I have successfully used a TPS82150's to generate +5V (approx 100mA) from +15V, and then a second TPS82150 to generate -5V from the +5V.
I then realised I needed to reduce the voltage of the both the +5V and -5V to +3.5V and -3.5V, so simply changed the potential divider into the FB pin.
From 10K (R4/R10) Low side / 55K3 (R1/R7)High side to 10K (R4/R10)low side / 33K2 (R1/R7) High Side.
I have attached the circuit.
The +5V reduces to +3.5V, as expected however the -ve rail is no longer being generated and is sitting at approx 300mV instead of -3V5.
I have tried two instances of the circuit, and bothe perform the same.
I suspect I am missing something simple...any suggestions welcome.
Giles