ISL6323B Datasheet, PDF (16/35 Pages) Intersil Corporation – Monolithic Dual PWM Hybrid Controller Powering AMD SVI Split-Plane and PVI Uniplane Processors

ISL6323B
PRE-PWROK METAL VID
Typical motherboard start-up occurs with the VFIXEN input
low. The controller decodes the SVC and SVD inputs to
determine the Pre-PWROK metal VID setting. Once the
POR circuitry is satisfied, the ISL6323B begins decoding the
inputs per Table 2. Once the EN input exceeds the rising
enable threshold, the ISL6323B saves the Pre-PWROK
metal VID value in an on-board holding register and passes
this target to the internal DAC circuitry.
TABLE 2. PRE-PWROK METAL VID CODES
SVC
SVD
OUTPUT VOLTAGE
(V)
0
0
1.1
0
1
1.0
1
0
0.9
1
1
0.8
The Pre-PWROK metal VID code is decoded and latched on
the rising edge of the enable signal. Once enabled, the
ISL6323B passes the Pre-PWROK metal VID code on to
internal DAC circuitry. The internal DAC circuitry begins to
ramp both the VDD and VDDNB planes to the decoded
Pre-PWROK metal VID output level. The digital soft-start
circuitry actually stair steps the internal reference to the
target gradually over a fix interval. The controlled ramp of
both output voltage planes reduces in-rush current during
the soft-start interval. At the end of the soft-start interval, the
VDDPWRGD output transitions high indicating both output
planes are within regulation limits
If the EN input falls below the enable falling threshold, the
ISL6323B ramps the internal reference voltage down to near
zero. The VDDPWRGD deasserts with the loss of enable.
The VDD and VDDNB planes will linearly decrease to near
zero.
TABLE 3. VFIXEN VID CODES
SVC
SVD
OUTPUT VOLTAGE
(V)
0
0
1.4
0
1
1.2
1
0
1.0
1
1
0.8
VFIX MODE
In VFIX Mode, the SVC, SVD and VFIXEN inputs are fixed
external to the controller through jumpers to either GND or
VDDIO. These inputs are not expected to change, but the
ISL6323B is designed to support the potential change of
state of these inputs. If VFIXEN is high, the IC decodes the
SVC and SVD states per Table 3.
Once enabled, the ISL6323B begins to soft-start both VDD
and VDDNB planes to the programmed VFIX level. The
internal soft-start circuitry slowly stair steps the reference up
to the target value and this results in a controlled ramp of the
power planes. Once soft-start has ended and both output
planes are within regulation limits, the VDDPWRGD pin
transitions high. If the EN input falls below the enable falling
threshold, then the controller ramps both VDD and VDDNB
down to near zero.
VCC
SVC
SVD
ENABLE
PWROK
VDD AND VDDNB
VDDPWRGD
VFIXEN
1
2
3
456
7
8
9 10
11
12
METAL_VID
V_SVI
METAL_VID
V_SVI
FIGURE 7. SVI INTERFACE TIMING DIAGRAM: TYPICAL PRE-PWROK METAL VID STAR-TUP
16
FN6879.0
March 23, 2009