TPS54618-Q1: Schematic Double Confirm

Kuan Wei Chen (Kevin Chen)

Genius 9710 points

Part Number: TPS54618-Q1

Dear Team,

Here is the schematic after checking with the customer.

Can you help on final review of four rails?

Kevin

over 4 years ago

0 JohnTucker over 4 years ago

TI__Guru**** 191445 points

Kevin,

How were the external components derived? Can you share the calculations? What are the design requirements? There are many possible valid solutions. If I back calculate them, most likely I will recommend changing all the components. Please share your deign details.

0 Kuan Wei Chen (Kevin Chen) over 4 years ago in reply to JohnTucker

TI__Genius 9710 points

Dear John,

Thanks for the reply.

What kind of the information you will need here?

I think all rail have Vin, Vout and Iout should be enough.

Kevin

0 JohnTucker over 4 years ago in reply to Kuan Wei Chen (Kevin Chen)

TI__Guru**** 191445 points

Kevin,

The designer used some method to derive each of the external component values. Can you share his equations? Did he use Webench? Can you share the file? Normally, if you share your work, I will review it in detail. If you just provide a schematic, I will look for obvious errors but otherwise will assume that the designer followed proper procedures. If I reverse engineer It, I will probably suggest them to change almost everything.

0 Kuan Wei Chen (Kevin Chen) over 4 years ago in reply to JohnTucker

TI__Genius 9710 points

Dear Tucker,

We just follow the Webench.

By different Vin, Vo, Io.

Kevin

0 JohnTucker over 4 years ago in reply to Kuan Wei Chen (Kevin Chen)

TI__Guru**** 191445 points

Kevin,

Can you forward orshare the we bench designs with me?

Thanks,

0 JohnTucker over 4 years ago in reply to JohnTucker

TI__Guru**** 191445 points

Kevin,

Thanks for forwarding the Webench designs. When using Webench, you have to follow their designs exactly. For example, your 1.2 V design uses 3 x 47 uF output capacitors. Webench design uses 2 x 10 uF, so the compensation only works for 2 x 10 uF, not 3 x 47 uF. That said, Webench like to design with the absolute minimum of output capacitance. I would not likely ever design a TPS54618-Q1 circuit with that low amount of output capacitance. You will need to rework all of these designs.

0 Kuan Wei Chen (Kevin Chen) over 4 years ago in reply to JohnTucker

TI__Genius 9710 points

Dear John,

I didn't understand your response here.

You ask me to follow the Webench's 2 x 10 uF suggestion, but you won't design with this low amount of output capacitance.

So what should I follow here?

I am confuse here.

Kevin

0 JohnTucker over 4 years ago in reply to Kuan Wei Chen (Kevin Chen)

TI__Guru**** 191445 points

Kevin,

If you use a Webench design, you must follow it exactly. Webench is biased towards lowest possible output capacitance in many cases. If you specify an output current that is much lower than the rated current (in this case you are using a 6 A device for a 1.5 A design) Webench may choose an out put capacitance that the experienced designer would deem too low. Remember power supply design is part art and part science. I think 3 x 47 uF is a solid choice for your designs. You would have to modify the Webench designs manually if it picks low output capacitance, then adjust the compensation as required. Another option would be to design all your circuits using 6 A as the output current. After the switch to HTML, Webench is no longer a very versatile design tool. You have to know how to work around it. Let me know if you need further assistance.

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TPS54618-Q1: Schematic Double Confirm