TPS546C23: TPS546C23-Schematics Review (12V to 5V)

Sujith Mohandas

Part Number: TPS546C23

Dear Ti Team,

I have done a power design using TPS546C23 device with below mentioned requirement.I need to control the device through both PMBus and Hardware option.

Input Voltage=12V

Vout=5V

Iout=35A

Schematics:

/resized-image/__size/1549x0/__key/communityserver-discussions-components-files/196/TPS546C23_2D00_SCHEMATICS.PNG

Power calculator:

/cfs-file/__key/communityserver-discussions-components-files/196/TPS546C20A_5F00_TPS546C23_5F00_Calculator_5F00_Checklist_5F00_20122023.xlsx

I have attached the Schematics and updated excel sheet power calculator for review.Kindly request to you review my deisgn and let me know if there any update required.
I have few query listed below,

1) Regarding regulator output voltage settings ,during initial power up ,will this regulator will come up with output 5V using Hardware option resistor divider without setting any comments on PMbus?
2) I have selected feedback network values based on Webench tool,but in excel sheet recommneted feedback network values are not matching with webench tool values,Please give your input how can we proceeed further,Which is the correct values to be refered?
excell and webench comparison below :

/cfs-file/__key/communityserver-discussions-components-files/196/excell-and-Webenchtool.png

Thanks.,
Sujith M

over 1 year ago

0 Tahar Allag over 1 year ago

TI__Mastermind 32350 points

Hello Sujith,

The owner of the device is off for holidays. I assigned this to Joseph, he will provide his input next week.

Thanks

Tahar

0 Joseph Conrad over 1 year ago

TI__Expert 7860 points

Hi Sujith,

The Webench design is assuming that you are going to use PMBus to configure the output voltage using VOUT_COMMAND. This is why it gives a 1:3 ratio between RBIAS:R1, as it expects to use a VOUT_SCALE_LOOP of 0.25.

Since the default VOUT_SCALE_LOOP is 1 and default VOUT_COMMAND is 0.6V, you can consider the FB point as having a 0.6V reference. So in this case the calculator gives the correct values. I would use RBIAS=1.37kOhm and R1=10kOhm. You can update these in the spreadsheet, and also use the suggested values for the R2,R3, C1,C2,C3 values.

If you use these values for the resistor divider, it will allow you to start up at 5V without using PMBus to configure it further.

The other values in your design look good to me, just ensure that you update the compensation resistors and caps appropriately.

Thanks,

Joseph

0 Sujith Mohandas over 1 year ago in reply to Joseph Conrad

Prodigy 190 points

Hi Joseph,

Thanks for your inputs.I understand the difference between webench and excel tool.
Can you please have a look on the Feedforward capacitor requirement in my design? In excel tool only one column is showing yellow color which is f_LC ?
is this capacitor really required?

Please check the excel tool snaps
/cfs-file/__key/communityserver-discussions-components-files/196/pastedimage1703343548850v1.png

Regards,
Sujith M

0 Athos Zhao over 1 year ago in reply to Sujith Mohandas

TI__Expert 7320 points

Hi Sujith,

Our US team will reply you after the holiday.

0 Joseph Conrad over 1 year ago in reply to Sujith Mohandas

TI__Expert 7860 points

Hi Sujith,

I would follow the compensation calculations given for R1,2,3 and C1,2,3. I would recommend leaving a DNP (do not place) feedforward cap in case you find that you need to further tune the compensation.

Thanks,

Joseph

0 Sujith Mohandas over 1 year ago in reply to Joseph Conrad

Prodigy 190 points

Hi Joseph,

Could you please check the updated excel calculator and confirm, can i use these compensation and feedback values for my design.

I have a doubt on the compensation recommended value.In datasheet high frequency capacitor 100pF to 150pF is recommended between COMP to FB pins.But in excel calculator C3 recommended value is 34pF.
/cfs-file/__key/communityserver-discussions-components-files/196/pastedimage1704907506477v1.png

excel calculator:

/cfs-file/__key/communityserver-discussions-components-files/196/TPS546C20A_5F00_TPS546C23_5F00_Calculator_5F00_Checklist_5F00_10012024.xlsx

Thanks,
Sujith M

0 Joseph Conrad over 1 year ago in reply to Sujith Mohandas

TI__Expert 7860 points

Hi Sujith,

This is due to the input of the crossover frequency being too high. Try setting the FCO in the calculator between 40-45kHz.

Also, if you use a smaller number for R1 on line 98, 8000kOhm for example, then the recommended values will update and C3_rec will be higher also and around the 100pF value suggested in the datasheet.

Thanks,

Joseph

0 Sujith Mohandas over 1 year ago in reply to Joseph Conrad

Prodigy 190 points

Hi Jospeh,

Thanks for your inputs.

I have updated the power calculator and selected suitable Feedback and compensation network.
Please review the schematics and power calculator bode plots and provide if any review comments.
I would like to release the schematics for layouting.

/cfs-file/__key/communityserver-discussions-components-files/196/TPS546C20A_5F00_TPS546C23_5F00_Calculator_5F00_Checklist_5F00_23012024.xlsx

/resized-image/__size/3500x3500/__key/communityserver-discussions-components-files/196/TPS546C23_2D00_Schematics_2D00_23012024.png

Thanks for supporting.

Regards,
Sujith M

0 Joseph Conrad over 1 year ago in reply to Sujith Mohandas

TI__Expert 7860 points

Hi Sujith,

This looks good to me.

Thanks,

Joseph

0 Sujith Mohandas over 1 year ago in reply to Joseph Conrad

Prodigy 190 points

Hi Joseph,

I have a query on this device, during initial POWER UP i will be using hardware strap option for Vout settings. I would like to know if there any fault protection will interrupt the regulator output ? I will be following default register set value during initial power up.Please check and let me know if there any REG value needs to be changed before power ON the regulator?

/resized-image/__size/723x469/__key/communityserver-discussions-components-files/196/pastedimage1708534839410v2.png

Regards,
Sujith M

0 Joseph Conrad over 1 year ago in reply to Sujith Mohandas

TI__Expert 7860 points

Hi Sujith,

The UVP waits until soft-start is complete before it starts monitoring for a fault. All other faults are active during power-up.

The default settings should work fine to power on the device.

Thanks,

Joseph

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TPS546C23: TPS546C23-Schematics Review (12V to 5V)