ir3500a International Rectifier Corp., ir3500a Datasheet - Page 27

• Manufacturer Part Number: ir3500a
• Description: Xphase3 Vr11.0 & Amd Pvid Control Ic
• Manufacturer: International Rectifier Corp.

Open Daisy Chain Protection
IR3500A checks the daisy chain every time it powers up. It starts a daisy chain pulse on the PHSOUT pin and
detects the feedback at PHSIN pin. If no pulse comes back after 32 CLKOUT pulses, the pulse is restarted again. If
the pulse fails to come back the second time, the open daisy chain fault is registered, and SS/DEL is not allowed to
charge. The fault latch can only be reset by cycling the power to VCCL.
After powering up, the IR3500A monitors PHSIN pin for a phase input pulse equal or less than the number of
phases detected. If PHSIN pulse does not return within the number of phases in the converter, another pulse is
started on PHSOUT pin. If the second started PHSOUT pulse does not return on PHSIN, an open daisy chain fault
is registered.
Phase Number Determination
After a daisy chain pulse is started, the IR3500A checks the timing of the input pulse at PHSIN pin to determine the
phase number. This information is used to have symmetrical phase delay between phase switching without the
need of any external component.
Single Phase Operation
In an architecture where only a single phase is needed the switching frequency is determined by the clock
frequency.
Page 27 of 47
OV
THRESHOLD
OUTPUT
VOLTAGE
(VO)
VID
(FAST
VDAC)
VDAC
NORMAL
OPERATION
Figure 19 - Over-voltage protection during dynamic VID
VDAC
VID DOWN
50mV
LOW VID
50mV
VID UP
NORMAL
OPERATION
1.73V
VDAC + 130mV
July 3, 2008
IR3500A