Help Required. - -24V output required.

Manjunath

Use the TPS54260 device as an inverting power supply

http://focus.ti.com/docs/prod/folders/print/tps54260.html

Inverting Power supply Appnote

http://focus.ti.com/analog/docs/litabsmultiplefilelist.tsp?literatureNumber=slva317a&docCategoryId=1&familyId=751

Excel Sheet for inverting power supply, select TPS54260 from pull down menu

http://focus.ti.com/docs/toolsw/folders/print/swiftinv-calc.html

Regards,

David

Dear David,

Many thanks for your reply.

I had a look on your suggestions.

But, do you suggest me some thing like using an stadard linear regulator or any capacitor /diode combination circuit which could give me -24V @ 0.5A ?

When i go for swicther ,cost may be little high .

Is there any other simple solution whcih , straight away derives -24V out of +24V ?

thank you so much.

Best regards

Manjunath

Dear David,

I had a look into TPS54260.

I agree that using this device we can create -24V rail using available +24V rail.

Here I have another question ; If  I use this device ,  is it possible to use +24V and -24V simultaneously ? I am little skepticle about this ,since whcih is common reference point for  both +24V and -24V ?

The application requires ; +24V avalialable is also going to some load of 5A to some other circiutry, if i create -24v out of this using TPS54260 , can i use both +24V and -24V at a time? Whcih would be the common reference point for both +24v and -24V rail ? And Pin 9 ( GND) and Pin # 6 ( PWRGND) of the TPS54260 , where should i connect ?         -24V or to input ground. ?

please clarify. If i look into SLVA317a literature grounding scheme seems to be confusing,

please help. thanks.

You can use the +24 V rail both to power the TPS54260 inverting buck-boost and to supply additional +24 V loads.  For the other loads, the gnd return is the same as for +24 V.  For the inverting Buck Boost, the "GND" of the TPS54260 becomes the -24 V rail.  The local ground for that circuit is what would normally be the output voltage, i.e. the common point between the output inductor and the positive side of the output capacitor.

Dear John Tucker,

Thanks for the reply.  For inverting supply for TPS54260 ,  the pin numbers of the device , like  GND( Pin #9) , PWRGD( Pin # 6) , Thermal Pad ( Pin #11)  should be connected to Vout rail , that is -24V rail ?  In the data sheet  ( page #39 , Figure 63) or in apllication note slva317a ) all these pins are not shown .  please suggest  as my application needs both +24V and -24V supply rails to be loaded simultaneously. Is it possible to share your mail id ? so that i will share my circiutry and possible to review ? Please help.

Thanks

manjunath.madgeri@mindteck.com

Yes, the GND and thermal pad will be connected to the negative voltage rail.  The PWRGD output is the power good signal.  That does not need to be connected to groung or the negative rail.  For off forum assistance you should contact your local AFA or sales office.

some information is missing in Slva317b.pdf.

Would you please confirm the following pin connection:

For inverting power supply application, the Thermal Pad of TPS54260 (Pin # 11) should be connnected to GND(Pin #9). The PWRGD(Pin #6) and EN(Pin #3) should be left open.

Is it correct?

Thanks.

Hi Simon, yes this is correct. If you want to connect to the EN pin or PWRGD pin the signal needs to be level shifted to or from the IC's ground reference (the negative output voltage).

Regards,
Anthony