ISL6265 Datasheet, PDF (13/24 Pages) Intersil Corporation – Multi-Output Controller with Integrated MOSFET Drivers for AMD SVI Capable

ISL6265
threshold, the ISL6265 decodes and locks the decoded
value in an on-board hold register.
TABLE 1. 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 internal DAC circuitry begins to ramp Core and
Northbridge planes to the decoded pre-PWROK metal VID
output level. The digital soft-start circuitry ramps the internal
reference to the target gradually at a fixed rate of
approximately 2mV/µs. The controlled ramp of all output
voltage planes reduces in-rush current during the soft-start
interval. At the end of the soft-start interval, the PGOOD
output transitions high indicating all output planes are within
regulation limits.
If the EN input falls below the enable falling threshold, the
ISL6265 tri-states all outputs. PGOOD is pulled low with the
loss of EN. The Core and Northbridge planes will decay
based on output capacitance and load leakage resistance. If
bias to VCC falls below the POR level, the ISL6265
responds in the same manner previously described. Once
VCC and EN rise above their respective rising thresholds,
the internal DAC circuitry re-acquires a pre-PWROK metal
VID code and the controller soft-starts.
VFIX MODE
In VFIX Mode, the SVC and SVD levels fixed external to the
controller through jumpers to either GND or VDDIO. These
inputs are not expected to change. In VFIX mode, the IC
decodes the SVC and SVD states per Table 2.
TABLE 2. VFIXEN VID CODES
SVC
SVD
OUTPUT VOLTAGE (V)
0
0
1.4
0
1
1.2
1
0
1.0
1
1
0.8
Once enabled, the ISL6265 begins to soft-start both Core
and Northbridge planes to the programmed VFIX level. The
internal soft-start circuitry slowly ramps the reference up to
the target value. The same fixed internal rate of
approximately 2mV/µs results in a controlled ramp of the
power planes. Once soft-start has ended and all output
planes are within regulation limits, the PGOOD pin
transitions high.
In the same manner described in “Pre-PWROK Metal VID”
on page 12, the POR circuitry impacts the internal driver
operation and PGOOD status.
SVI MODE
Once the controller has successfully soft-started and
PGOOD transitions high, the processor can assert PWROK
to signal the ISL6265 to prepare for SVI commands. The
controller actively monitors the SVI interface for set VID
commands to move the plane voltages to start-up VID
values. Details of the SVI Bus protocol are provided in the
AMD Design Guide for Voltage Regulator Controllers
Accepting Serial VID Codes specification.
Once a set VID command is received, the ISL6265 decodes
the information to determine which output plane is affected
and the VID target required (see Table 3).The internal DAC
circuitry steps the required output plane voltage to the new
VID level. During this time, one or more of the planes could
be targeted. In the event either core voltage plane, VDD0 or
VDD1, is commanded to power-off by serial VID commands,
the PGOOD signal remains asserted. The Northbridge
voltage plane must remain active during this time.
If the PWROK input is de-asserted, then the controller steps
both Core and Northbridge planes back to the stored
pre-PWROK metal VID level in the holding register from
initial soft-start. No attempt is made to read the SVC and
SVD inputs during this time. If PWROK is reasserted, then
the on-board SVI interface waits for a set VID command.
If EN goes low during normal operation, all internal drivers
are tri-stated and PGOOD is pulled low. This event clears
the pre-PWROK metal VID code and forces the controller to
check SVC and SVD upon restart.
A POR event on VCC during normal operation will shutdown
all regulators and PGOOD is pulled low. The pre-PWROK
metal VID code is not retained.
VID-on-the-Fly Transition
Once PWROK is high, the ISL6265 detects this flag and
begins monitoring the SVC and SVD pins for SVI
instructions. The microprocessor will follow the protocol
outlined in the following sections to send instructions for
VID-on-the-Fly transitions. The ISL6265 decodes the
instruction and acknowledges the new VID code. For VID
codes higher than the current VID level, the ISL6265 begins
stepping the required regulator output(s) to the new VID
target with a typical slew rate of 7.5mV/µs, which meets the
AMD requirements.
When the VID codes are lower than the current VID level,
the ISL6265 begins stepping the regulator output to the new
VID target with a typical slew rate of -7.5mV/µs. Both Core
and NB regulators are always in CCM during a down VID
transition. The AMD requirements under these conditions do
not require the regulator to meet the minimum slew rate
specification of -5mV/µs. In either case, the slew rate is not
allowed to exceed 10mV/µs. The ISL6265 does not change
the state of PGOOD (VDDPWRGD in AMD specifications)
when a VID-on-the-fly transition occurs.
13
FN6599.1
May 13, 2009