RT8857/A
4/3/2/1-Phase PWM Controller with Embedded Drivers
for CPU Core Power Supply
General Description
The RT8857/A is a 4/3/2/1-phase synchronous buck
controller with 2 integrated MOSFET drivers for Intel
VR11.1/VR10.x and AMD K8/K8_M2 CPUs power
application. RT8857/A uses differential inductor DCR
current sense to achieve phase current balance and active
voltage positioning. Other features include adjustable
operating frequency, adjustable soft start, power good
indication, external error-amp compensation, over voltage
protection, over current protection, VRHOT sensing and
IMON for various applications. RT8857/A comes to a small
footprint with WQFN-48L 7x7 package
Features
12V Power Supply Voltage
4/3/2/1-Phase Power Conversion
2 Embedded MOSFET Drivers
Internal Regulated 5V Output
VID table for INTEL VR11.1/VR10.x and AMD K8/
K8_M2 CPUs
Continuous Differential Inductor DCR Current Sense
Adjustable Soft Start
Adjustable Frequency
Power Good Indication
Adjustable Over Current Protection
Over Voltage Protection
VRHOT Sensing with External Thermistor
IMON Output Current Indication
Power State Indicator (PSI)
Support MOSFET Power Stage Input Voltage (V
IN
)
Down to 5V (RT8857A Only)
Small 48-Lead WQFN Package
RoHS Compliant and Halogen Free
Ordering Information
RT8857/A
Package Type
QW : WQFN-48L 7x7 (W-Type)
Lead Plating System
G : Green (Halogen Free and Pb Free)
Support V
IN
: 5/12V
Support V
IN
: 12V
Note :
V
IN
is the input voltage of MOSFET power stage.
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.
Richtek products are :
Pin Configurations
(TOP VIEW)
EN/VTT
36
35
34
33
32
31
30
29
28
49
27
26
25
13 14 15 16 17 18 19 20 21 22 23 24
VIDSEL
VOUT
VID0
VID1
VID2
VID3
VID4
VID5
VID6
48 47 46 45 44 43 42 41 40 39 38 37
Applications
Desktop CPU Core Power
Low Voltage, High Current DC/ DC Converter
FBRTN
QR1
QR2
SS/EN
COMP
FB
OFS
RT
ADJ
IMAX
IMAXPSI
IMONFB
VID7
PSI
1
2
3
4
5
6
7
8
9
10
11
12
GND
PWRGD
BOOT1
UGATE1
PHASE1
LGATE1
VCC12
LGATE2
PHASE2
UGATE2
BOOT2
PWM3
PWM4
ISP4
ISP3
ISP2
ISN4
ISN3
ISN2
ISN1
ISP1
WQFN-48L 7x7
DS8857/A-01 April 2011
VRHOT
www.richtek.com
1
VCC5
IMON
TSEN
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