Preliminary
RT9238
VRM8.5 PWM and Triple Linear Power System Controller
General Description
The RT9238 is a 4-in-one power controller optimized
for high-performance microprocessor and computer
applications. The IC integrates a PWM controller,
triple linear controller as well as monitoring and
protection functions into a 28-pin SOP package. The
PWM controller regulates the microprocessor core
voltage with a synchronous buck converter. The first
linear controller supplies the computer system’s
AGTL+ 1.2V bus power. The second linear controller
provides power for the 1.5V AGP bus and the 3rd
linear controller provides 1.8V power for the chipset
core voltage and/or cache memory circuits.
The RT9238 features an Intel VRM8.5 compatible,
TTL 5-bit programmable DAC that adjusts the core
voltage from 1.090V to 1.865V in 25mV steps. The 5-
bit DAC has a typical
±1%
tolerance. The linear
regulators provide fixed output voltages of 1.2V
(V
OUT2
), 1.5V (V
OUT3
) and 1.8V (V
OUT4
) or user-
adjustable with an internal 1.265V reference. All the
three linear regulators drive external N-MOSFET or
NPNs bipolar for the pass transistor.
The RT9238 monitors all the output voltages. A
power-good signal is issued when the core voltage is
within
±10%
of the DAC setting and the other levels
are above their under-voltage levels. Additional build-
in over-voltage protection for the core output uses the
lower MOSFET to prevent output voltage above
115% of the DAC setting. The PWM over-current
function monitors the output current using the voltage
drop
across
the
MOSFET’s
R
DS(ON)
,
which
eliminates the need for a current sensing resistor.
Features
4-in-one Regulated Voltages for Microprocessor
Core, AGTL+ Bus, AGP Bus Power, and
North/South Bridge Core
Compatible with ISL6524
Power-good Output Voltage Monitor
Switching section
VRM8.5 TTL-Compatible 5-bit DAC
Programmable from 1.090V to 1.865V
±
1% DAC Accuracy
Fast Transient Response
VRM 8.5 Voltage Droop Tuning Uses MOSFET
R
DS(ON)
Fixed 200KHz Switching Frequency
Adaptive Non-overlapping Gate Driver
Over-current Monitor Uses MOSFET R
DS(ON)
Over-voltage Protection Uses Lower MOSFET
Linear Section
Fixed or User-adjustable Linear Regulator
Output Voltage
MOSFET and NPN Driving Capability
Ultra Fast Response Speed
Under-voltage Protection
Internal Thermal Shutdown
Pin Configurations
Part Number
RT9238CS
(Plastic SOP-28)
Pin Configurations
DRIVE2
FIX
VID3
VID2
1
2
3
4
5
28
27
26
25
24
23
22
21
20
19
18
17
16
15
VCC
UGATE1
PHASE1
LGATE1
PGND
OCSET1
FB1
VDAC
ICOMP
VSEN3
DRIVE3
GND
VAUX
DRIVE4
Applications
Motherboard Power Regulation for Computers
VID1
VID0
6
VID25
7
PGOOD
8
VTTPG
9
10
FAULT/VID4
VSEN2
11
SS24
12
SS13
13
VSEN4
14
DS9238-01 July 2001
www.richtek-ic.com.tw
1
Preliminary
Absolute Maximum Ratings
Supply Voltage
FAULT/VID4 and GATE Voltage
Input, Output or I/O Voltage
Ambient Temperature Range
Operating Junction Temperature Range
Storage Temperature Range
Lead Temperature (Soldering, 10 sec.)
Package Thermal Resistance
SOP-28,
θ
JA
60°C/W
+15V
RT9238
GND−0.3V ~ V
CC
+0.3V
GND−0.3V ~ 7V
0°C ~ +70°C
0°C ~ +125°C
−65°C
~ +150°C
300°C
Recommended Operating Conditions
Supply Voltage
Ambient Temperature Range
Junction Temperature Range
CAUTION:
Stresses beyond the ratings specified in “Absolute Maximum Ratings” may cause permanent damage to the
device. This is a stress only rating and operation of the device at these or any other conditions above those
indicated in the operational sections of this specification is not implied.
+12V±10%
0°C to 70°C
0°C to 125°C
Electrical Characteristics
(V
CC
= 12V, PGND = 0V, T
A
= 25°C, Unless otherwise specified.)
Parameter
VCC Supply Current
Nominal Supply Current
Power-On Reset
VCC Rising Threshold
VCC Falling Threshold
Rising VAUX Threshold
VAUX Threshold Hysteresis
Rising V
OCSET1
Threshold
DAC AND Band Gap Reference
DAC (VID25-VID3) Input Low Voltage
DAC(VID25-VID3) Input High Voltage
DACOUT Voltage Accuracy
Oscillator
Free Running Frequency
Ramp Amplitude
∆
V
OSC
180
--
200
1.9
225
--
KHz
V
P-P
VDAC + 40mV
--
2.0
-10
--
--
--
0.8
--
+20
V
V
mV
V
OCSET1
= 4.5V
V
OCSET1
= 4.5V
V
OCSET1
= 4.5V
V
OCSET1
= 4.5V
6.5
6
--
--
--
--
--
1.5
0.2
1.25
9.5
9
--
--
--
V
V
V
V
V
I
CC
UGATE1, LGATE1, DRIVE2,
DRIVE3, and DRIVE4 Open
--
10
--
mA
Symbol
Test Conditions
Min
Typ
Max
Units
To be continued
DS9238-01 July 2001
www.richtek-ic.com.tw
5
Test/Measurement
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