Hello:
We fixed the MP6908 circuit VG uncertainty issue by dropping the output thru a zener, then feed it to TPS7A2450DBV LDO and there is no failure of the output ICs.
But the circuit started off and went into bursts of switching packets at the drain of lower NV6117.
Our circuit & routing mimics the UCC28782 EVAL kit. So what would cause the module to operate in bursts not steady-state?
It is as if some capacitor is not high enough to hold charge...such as at S13 node most likely?
Ours is .033uF while the Eval kit shows .022uF
..Could it be controller VDD , which has now 64 uF, X5R caps?
Of course, at this time we are not operating at 65W, much less. Our Rcs is .22 Ohm, ...Pl see attached exl file for this operating point.
At this time, xmfr is 20:4:4, Lpri is 380uH, lkg is <1 uH, electronic load is Resistive 20 Ohms or around this value.
We do not use a third coil to power MP6908 though.
Any helping hint to troubleshoot will be highly appreciated.EQ30PILOT_EXLCALCJUL27debug.xlsx
