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Part Number: BQ24618
I'm still investigating, but it seems as though anytime I plug the battery in first I need to replace the Low-side NMOS. Is this something you have seen in the past?
Can you please show scope capture on the issue when damage occurs?
Application Engineer, Battery Charging Products
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In reply to Jing Zou:
In reply to JPAlleyne:
Cell count= 6
FET Voltage Rating = 40V
Here is the Schematic (we added the missing cap on SRP):
Well I haven't fully tested it but initial findings showed that there is the potential that the IC got damaged as well. You said that a large current would flow through the body diode of Q3 and then go to ground.
1) What path would it take to go to ground through Q3's body diode?
2) Is the voltage spike caused by the large current flowing through the inductor?
3) Is it the voltage spike that causes damage to components on the PH node?
4) What can I do to protect the circuitry right now, without major redesign?
Regarding 1, please see the path marked below.
Regarding 2, yes.
Regarding 3, I cannot conclude without look at scope captures.
Regarding 4, when battery is plugged in, the drain of the lowside mosfet rises fast which might bring up the gate voltage and cause damage. One solution is to add more capacitance at Cgs to hold gate voltage down. Or try to find a replacement of the low side FET which Cgd is less than Cgs.
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