I am testing a 3-phase VRM. Appears to have a short
I req. some advice on replacement (if possible)
The VRM has an Intersil ISL6556B controller
This can drive up to 4 phases - this mobo has 3
The MOSFET drivers are a;
1 An Intersil HIP6601B and
2 An Intersil HIP6602B
The former package can drive 1 phase and the latter
can drive the other 2 phases.
I have 9 On Semiconductor NTD60N02R Power MOSFETs.
The Upper Gate on the HIPs drives three for the three phases
The Lower Gate on the HIPs drives six (from my inspection)
So this is an asymmetric topology for obvious reasons such as;
1. Reduces switching losses in the high-side FET and
2. Conduction losses in the low-side FET
at ratio of 2:1 (Low side to high side)
I did a quick check (in cct) of the FETs for shorts and the upper
side appear to be common to the gate and the sources are all
common to the phase on the HIP6601B.
As the FETs appear to be in good condition, I checked the drivers
to see if phase and the upper gate on each device for each phase were s/c.
I found on the HIP6601B, the upper gate drive was s/c to
the phase pin - this is the third phase. The lower gate was o/c.
On the HIP6602B, the upper gate 2 (phase 2) was s/c to the
the phase 2 pin. Lower gate 2 was o/c.
With the first phase on the HIP6602B, upper/lower were both o/c.
Am I right in stating the phase pin for each phase should be
common to the sources of the upper and lower FETs as is
typical with a multi-phase VRM?
As this was a quick analysis, and this board did get to POST
first time I tried it, would the fact, two of the upper phases
appear s/c impact this, or would, the apparent loss of two
phases of the upper FETs cause a failure to POST?
Of course, if I am correct, it may be either the driver or the
FETs (or both) are at fault. Would the replacement of the FET
drivers and the FETs be worthwhile?
A little history of this mobo tells a well known story (at least
in this forum). The system was powered by a Bestec and
the mobo was an apparent casualty.
The lytics appear ok. Have tested with an ESR meter.
Any help and insight appreciated.
I req. some advice on replacement (if possible)
The VRM has an Intersil ISL6556B controller
This can drive up to 4 phases - this mobo has 3
The MOSFET drivers are a;
1 An Intersil HIP6601B and
2 An Intersil HIP6602B
The former package can drive 1 phase and the latter
can drive the other 2 phases.
I have 9 On Semiconductor NTD60N02R Power MOSFETs.
The Upper Gate on the HIPs drives three for the three phases
The Lower Gate on the HIPs drives six (from my inspection)
So this is an asymmetric topology for obvious reasons such as;
1. Reduces switching losses in the high-side FET and
2. Conduction losses in the low-side FET
at ratio of 2:1 (Low side to high side)
I did a quick check (in cct) of the FETs for shorts and the upper
side appear to be common to the gate and the sources are all
common to the phase on the HIP6601B.
As the FETs appear to be in good condition, I checked the drivers
to see if phase and the upper gate on each device for each phase were s/c.
I found on the HIP6601B, the upper gate drive was s/c to
the phase pin - this is the third phase. The lower gate was o/c.
On the HIP6602B, the upper gate 2 (phase 2) was s/c to the
the phase 2 pin. Lower gate 2 was o/c.
With the first phase on the HIP6602B, upper/lower were both o/c.
Am I right in stating the phase pin for each phase should be
common to the sources of the upper and lower FETs as is
typical with a multi-phase VRM?
As this was a quick analysis, and this board did get to POST
first time I tried it, would the fact, two of the upper phases
appear s/c impact this, or would, the apparent loss of two
phases of the upper FETs cause a failure to POST?
Of course, if I am correct, it may be either the driver or the
FETs (or both) are at fault. Would the replacement of the FET
drivers and the FETs be worthwhile?
A little history of this mobo tells a well known story (at least
in this forum). The system was powered by a Bestec and
the mobo was an apparent casualty.
The lytics appear ok. Have tested with an ESR meter.
Any help and insight appreciated.
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