PI1004-1 Datasheet, PDF (7/16 Pages) Vicor Corporation – Programmable Point-of-Load Controller with 6-bit VID

becomes the control reference. The amplifier EAIN
inverting input and the EAO output pin can be configured
as a unity gain follower or as an inverting amplifier with
the proper feedback components to set the close loop
gain and frequency response of the voltage control loop.
Differential sensing is accomplished by referencing the
entire PI1004 to the negative return of the load (typically
CPUVSS). The SGND pin serves a dual purpose of returning
the PI1004 VCC current and sensing the low side of the
load. The internal reference "rides" on SGND to
compensate for voltage changes at the load. Special care
must be taken in the layout to avoid noise pick-up or
offsets due to ground loop currents.
Fault Circuitry
There are three input conditions that will set the fault
latch determined by ENABLE, VIDOFF or UVLO states as
shown in Table 2. Any fault will clamp the non-inverting
error amp input (EAIP) and SS pin to SGND. The fault latch
is reset when the SS pin drops below 0.25 V AND all faults
are cleared at the Set dominant latch input.
Power Good and Over-Voltage Protection
The PWRGD and OVP (OVP in PI1004-2 only) pins provide
output signals when the output voltage exceeds internally
set thresholds. The inputs to the PWRGD and OVP
comparators are referenced to REFIN and VO. The PWRGD
and OVP signals are outputs for system use and do not
trigger an internal fault.
Programmable VID Offset
REFOUT is set to the VR10 maximum output voltage
according to Table 1. For PI1004-1, the no-load VID output
voltage can be reduced to accommodate various load line
tolerance bands with the OFFSET function. Once the value
of RAVP has been chosen for the desired load line,
ROFFSET can be selected for the required no-load offset.
Refer to Figure 4d to determine resistor values setting the
AVP and Offset parameters.
Figures 5-10 demonstrate some of the dynamic
performance of these functions such as AVP response
time, REFOUT response to VID change, VID blanking
interval, error amplifier unity gain slew rate and soft-start
response to stepped Vcc in that order. Figures 11-14
demonstrate typical DAC error performance at specific
temperatures and Figure 15 demonstrates the VID
performance from -55 to 125 degrees Celsius at VID=1.2V.
Picor Corporation • picorpower.com
Applications Description
The PI1004 products were developed to enable Vicor’s FPA
(Factorized Power Architecture) to meet Intel’s
requirements defined in VRM/VRD 10.X specifications. A
simplified schematic representation of this topology is
shown in Figure 4a. DC Performance data of this
configuration using the PI1004-1 is shown in Figures 16-17
and dynamic performance is shown in Figures 18a-g, 19a-b
and 20.
In addition to FPA applications, independent functions of
the PI1004 can be used in different combinations as
building blocks in control applications.
The PI-1004 can be used as a VID controlled reference in
an embedded power converter circuit. The PI1004 error
amp can be configured as a unity gain buffer to provide
the VRD capable reference to the non-inverting input to
the control amp. If AVP is required, a method for sensing
the load current would need to be implemented.
In isolated applications as shown in Figure 4b, the
reference and error amplifier might replace a TL431 (Vcc
power is required for the PI1004) while the PWRGD, OVP
and AVP blocks replace a quad comparator. The PI1004 is
a candidate for any application that uses a reference and
several amplifiers or comparators especially where digital
or hard-wire setting of voltages can be accommodated.
The IC can be used as a programmable reference control
for a converter or power supply with a positive reference
based trim configuration as shown in Figure 4c. For these
applications a programmable output voltage and over-
voltage features can be created using the error amp as a
buffer creating a VR10 reference for the SC/trim input of
the converter. Care must be taken not to exceed the
amplifier output sink and source current capabilities and
to be compatible with the converter reference pin.
The AVP block of circuits can be used to create two
independent voltage to current converters providing a
sink current that is the sum of the two at the IAVP pin.
Again consideration of the specified range for these
functions is required.
Finally the Power Good block can be used as basic
comparators for voltage monitoring with the addition of
an independent output on the OVP pin in the PI1004-2
An additional bit of resolution can be added to the DAC
by using the circuit shown in Figure 4d with proper
sequencing by the microprocessor 6.25 mV increments are
possible.
PI1004 Data Sheet Rev. 2.5 Page 7 of 16