
www.fairchildsemi.com
Pentium is a registered trademark of Intel Corporation. Programmable Active Droop is a trademark of Fairchild Semiconductor.
REV. 1.0.4 1/29/02
Features
Output programmable in 25mV steps from 1.05V to
1.825V using a dynamically programmable integrated
5-bit DAC
Controls adjustable linears for Vclock (2.5V),
Vnorthbridge (1.8V) or Vagp (selectable 1.5V/3.3V), and
Vadj (1.2V nominal)
Remote sense
Programmable Active Droop
Drives N-Channel MOSFETs
Overcurrent protection using MOSFET sensing
Overvoltage protection including startup
85% efficiency typical at full load
Integrated Power Good and Enable/Soft Start functions
Linears start instantly
Meets Intel VRM8.5 specifications using minimum
number of external components
24 pin SOIC package
up to 200mV
Applications
Power supply for Pentium
VRM for Pentium III processor
Programmable multi-output power supply
III Platforms
Description
The FAN5071 is a synchronous mode DC-DC controller IC
which provides a highly accurate, programmable set of output
voltages for multi-voltage platforms such as the Intel Pentium III,
and provides a complete solution for all Intel VRM8.5 CPU
applications, and for other high-performance processors. The
FAN5071 features remote voltage sensing, independently
adjustable current limit, and a proprietary wide-range Pro-
grammable Active Droop
for optimal converter transient
response and VRM8.5 compliance. The FAN5071 uses a 5-bit
D/A converter to dynamically program the output voltage dur-
ing operation from 1.05V to 1.825V in 25mV steps. The
FAN5071 uses a high level of integration to deliver load cur-
rents in excess of 28A from a 5V source with minimal exter-
nal circuitry. Synchronous-mode operation offers optimum
efficiency over the entire specified output voltage range. An
on-board precision low TC reference achieves 0.8% voltage
regulation without expensive external components. The
FAN5071 includes linear regulator controllers for Vclock
(2.5V),Vnorthbridge (1.8V) or Vagp (selectable 1.5V/3.3V),
and Vadjustable (1.2V nominal) each adjustable with an
external divider. The FAN5071 also offers integrated functions
including open-collector Power Good, Output Enable/Soft
Block Diagram
VID3
VID2
VID1
16
VID0
GNDP
23
22
2
18
24
1
17
-
+
-
+
OSC
1.24V
Reference
Digital
Control
Power
Good
5-Bit
DAC
VID4
8 7 6 5 4
+5V
+12V
PWRGD
-
+
ENABLE/SS
VCC
GNDA
3
LODRV
HIDRV
VCCP
21
VCCA
+5V
20
-
REF
REF
PWRGD,
OCL
PWRGD,
OCL
+3.3V
+1.2V/Adj
10
9
+2.5V
12
11
19
OCL
-
+
VCCP
PWRGD, OCL
V
3.3/1.5V
15
14
13
R
D
R
S
-
+
+
-
+
FAN5071
High Performance Programmable Synchronous
DC-DC Controller for Multi-Voltage Platforms