IR3500VMPBF International Rectifier, IR3500VMPBF Datasheet - Page 20

• Manufacturer Part Number: IR3500VMPBF
• Description: The IR3500V Control IC combined with one or more xPhase3 Phase IC implement the control and MOSFET driver functions for a VR11.1 CPU VTT power supply.
• Manufacturer: International Rectifier

Specifications of IR3500VMPBF

• Package: 32-Lead MLPQ
• Circuit: X-Phase Control IC
• Switch Freq (khz): 250kHz to 1.5MHz
• Pbf: PbF Option Available

Pre-charging of converter output voltage may trigger OVP. If the converter output is pre-charged above 1.73V as
shown in Figure 17, the ROSC/OVP pin voltage will be higher than 1.6V when VCCLDRV voltage reaches 1.8V.
ROSC/OVP pin voltage will be VCCLDRV-1V and rise with VCCLDRV voltage until VCCL is above UVLO threshold,
after which ROSC/OVP pin voltage will be VCCL-1V. The converter cannot start unless the over voltage condition
stops and VCCL is cycled. If the converter output is pre-charged 130mV above VDAC but lower than 1.73V, as
shown in Figure 18, the converter will soft start until SS/DEL voltage is above 3.92V (4.0V-0.08V). Then, the over
voltage comparator is activated and fault latch is set.
During dynamic VID down, OVP could be triggered when output voltage can not follow VDAC voltage change at
light load with large output capacitance. Therefore, the over-voltage threshold is raised to 1.73V from VDAC+130mV
whenever dynamic VID is detected and the difference between output voltage and VDAC is more than 50mV, as
shown in Figure 19. The over-voltage threshold is changed back to VDAC+130mV if the difference is smaller than
50mV.
The overall system must be considered when designing for OVP. In many cases the over-current protection of the
AC-DC or DC-DC converter supplying the multiphase converter will be triggered and provide effective protection
without damage as long as all PCB traces and components are sized to handle the worst-case maximum current. If
this is not possible, a fuse can be added in the input supply to the multiphase converter.
(PHASE IC)
(PHASE IC)
OUTPUT
VOLTAGE
IIN
(ISHARE)
FAULT
LATCH
ERROR
AMPLIFIER
OUTPUT
(EAOUT)
GATEH
GATEL
(VO)
Page 20 of 34
VCCL-800 mV
VDAC
OVP
THRESHOLD
Figure 15 - Over-voltage protection during normal operation
NORMAL OPERATION
130mV
OVP CONDITION
July 28, 2008
IR3500V
AFTER
OVP