ir3088a International Rectifier Corp., ir3088a Datasheet - Page 12

• Manufacturer Part Number: ir3088a
• Description: Xphase Ic With Fault And Overtemp Detect
• Manufacturer: International Rectifier Corp.

Phase Fault
It is possible for multiphase converters to appear to be working correctly with one or more phases not functioning.
The output voltage can still be regulated and the full load current may still be delivered. However, the remaining
phase(s) will be stressed far beyond their intended design limits and are likely to fail. Loss of a phase can occur due
to poor solder connections or mounting during the manufacturing process, or can occur in the field. The most
common failure mode of a buck converter is failure of the high side MOSFET. The IR3088A has the ability to detect if
a phase stops switching and can provide this information to the system through the PHSFLT output pin. If a phase
stops switching its output current will drop to zero and the output of its IR3088A current sense amplifier will be the
DACIN voltage. The Share Adjust Amplifier reacts to this by increasing the Ramp Slope Adjust current until it
exceeds the externally programmable PWM Ramp bias current. This will cause the voltage at the PWMRMP pin to
drop below its normal operating range. The Fault Comparator trips and drives the PHSFLT output to ground when
the voltage on the PWMRMP pin falls below 91% of the DACIN voltage. PHSFLT is an open-collector output and
should be pulled up to a voltage source through a resistor.
APPLICATIONS INFORMATION
Page 12 of 33
ENABLE
VID5
VID0
VID1
VID2
VID3
VID4
12V
1
2
3
4
5
6
7
OSCDS
VID5
VID0
VID1
VID2
VID3
VID4
IR3081A
CONTROL
IC
RVCC
10 ohm
CVCC
0.1uF
ROSC
Figure 7. IR3081A/3088A 12V to 2.5V 3 Phase Converter
EAOUT
OCSET
VBIAS
VDRP
ROCSET
BBFB
IIN
FB
RGATE
0.1uF
21
20
19
18
17
16
15
QGATE
RVDAC
CVDAC
DGATE
RBBFB
RDRP1
RBBDRP
RDRP
VGATE
RSHARE
CDRP
RFB21
CFB
RFB1
RCP
CCP1
RFB
RFB22
CCP
RBIASIN
RBIASIN
RBIASIN
1
2
3
4
5
1
2
3
4
5
1
2
3
4
5
CSCOMP
CSCOMP
CSCOMP
RMPIN+
RMPIN-
HOTSET
VRHOT
ISHARE
RMPIN+
RMPIN-
HOTSET
VRHOT
ISHARE
RMPIN+
RMPIN-
HOTSET
VRHOT
ISHARE
20k
20k
20k
IR3088A
PHASE
IC
IR3088A
PHASE
IC
IR3088A
PHASE
IC
GATEH
GATEH
GATEH
GATEL
GATEL
GATEL
VCCH
PGND
VCCH
PGND
VCCH
PGND
RCS-
CCS-
VCCL
RVCC
RPWMRMP
CVCC
RCS-
CCS-
VCCL
RVCC
RPWMRMP
CVCC
RCS-
CCS-
VCCL
RVCC
RPWMRMP
CVCC
15
14
13
12
11
15
14
13
12
11
15
14
13
12
11
CVCCL
CVCCL
CVCCL
CCS+
CCS+
CCS+
CBST
CBST
CBST
RCS+
RCS+
RCS+
DBST
L
DBST
L
DBST
L
CIN
CIN
CIN
DISTRIBUTION
IMPEDANCE
COUT
1/15
POWERGOOD
VRHOT
PHASE FAULT
VOUT SENSE+
VOUT+
VOUT-
VOUT SENSE-
IR3088A
/05