Using the LM5574 for Negative Output

In case it matters, I actually need to generate +/-15V from +24V to power split supply transducers.  Hence, the 24V Ground connection would also be the Ground return for both 15V supplies and Ground reference for the transducer.  The transducer generates a +/-5V which will go to an ADC (also referenced to the same Ground).

We are looking into the design. Will let back to you asap.

To convert the LM5574 EVM to inverting configuration, please refer to an application note: http://www.ti.com/lit/an/snva425a/snva425a.pdf

The idea is to connect Vout on the board as ground to the load and supply, connect the ground on the board to the negative side of the load, connect Vin to positive side of supply.

For +-15V, I think you could also consider using LM5017. One part could generate both + and - 15V in a fly buck configuration. Application note for this kind of circuit is http://www.ti.com/lit/an/snva674b/snva674b.pdf.

Sorry for the delay.

Yang

Hi Yang,

Thanks for the reply.

The LM5017 looks promising.  I did a Webench design using it and came up with the attached design.

Webench did not select some parts (Cout2, D1 and T1).  The cap and diode should be OK to find but the transformer is a concern as don't want to get into designing a custom part.  Could you recommend a part for T1?

Also, on a quick glance, the LM5017 isolated Eval board (as per AN-2204) looks like I should be able to configure it as required.  Would you agree?

I presume there is no problem using the isolated output as the -15V and referencing it to the GND of the Supply and +15V output.  The App Note shows the -15V to IGND and all others to GND.

Thanks,

Kieran

6114.CT Power Supply +24Vdc to +-15Vdc Supply Design using LM5017 (Webench Design 879849-27).pdf

Kieran,

I've forwarded your question to LM5017 expert.

Yang

Hi Vijay,

Thanks for the post.

Had a look at ref. design PMP7941.2.  Looks close to what I need so I guess I should be able to tailor it to suit.

Do you have any comments on the design I attached to my previous post (done via Webench)?

Any suggestions on a transformer for this design?

This is my first time to design such a circuit discretely so excuse my ignorance.  Would normally use a DC-DC module but cost is now a significant issue.

Thanks,

Kieran