TPS82085 lower VOUT possible?

LeonardEllis

Other Parts Discussed in Thread: LMZ31704, TPS82085, TPS62080, TPS82130

I have a design where the TPS82085 would be a perfect fit, however, I need the VOUT MIN to be 0.75V instead of the specified 0.80V. I looked at the LMZ31704, but it is at least 3x the pcb space of the TPS82085, so this will not work.

Is there a way to force the VOUT to the lower value, or, another device with a similar footprint that will achieve the 0.75V VOUT?

~Leonard

over 9 years ago

0 Anne Lu over 9 years ago

TI__Prodigy 50 points

Hi Leonard,

The core IP of this module only support down to 0.8V. Is module a must. we have discrete DCDC TPS62080 which can support down to 0.5V.

regards,

Anne

0 Chris Glaser over 9 years ago

TI__Guru**** 150830 points

What is the Vin and Iout needed?

The FB pin is regulated to 0.8V. This is why Vout is limited to 0.8V.

You can always bias FB such that a lower Vout is possible. Adding a higher voltage onto FB can do this. As an example, this is shown as Vctrl in this app note: www.ti.com/.../slva677.pdf

0 LeonardEllis over 9 years ago in reply to Anne Lu

TI__Guru 71526 points

We need the small 3x3mm footprint, all the discrete solutions I could come up with were 10x10mm, much too large for this design.

0 Anne Lu over 9 years ago in reply to Anne Lu

TI__Prodigy 50 points

TPS62080 comes in 2x2mm. What is the max current?

0 LeonardEllis over 9 years ago in reply to Anne Lu

TI__Guru 71526 points

approx. 2.9A

0 Chris Glaser over 9 years ago in reply to LeonardEllis

TI__Guru**** 150830 points

What is the Vin?

You can use the app note I sent earlier or maybe TPS82130 through its SS/TR pin.

0 LeonardEllis over 9 years ago in reply to Chris Glaser

TI__Guru 71526 points

Can the App Note be used with the TPS82085, or only the TPS82130? Finding out about VIN . .

0 Chris Glaser over 9 years ago in reply to LeonardEllis

TI__Guru**** 150830 points

Yes...

This is a generic circuit that can be used with virtually any IC.

Here is another app note which has more details: www.ti.com/.../slva471.pdf We need to know what they have in their system already which could be used to create the Vctrl signal.

Please let me know the usual stuff: customer, application, volumes, what they asked for, etc.

0 LeonardEllis over 9 years ago in reply to Chris Glaser

TI__Guru 71526 points

VIN is 3-3.3V. I have to find out if a DAC is available, and if not, there is no room to add one.

0 LeonardEllis over 9 years ago in reply to Chris Glaser

TI__Guru 71526 points

Actually, since we only need a 0.05V offset, I don't believe a DAC is required. Just a 0.05V source, this could be from a resistive divider, or a VREF device. The App Notes have the FB pin driven by a DAC, but that is only for making it adjustable. For our fixed application, a simple voltage source should work, correct?

0 Chris Glaser over 9 years ago in reply to LeonardEllis

TI__Guru**** 150830 points

As we discussed on the phone, you just need an analog voltage above the FB pin to obtain an output voltage below the FB pin's 0.8V voltage.

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TPS82085 lower VOUT possible?