TPS61178: VOUT tracking to VIN using FB pin

JCKK

Prodigy 20 points

Part Number: TPS61178

Hi there!

I'm interested in using TPS61178 to boost my PSU voltage.

One feature we'd like to implement is the TPS61178 VOUT tracking its VIN.

For example,

PSU VIN = 11V, VOUT = 15V
PSU VIN = 12V, VOUT = 16V
PSU VIN = 15V, VOUT = 19V

Is the TPS61178 capable of doing this if we have an external circuit connected to the FB pin?

We were thinking of using an a voltage divider on the PSU VIN and feed that into an voltage follower op amp circuit, then the output of that op amp would feed the FB pin of TPS61178.

Does TI have any experience with this kind of requirement? Any tips on implementation?

Thanks,

JCKK

over 1 year ago

0 Fergus He over 1 year ago

TI__Genius 11120 points

Hi JCKK,

The device is capable of this like using a external circuit connected to FB.

Please just ensure the input and output condition is within the device's spec.

Usually, we used an external signal connected to FB to control the output voltage in Audio usage.

you can use amp to implement this function.

Best Regards

Fergus

0 JCKK over 1 year ago in reply to Fergus He

Prodigy 20 points

Thank you for confirming functionality Fergus!

By chance, is there an equation or ratio on what voltage to inject into the FB to get specific output voltage?

Does TI have any reference design or internal design with TPS61178 that is doing something similar?

Appreciate your help :)

0 Eric Jia over 1 year ago in reply to JCKK

TI__Prodigy 215 points

Hi JCKK:

Here is a AN link for your reference. or you can download the power stage designer tool using the dynamic output voltage scaling function.

Hope this helps you.

thanks.

https://www.ti.com/lit/an/slvaej4/slvaej4.pdf?ts=1685934678187&ref_url=https%253A%252F%252Fwww.ti.com%252Fsitesearch%252Fen-us%252Fdocs%252Funiversalsearch.tsp%253FlangPref%253Den-US%2526searchTerm%253DSLVAEJ4%2526nr%253D7

0 JCKK over 1 year ago in reply to Eric Jia

Prodigy 20 points

Hi Eric,

I found this reference design that almost does what I'm looking for.

https://www.ti.com/tool/PMP15036

https://www.ti.com/lit/ug/tidudm1/tidudm1.pdf?ts=1686837143902

The reference design takes an audio signal and feeds it through op amps to manipulate the FB pin.

I tried simulating this design in PSPICE, but instead of having the audio signal portion, I removed it and just added a 200mV voltage source.

According to the reference design, a 200mV input to the tracking circuit should give me a boost output of 14V. Unfortunately I am not getting the same result (see attached PSPICE schematic and also waveform output).

I'm not very familiar with simulation tools, so maybe I'm doing something wrong? Could you help take a look at my simulation or provide a working one that matches the reference design?

I'm hoping to be able to match the PSPICE simulation with the reference design results, so I can then start to modify the simulation design for my use case.

TPS61178 PSPICE.pdf