IR3508ZMPBF International Rectifier, IR3508ZMPBF Datasheet - Page 13

• Manufacturer Part Number: IR3508ZMPBF
• Description: The IR3508ZM Phase IC combined with any IR XPhase3 Control IC provides a full featured and flexible way to implement a power solution for the latest high performance CPUs and ASICs.
• Manufacturer: International Rectifier

Specifications of IR3508ZMPBF

• Package: 20-Lead MLPQ
• Circuit: X-Phase Phase IC
• Pbf: PbF Option Available

Emulated Bootstrap Diode
Over Voltage Protection (OVP)
The IR3508Z includes over-voltage protection that turns on the low side MOSFET to protect the load in the event of
a shorted high-side MOSFET, converter out of regulation, or connection of the converter output to an excessive
output voltage. As shown in Figure 7, if IOUT pin voltage is above V(VCCL) – 0.8V, which represents over-voltage
condition detected by control IC, the over-voltage latch is set. GATEL drives high and GATEH drives low. The OVP
circuit overrides the normal PWM operation and within approximately 150ns will fully turn-on the low side MOSFET,
which remains in conduction until IOUT drops below V(VCCL) – 0.8V when over voltage ends. The over voltage
fault is latched in control IC and can only be reset by cycling the power to control IC. The error amplifier output
(EAIN) is pulled down by control IC and will remain low. The lower MOSFETs alone can not clamp the output
voltage however a SCR or N-MOSFET could be triggered with the OVP output to prevent processor damage.
Operation at Higher Output Voltage
The proper operation of the phase IC is ensured for output voltage up to 5.1V. Similarly, the minimum VCC for
proper operation of the phase IC is 8 V. Operating below this minimum voltage, the current sharing performance of
the phase IC is affected.
IOUT(ISHARE)
IR3508Z integrates a PFET to emulate the bootstrap diode. If two or more top MOSFETs are to be driven at higher
(PHASE IC)
(PHASE IC)
switching frequency, an external bootstrap diode connected from VCCL pin to BOOST pin may be needed.
OUTPUT
VOLTAGE
FAULT
LATCH
ERROR
AMPLIFIER
OUTPUT
(EAOUT)
GATEH
GATEL
(VO)
Page 13 of 19
VCCL-800 mV
VDAC
OVP
THRESHOLD
Figure 7: Over-voltage protection waveforms
NORMAL OPERATION
130mV
OVP CONDITION
Jan 09, 2009
IR3508Z
AFTER
OVP