8-Bit Programmable 2- to 4-Phase
Synchronous Buck Controller
ADP3198
FUNCTIONAL BLOCK DIAGRAM
FEATURES
VCC
31
RT RAMPADJ
12 13
Selectable 2-, 3-, or 4-phase operation at up to
1 MHz per phase
11 ꢀV worst-case differential sensing error over
teꢀperature
SHUNT
REGULATOR
OSCILLATOR
19
30
29
28
OD
UVLO
SHUTDOWN
SET EN
RESET
Logic-level PWM outputs for interface to external high
power drivers
Enhanced PWM flex ꢀode for excellent load transient
perforꢀance
Active current balancing between all output phases
Built-in power-good/crowbar blanking supports on-the-fly
VID code changes
Digitally prograꢀꢀable 0.5 V to 1.6 V output supports both
VR10.x and VR11 specifications
Prograꢀꢀable short-circuit protection with prograꢀꢀable
latch-off delay
+
18
1
GND
EN
PWM1
PWM2
PWM3
CMP
–
–
+
850mV
+
RESET
CMP
–
DAC
+ 150mV
+
–
+
RESET
2/3/4-PHASE
DRIVER LOGIC
CMP
–
CSREF
27 PWM4
+
–
+
RESET
CMP
–
DAC
– 500mV
CURRENT
LIMIT
DELAY
2
PWRGD
CROWBAR
25
24
23
22
SW1
SW2
SW3
10
9
TTSENSE
VRHOT
THERMAL
THROTTLING
CONTROL
VRFAN
8
SW4
APPLICATIONS
Desktop PC power supplies for next generation
Intel® processors
17
15
CSCOMP
CSREF
11
7
ILIMIT
CURRENT
MEASUREMENT
AND LIMIT
+
–
DELAY
16
21
CSSUM
IMON
VRM ꢀodules
20
5
IREF
–
+
4
FB
COMP
+
GENERAL DESCRIPTION
PRECISION
REFERENCE
14
LLSET
–
BOOT
The ADP31981 is a highly efficient, multiphase, synchronous buck
switching regulator controller optimized for converting a 12 V
main supply into the core supply voltage required by high per-
formance Intel processors. It uses an internal 8-bit DAC to read
a voltage identification (VID) code directly from the processor,
which is used to set the output voltage between 0.5 V and 1.6 V.
3
FBRTN
VIDSEL
VOLTAGE
AND
6
SS
SOFT START
CONTROL
VID DAC
40
ADP3198
32
33
34
35
36
37
38
39
VID7 VID6 VID5 VID4 VID3 VID2 VID1 VID0
Figure 1.
This device uses a multimode PWM architecture to drive the
logic-level outputs at a programmable switching frequency that
can be optimized for VR size and efficiency. The phase relation-
ship of the output signals can be programmed to provide 2-, 3-,
or 4-phase operation, allowing for the construction of up to
four complementary buck switching stages.
The ADP3198 has a built-in shunt regulator that allows the part
to be connected to the 12 V system supply through a series resistor.
The ADP3198 is specified over the extended commercial
temperature range of 0°C to 85°C and is available in a
40-lead LFCSP.
The ADP3198 also includes programmable no load offset and
slope functions to adjust the output voltage as a function of the
load current, optimally positioning it for a system transient. The
ADP3198 also provides accurate and reliable short-circuit
protection, adjustable current limiting, and a delayed power-
good output that accommodates on-the-fly output voltage
changes requested by the CPU.
1 Protected by U.S. Patent Number 6,683,441; other patents pending.
Rev. A
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