I've a power supply using the LT3991. Nothing tricky, the component values are very close to matching those of the app notes.
Rt=75K, 18uH inductor, SSB44 diode, 220nF boost cap, 4.7+uF input, 66+uF output, 1.24M/499K feedback for 4.2V out, with 7.4V in.
En tied to Vin, BD tied to output.
Has been working fine on a number of prototypes (on Rev E... ), but now in production, some of the supplies won't start up! Some work fine.
The ones that work have no problem delivering 4.2V to about 1.5A. Perfect.
The ones that don't will output 4.2V, but act like a linear regulator. The output wont start up at all if there is more than 30mA load, and once
started, it can only source about 300mA. Again... no switching! I've rebuilt the whole supply with fresh components, and nothing. What the heck?
Anyone run into anything like this?
