DS90UB936-Q1: DS90UB936-AC capacitor variation

Piotr F.

Hi Team,

What is the allowed AC capacitor value variation in DS90UB936-Q1 coax cable synchronous mode application, takin into account DC bias, temperature, initial tolerance etc?

Datasheet Table 228 gives some range, but comparing to datasheet Pin Functions Table (that gives only info that 100nf has to be used) it is not clear what is the minimum required effective capacitance (after temperature, DC and tolerance value de-rating).

Let me know!

Piotr

over 6 years ago

0 Casey McCrea over 6 years ago

TI__Guru** 103215 points

Hello Piotr,

We recommend +/-10% X7R 50V capacitors for the AC coupling. We do not explicitly have a spec for the minimum required effective capacitance.

Best Regards,

Casey

0 Piotr F. over 6 years ago in reply to Casey McCrea

TI__Intellectual 2950 points

The problem is that my customer cant find automotive-grade X7R 50V capaitors in 0402 package on the market.

Having minimum required effective capacitance they would be able to evaluate what other capacitors could be used.

How to tackle this topic?
Can you recommend automotive X7R 50V capaitors in 0402 ?

Or simply could they look at bigger packages (is this an issue for high speed trace)?

0 Casey McCrea over 6 years ago in reply to Piotr F.

TI__Guru** 103215 points

Hello Piotr,

Is the customer looking to implement PoC? If so then what voltage?

Best Regards,

Casey

0 Piotr F. over 6 years ago in reply to Casey McCrea

TI__Intellectual 2950 points

Hi Casey,

Yes, PoC is present. PoC voltage is 5V.

0603 caps will not fit on the PCB (no enough space), and 50V 100nF X7R 0402 caps are not available at my customer.
How to tackle it?

Piotr

0 Casey McCrea over 6 years ago in reply to Piotr F.

TI__Guru** 103215 points

Hello Piotr,

Since we don't have a defined criteria for this I would still suggest trying locate viable capacitors which match the original recommendation. With a quick search on Digikey I am able to find several viable options with immediate stock available:

https://www.digikey.com/product-detail/en/murata-electronics/GRM155R71H104KE14J/490-13342-2-ND/4905180

https://www.digikey.com/product-detail/en/taiyo-yuden/UMK105B7104KV-FR/587-3498-2-ND/4157221

https://www.digikey.com/product-detail/en/tdk-corporation/CGA2B3X7R1H104K050BB/445-6899-2-ND/2672792

Best Regards,

Casey

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DS90UB936-Q1: DS90UB936-AC capacitor variation