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ADP2442 and ADIsimpower regarding question


I've used the ADP244x_Inverting_BuckBoostDesigner to generate a reference design for my application. I needed -12V output.

The ADIsimpower design tool worked perfectly fine (this time, finally). Anyway I have a question regarding the ADP2442. How can it produce negative velatge ranges? I see that in the design the negative voltage comes from the Power Ground pin. Another question is, why is there the output from the Vcc Pin connected to through one 1µF capacitor to the PGND pin and though J2 jumper to Sync/Mode pin?

To see exactly what I mean, this was the settings I've used for the reference design:

Vin (minimum): 15V

Vin (maximum) 16V

Vout: -12V

Iout: 0,2A=200mA

Design optimized for: Most efficient

Advanced settings:

Vout Ripple: 1%

Transient current step: 30%

Vout Transient error: 1%

Shield inductor: on

Output Filter: on

Switching frequency: 1000kHz

Thx and best regards.