[SOLVED] DC-DC converter to -3.3v

[clros]

Hi,

I need a DC-DC converter with a positive voltage input (+5V) and a negative voltage output (-3.3v) with a current minimum of 2A.

Can suggest me a circuit or a low cost Converter on a supplier or on ebay?

 

[FvM]

One possible solution is buck converter in inverting configuration, see e.g. https://www.ti.com/lit/an/snva022e/snva022e.pdf

 

[Akanimo]

Hi,

I need a DC-DC converter with a positive voltage input (+5V) and a negative voltage output (-3.3v) with a current minimum of 2A.

Can suggest me a circuit or a low cost Converter on a supplier or on ebay?

You need an inverting buck-boost. You could design it for 2.5V to 5V input range or so and -3.3V output.

That's all.

 

[KlausST]

Hi,

Or use a ready to buy isolating one. 5V to 3.3V.

Klaus

 

[BradtheRad]

Charge pump configured to invert polarity. Notice your 5V supply must provide several Amperes, if you wish to attach a 2A load.



Although diodes make for easier construction, they subtract from the output voltage. Instead transistors are suitable. Bias signals can be obtained from strategic points in the circuit.

The transistor marked '?' carries 90mA in an upward direction when it's supposed to be off. I tried to shut it off by taking bias voltage from various points. I tried a PNP type. It appears the only way to shut it off is by building a second clock signal.