TPS40210: FB voltage at Negative output

Part Number: TPS40210

Hi

Our customer are going to consider the configuration of the negative output from the negative input.　（Vin=-15V,Vo=-6.8V, Io=1.5A)

So, we found some reference design at TI site. At the one of design,we see the negative input-output configuration with TPS40210 such as PMP9624.

http://www.ti.com/jp/lit/df/tidrf59/tidrf59.pdf

I have some question regrading this configuration.

1. At this configuration, is TP3 is GND and TP4 is -3.3V ?

2. I understand FB voltage need to invert but how can we calculate the FB resister which is R102 and R2 and R7?

(Also EN signal need to invert.)

3.How can we calculate the inductor value and Switch current?

Could you give us if there is any other good references to help?

Best Regards,

Koji Hamamoto