Suitable Electronics potentiometer

Hi Arumugam,

Do you want to use a digital pot to adjust the output voltage of the TPSM82822?

If so, what output voltage range do you need to achieve?  How much output current do you need?

Was there an image that was supposed to be in your first post?  It seems something did not upload correctly.

Hi Chris Glaser,

Yes i need to use digital pot to adjust the output voltage of the TPSM82822.

output voltages is 0.95V/2A , 0.75V/2A, 0.55V/2A & 2V/2A. I have re-attached document, Please let me know if your able to view.

Thanks and Regards,

Arumugam.p

Thank you for perfectly explaining.

We have the I2C-controlled TPS62864, but this comes in a WCSP package and does not support 2Vout.

You could do your method with the TPSM82822, but you cannot achieve the 0.55V since this is below the 0.6V FB pin voltage.

I would propose the method shown in figure 5 of this app note, with an I2C controlled DAC: https://www.ti.com/lit/an/slyt777/slyt777.pdf

This allows you to use the TPSM82822 power module and achieve all your required voltages.

Hi Chris Glaser,

As per requirement , Can we use digital Pot instead of DAC ? 

You have any thought on this, if Yes can you please specify few digital POT from TI.

Thanks and Regards,

Arumugam.P

Hi Chris Glaser,

Could you please help to understand little more. Thanks for understanding.

Thanks and Regards,

Arumugam.P

Hi Arumugam,

I reached out to the engineers who support our DACs and digipots.  In the meantime, let me address your two questions.

On page 5 of the app note, it says:

Figures 6 and 9 also show a hidden benefit of analog voltage margining: adding a voltage into the FB pin achieves output voltages below the converter’s FB pin voltage. The margining circuit shown in Figure 5 achieves a 0.3-V output voltage even with the TPS62088’s 0.6-V FB pin voltage...

Your figure with the TPSM82822 is drawn correctly.  There is an Excel calculator (reference 6 in the app note) that can compute the resistor values for each circuit.

For your question 1, try to do a KCL on the FB pin with and without the DAC circuit.  You cannot have Vout be below the FB voltage without a higher voltage injected into the circuit (by a DAC, for example).

For question 2, you can use the second tab in the spreadsheet in reference 6 to see what kind of output voltage range you get for a given DAC output voltage range.

Hi Chris,

Thanks for your support.

I would like to get the app note with Digital POT from TI to understand the working principles to control the output voltage in buck regulator.

could you please help me share your comments.

Note : Using DAC i understood we can adjust the output voltage. I want understand with digital pot to suit for my application.

Thanks and Regards,

Arumugam.P  

Hi,

As I understand from this thread, you want to do some kind of power supply margining right?

If yes, Please have a look at the application note describing the same using our new device DAC53608.

https://www.ti.com/lit/an/sbaa342a/sbaa342a.pdf?ts=1597059296811&ref_url=https%253A%252F%252Fwww.ti.com%252Fproduct%252FDAC53608

Also please see the below technote to understand the trade off using various methods.

https://www.ti.com/lit/an/slaa887/slaa887.pdf?ts=1597059336916&ref_url=https%253A%252F%252Fwww.ti.com%252Fproduct%252FDAC53401

Regards,

AK

Dear AK,

Your understanding is rite. Can i get app note with using Digital pot ?

Thanks and Regards,

Arumugam.P

Hi Arumugam,

We don't have any app note right now with digipot for power supply margining.

As such we are promoting our newer DAC's for power supply margining, since these are very easy to implement with DAC's rather than Digipot.

Let me know if you need help with the same.

Regards,

AK

Hi AK,

Thanks for your support.

I am looking for 1 channel DAC output with 3 address pins to support for more DAC's in the I2C address.

could you please help me on this and share the part number details.

Thanks and Regards

Arumugam.P

Hi Arumugam,

At this moment, we don't have any single channel I2C DAC with 3 address pins.

Regards,

AK

Dear Chris,

Sorry for late reply.

I am working with TPS62823DLCR & TPS62825DMQR to our design by using DAC121C081.

Please find analysis sheet and design calculation.

Could you please share your comments and confirm our analysis will work for TPS62823DLCR & TPS62825DMQR .

The design analysis have based on the app note https://www.ti.com/lit/an/slyt777/slyt777.pdf

Also please confirm, the hidden benefit is applicable for TPS62823DLCR & TPS62825DMQR to get 0.45V output by adjusting the FB pin like above app note.

Armstrong DC-DC converter study_20200817.pdf

Thanks and Regards,

Arumugam.P

Thanks AK.

Hi Arumugam,

Yes, this hidden benefit applies to those converters as well.

Your calculations look reasonable and correct.

Dear Chris,

Thanks for your support and confirming.

Can i get efficiency graph from 0.3V to 4V for TPS62823DLCR & TPS62825DMQR device.

I could not found in the datasheet also not able to analysis through WBdesign.

I will be happy if i get the efficiencies includes hidden benefits.

Thanks and Regards,

Axrumugam.P  

Hi Arumugam,

The D/S has efficiency curves for many output voltages.  You can use these as an estimate.  The FB pin margining circuit does not significantly impact the efficiency.

The actual inductor used and its characteristics also affects the efficiency.

It is best to order an EVM and test the margining circuit and measure the efficiency, using your actual components.

Hi Chris,

Thanks for your support.

Is it EVM available for TPS62823DLCR or TPS62825DMQR with output voltage control through DAC solution.

Thanks and Regards,

Arumugam.P

No, there is no EVM which is setup with the margining circuit.

And you can use the margining technique on the TPSM82822 as well and have a simpler solution with that power module.

Dear Chris,

Thanks for your support.

We are looking for LDO's (LDO4, LDO6, LDO7, LDO10, LDO11) to satisfy the below requirement along with External DAC to control the output voltage.

I am OK to have each voltage rail separate LDO's.

For Example : LDO7 

LDO Input Voltage : 0.95V (Buck output-2) 

LDO Output Voltage Typical : 0.85V 

LDO Output Voltage Min : 0.8075V

LDO Output Voltage Max : 0.8925V

LDO Output Current Typical : 150mA 

Thanks and Regards,

Arumugam.P

Hi Chris,

Thanks for your support.

could you please share your feedback.

Thanks and Regards,

Arumugam.P

Hello Chris,

Could you please share your comments.

Thanks and Regards,

Arumugam.P

Hello Arumugam,

Chris will be out until end of September and the last request you sent is about LDOs.

I will put you in contact with the LDO team.

Thanks,

Dorian

Thanks Dorian..

Can you please help and do the needful.

Dear Wilson,

Thanks for your support.    

I have already have the discussion with Mr. Dorian.

I am going to discuses and review my selection or schematics for my project with him.

Can you please don't resolve this ticket.

Thanks and Regards,

Arumugam.P