RT9244
Multi-Phase PWM Controller for CPU Core Power Supply
General Description
The RT9244 is a multi-phase buck DC/DC controller
integrated with all control functions for GHz CPU VRM.
The RT9244 controls 2, 3 or 4 buck switching stages
operating in interleaved phase set automatically. The multi-
phase architecture provides high output current while
maintaining low power dissipation on power devices and
low stress on input and output capacitors. The high
equivalent operating frequency also reduces the component
dimension and the output voltage ripple in load transient.
RT9244 controls both voltage and current loops to achieve
good regulation, response & power stage thermal balance.
Precise current loop using R
DS(ON)
as sense component
builds precise load line for strict VRM DC & transient
specification and also ensures thermal balance of different
power stages. The settings of current sense, droop tuning,
V
CORE
initial offset and over current protection are
independent to compensation circuit of voltage loop. The
feature greatly facilitates the flexibility of CPU power supply
design and tuning.
The DAC output of RT9244 supports K8 CPU by 5-bit VID
input, precise initial value & smooth V
CORE
transient at VID
jump. The IC monitors the V
CORE
voltage for PGOOD and
over-voltage protection. Soft-start, over-current protection
and programmable under-voltage lockout are also provided
to assure the safety of microprocessor and power system.
Features
Multi-Phase Power Conversion with Automatic
Phase Selection
K8 DAC Output with Active Droop Compens-ation
for Fast Load Transient
Smooth V
CORE
Transition at VID Jump
Power Stage Thermal Balance by R
DS(ON)
Current
Sense
Hiccup Mode Over-Current Protection
Programmable Switching Frequency (50kHz to
400kHz per Phase), Under-Voltage Lockout and
Soft-Start
High Ripple Frequency Times Channel Number
RoHS Compliant and 100% Lead (Pb)-Free
Applications
AMD
®
Athlon
TM
64 and Opteron
TM
Processors Voltage
Regulator
Low Output Voltage, High Current DC-DC Converters
Voltage Regulator Modules
Pin Configurations
(TOP VIEW)
SS
OVP
VID4
VID3
VID2
VID1
VID0
VOSS
COMP
FB
ADJ
VDIF
VSEN
SGND
ISN4
ISN3
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
32
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
DVD
RT
PGOOD
PWM4
ISP4
ISP1
PWM1
PWM2
GND
ISP2
ISP3
PWM3
VCC
SS2
ISN1
ISN2
Ordering Information
RT9244
Package Type
S : SOP-32
Operating Temperature Range
P : Pb Free with Commercial Standard
G : Green (Halogen Free with Commer-
cial Standard)
Note :
RichTek Pb-free and Green products are :
RoHS compliant and compatible with the current require-
ments of IPC/JEDEC J-STD-020.
Suitable for use in SnPb or Pb-free soldering processes.
100%matte tin (Sn) plating.
DS9244-06 March 2007
SOP-32
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1
RT9244
Functional Pin Description
SS (Pin 1)
Connect this SS pin to GND with a capacitor to set the
start time interval. Pull this pin below 1V (ramp valley of
sawtooth wave in pulse width modulator) to shutdown the
converter output.
OVP (Pin 2)
Over voltage trip output.
VID4 (Pin 3), VID3 (Pin 4), VID2 (Pin 5), VID1 (Pin 6),
VID0 (Pin 7)
DAC voltage identification inputs for K8. These pins are
internally
pulled to 2.4V if left open.
VOSS (Pin 8)
V
CORE
initial value offset. Connect this pin to GND with a
resistor to set the offset value.
COMP (Pin 9)
Output of the error amplifier and input of the PWM
comparator.
FB (Pin 10)
Inverting input of the internal error amplifier.
ADJ (Pin 11)
Current sense output for active droop adjust. Connect a
resistor from this pin to GND to set the load droop.
VDIF (Pin 12)
V
CORE
differential sense output.
f
OSC
(kHz)
to GND with a capacitor to set the rising/falling time at VID
jump.
VCC (Pin 20)
IC power supply. Connect this pin to a 5V supply.
GND (Pin 21)
Ground for the IC.
PWM1 (Pin 26), PWM2 (Pin 25), PWM3 (Pin 21) &
PWM4 (Pin 29)
PWM outputs for each driven channel. Connect these pins
to the PWM input of the MOSFET driver. For systems
which use 3 channels, connect PWM4 high. Two channel
systems connect PWM3 and PWM4 high.
ISP1 (Pin 27), ISP2 (Pin 23), ISP3 (Pin 22) & ISP4
(Pin 28)
R
DS(ON)
current sense inputs for each individual converter
channel. Tie this pin to the component's sense node.
PGOOD (Pin 30)
Power good open-drain output.
RT (Pin 31)
Switching frequency setting. Connect this pin to GND with
a resistor to set the frequency.
450
400
350
300
250
200
150
100
50
Frequency vs. R
RT
VSEN (Pin 13)
V
CORE
differential sense positive input.
SGND (Pin 14)
V
CORE
differential sense negative input.
ISN1 (Pin 18), ISN2 (Pin 17), ISN3 (Pin 16) & ISN4
(Pin 15)
R
DS(ON)
current sense inputs from each individual converter
channel sense component's GND node.
SS2 (Pin 19)
DAC O/P ramping speed control for K8. Connect this pin
DS9244-06 March 2007
0
0
10
20
30
40
50
60
70
R
RT
(kΩ)
DVD (Pin 32)
Programmable power UVLO detection input. Trip threshold
= 2.0V at V
DVD
rising.
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