RT9245B
Multi-Phase PWM Controller for K8 CPU Core Power Supply
General Description
RT9245B is a multi-phase buck DC/DC controller
integrated with all control functions for AMD K8 CPU. The
RT9245B could be operated with 2, 3 or 4 buck switching
stages operating in interleaved phase set automatically.
The multiphase 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.
RT9245B implements both voltage and current loops to
achieve good regulation, response and power stage
thermal balance.
RT9245B applies the DCR sensing technology newly. The
RT9245B extracts the ESR of output inductor as sense
component to deliver a precise load line regulation and
good thermal balance for next generation processor
application.
Current sense setting, droop tuning, V
CORE
initial offset
and ov er current protection are independent on
compensation circuit of voltage loop. The feature greatly
facilitates the flexibility of CPU power supply design and
tuning. The DAC output of RT9245B supports AMD K8
6-bit VID, precise offset value & smooth V
CORE
transient
at V
ID
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. The RT9245B comes to a small footprint
package TSSOP-28.
Features
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Multi-Phase Power Conversion with Automatic
Phase Selection
6-bit AMD K8 M2 DAC Output with Active Droop
Compensation for Fast Load Transient
Smooth V
CORE
Transition at VID Jump
Power Stage Thermal Balance by DCR 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
28-TSSOP Package
RoHS Compliant and 100% Lead (Pb)-Free
Applications
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AMD K8 Processors Voltage Regulator
Low Output Voltage, High Current DC-DC Converters
Voltage Regulator Modules
Pin Configurations
(TOP VIEW)
VID4
VID3
VID2
VID1
VID0
VID5
SGND
FB
COMP
PGOOD
DVD
SS
RT
VOSS
2
3
4
5
6
7
8
9
10
11
12
13
14
28
27
26
25
24
23
22
21
20
19
18
17
16
15
VCC
PWM1
PWM2
PWM3
PWM4
CSP4
CSP2
CSP3
CSP1
GND
ADJ
IOUT
CSN
IMAX
Ordering Information
RT9245B
Package Type
C : TSSOP-28
Operating Temperature Range
P : Pb Free with Commercial Standard
G : Green (Halogen Free with Commer-
cial Standard)
Note :
TSSOP-28
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.
DS9245B-02 March 2007
www.richtek.com
1
RT9245B
Functional Pin Description
VID4 (Pin 1), VID3 (Pin 2), VID2 (Pin 3), VID1 (Pin 4),
VID0 (Pin 5), VID5 (Pin 6)
DAC voltage identification inputs for K8. These pins are
internally pulled to 1.2V if left open.
SGND (Pin 7)
V
CORE
differential sense negative input.
FB (Pin 8)
Inverting input of the internal error amplifier.
COMP (Pin 9)
Output of the error amplifier and input of the PWM
comparator.
PGOOD (Pin 10)
Power good open-drain output.
DVD (Pin 11)
Programmable power UVLO detection input. Trip threshold
= 1.0V at V
DVD
rising.
SS (Pin 12)
Connect this SS pin to GND with a capacitor to set the
soft-start time interval.
RT (Pin 13)
Switching frequency setting. Connect this pin to GND with
a resistor to set the frequency.
VOSS (Pin 14)
V
CORE
initial value offset. Connect this pin to GND with a
resistor to set the negative offset value. Connect this pin
to VCC to set positive offset value.
IMAX (Pin 15)
Programmable over currert setting.
CSN (Pin 16)
Current sense negative input of all channels.
IOUT (Pin 17)
Output Current Indication Pin. The current through IOUT
pin is proportional to the output current.
ADJ (Pin 18)
Current sense output for active droop adjust. Connect a
resistor from this pin to GND to set the load droop.
GND (Pin 19)
Ground for the IC.
CSP1 (Pin 20), CSP2 (Pin 22), CSP3 (Pin 21) & CSP4
(Pin 23)
Current sense positive inputs for individual converter
channel current sense.
PWM1 (Pin 27), PWM2 (Pin 26), PWM3 (Pin 25) &
PWM4 (Pin 24)
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 high.
VCC (Pin 28)
IC power supply. Connect this pin to a 5V supply.
DS9245B-02 March 2007
www.richtek.com
3
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