio ranges from 0% to 100%.
The HT82P604B monitors the output voltage
with a window comparator that tracks the DAC
output and issues a Power Good signal when
the output is within ±10%. The HT82P604B
protects against over-current conditions by in
hibiting PWM operation. Built-in over-voltage
protection triggers an external SCR to crowbar
the input supply. The HT82P604B monitors the
current by using the r
MOSFET which eliminates the need for a cur
rent sensing resistor.
-
DS (ON)
DS (ON)
-
-
-
of the upper
-
Pentium is a trademark of Intel Corporation
1 March 23, 2000
Preliminary
Pin Assignment
20
VSEN
OCSET
COM P
SS
VID0
VID1
VID2
VID3
VID4
FB
1
2
3
4
5
6
7
8
9
10
H T82P 604B
20 S O P
Pin Description
Pin No. Pin Name I/O Description
1 VSEN I
2 OCSET I
3SS O
4~8 VID0~4 I
9, 10 COMP, FB I
11 GND P
RT
19
OVP
VCC
18
17
LG A TE
16
PGND
BOO T
15
14
UGATE
PHASE
13
PGOOD
12
GND
11
This pin is connected to the converters output voltage. The
PGOOD and OVP comparator circuits use this signal to report
output voltage status and for overvoltage protection.
Connect a resistor (R
per MOSFET. R
(I
), and the upper MOSFET on-resistance (r
OCS
OCSET
) from this pin to the drain of the up
OCSET
, an internal 200mA current source
converter over-current (OC) trip point.
IR
´
I=
PEAK
OCS OCSET
r
DS(ON)
An over-current trip cycles the soft-start function.
Connect a capacitor from this pin to ground. This capacitor,
along with an internal 10mA current source, sets the soft-start
interval of the converter.
VID0-4 are the input pins to the 5-bit DAC. The states of these
five pins program the internal voltage reference (DACOUT).
The level of DACOUT sets the converter output voltage. It also
sets the PGOOD and OVP thresholds. Table 1 specifies
DACOUT for the 32 combinations of DAC inputs.
COMP and FB are the available external pins of the error ampli
fier. The FB pin is the inverting input of the error amplifier and
the COMP pin is the error amplifier output. These pins are used
to compensate the voltage-control feedback loop of the con
verter.
Signal ground for the IC. All voltage levels are measured with
respect to this pin.
HT82P604B
) set the
DS (ON)
-
-
-
2 March 23, 2000
Preliminary
Pin No. Pin Name I/O Description
PGOOD is an open collector output used to indicate the status of
the converter output voltage. This pin is pulled low when the
12 PGOOD O
13 PHASE O
14 UGATE O
15 BOOT I
16 PGND P
17 LGATE O
18 VCC P Provide a 12V bias supply for the chip to this pin.
19 OVP O
20 RT I
converter output is not within ±10% of the DACOUT reference
voltage. Exception to this behavivor is the ¢11111¢ VID pin com
bination which disables the converter; in this case, PGOOD as
serts a high level.
Connect the PHASE pin to the upper MOSFET source. This pin
is used to monitor the voltage drop across the MOSFET for
over-current protection. This pin also provides the return path
for the upper gate drive.
Connect UGATE to the upper MOSFET gate. This pin provides
the gate drive for the upper MOSFET.
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.
This is the power ground connection. Tie the lower MOSFET
source to this pin.
Connect LGATE to the lower MOSFET gate. This pin provides
the gate drive for the lower MOSFET.
The OVP pin can be used to drive an external SCR in the event
of an overvoltage condition.
This pin provides oscillator switching frequency adjustment. By
placing a resistor (R
200kHz switching frequency is increased.
F
» 200kHz +
S
R(k)
Conversely, connecting a pull-up resistor (R
VCC reduces the switching frequency.
» 200kHz +
F
S
R(k)
) from this pin to GND, the nominal
T
6
510
´
W
T
410
´
W
T
to GND)
(R
T
) from this pin to
T
7
(R
to 12V)
T
HT82P604B
-
-
Absolute Maximum Ratings
Supply Voltage ......................................... +15V
Input Voltage ............... GND-0.3 to V
CC
+0.3V
Note: These are stress ratings only. Stresses exceeding the range specified under ²Absolute Maxi
mum Ratings² may cause substantial damage to the device. Functional operation of this device
at other conditions beyond those listed in the specification is not implied and prolonged expo
sure to extreme conditions may affect device reliability.
Storage Temperature ............... -50°Cto125°C
Operating Temperature ............ -20°Cto75°C
3 March 23, 2000
-
-
Loading...