I am troubleshooting an Enpirion EN63A0QI configured with VIN=6V, VOUT = 1.1V, and when placed under load supply output hovers at 0.7V (Measured at the RA resistor at the top of the VFB loop). Unloaded the VFB node sits at the correct 0.6V. Also when probing the circuit touching the scope probe to the VFB node causes the supply to rise to the configured voltage long enough for the POK signal to go high long enough to bring up the next supply in the power up sequence. Immediately after the next supply powers on VOUT goes to 0V and holds until power is removed and reapplied. For clarification the sequences power supplies are not drawing from the EN63A0QI, they just use its POK.
My question is first has anyone seen behavior similar to this for this supply, and based on the reaction to the scope probe is the failure to reach programmed voltage an instability in the VFB?
Values are set at RA = 294K, RB= 348K, R1=12K, CA = 15pF.
@JCaru
