DS90UB933-Q1EVM: Why PoC design is different from 913A on EVM?

Yada,
sorry for confusion. yes, your understanding is correct. just to clarify:
1. both documents are correct.
2. the PoC filter performance of "FB + 4.7uF + 100uF" is better than "FB + 47uF". But both can work, especially for one more marginal high speed link design.

bet regards,
Steven

Steven,
Thank you.
Please tell me why both filters are OK.
1. The PoC filter of "FB + 4.7 uF + 100 uF" had a margin on the IC side.
2. There was a characteristic improvement in DS90UB913A and DS90UB933.
3. The Back Channel frequency is different between DS90UB913A and DS90UB933.
4. Other.

Best Regards,
chiaki

Hi, Chiaki,

what is your point here? regarding the PoC network, please visit www.ti.com/FPD-Link for the on-line video message to introduce PoC design.

basically, it includes two points: a. AC performance, the "FB+4.7uH+100uH" has better bandwidth performance than "FB+47uH", so the AC performance is better, but "FB+47uH" also can be accepted in the real application. b. DC design consideration.

for the diff. between UB913a and UB933, the key diff. is UB933 can support higher data rate when working at 12b HF mode. the back channel rate is dependent on the de-ser, both UB913a and UB933 can accept same back channel rate.





best regards,

Steven

Hi Steven,
I would like to know why there is no problem with both filters.
What is the backchannel transmission frequency of 913 and 933?

The Japan TI team got an explanation that the back channels of 913 and 933 are the same.
1. The impedance simulation result of the PoC filter was different.
2. The baud rate was different in the difference table.
3. It was said that 913 A filter can not be set to "FB + 47 uF".
I was very confused.

Since the back channel of 933 is transmitting at a higher frequency than 913, it was convinced if it got an explanation that the band used was shifted to the high range.

Best Regards,
chiaki

chiaki,
first of all, please note the link between UB913a or UB933 and the de-ser (in the other side) is high speed serial link design. when the PoC network is added to deliver the power over cable which is mixed with high speed signal together. To minimize the power transmission impact on the high speed signal, the PoC is designed. as mentioned above, the "FB + 4.7uH + 100uH" has better AC performance than "FB+47uH" PoC network, it means the high speed link has less reflection. but both PoC network design are qualified. from the performance viewpoint, the "FB+4.7uH+100uH" is recommended.
I think Japan TI team answer is correct, I re-answer as below:
1."FB+4.7uH + 100uH" has higher impedance, it means the link has less reflection and better AC performance, which is mentioned above.
2. the baud rate is same for UB913a and UB933.
3. both UB913a and UB933 can have same PoC network. dependent on the application and system condition, if the link has higher margin (such as lower PCLK freq., less PCLK noise), the "FB + 47uH" also is acceptable by both UB913a and UB933.

UB933 can support higher FC rate, but the data rate is dependent on the PCLK in the real application, also the back channel rate is decided by the de-ser device in the other side.
for example, if camera sensor PCLK is 70MHz@YUV422_8_8, both UB913a and UB933 must work at 980Mbps FC rate, and the back channel BC rate is ~4.5Mbps from the de-ser side.

best regards,
Steven

Hi Steven,
Thank you for your polite explanation.
If board area and cost allow, I would like to use "FB + 4.7 uH + 100 uH".
After all, there is a cost problem, we design a low price filter.
It is important to know the frequency used.

By the way, UB933 data sheet Electrical Characteristics has "Back Channel Frequency = 5.5 MHz" stated.
"Back channel data rate 2.75 to 3.3 Mbps at UB933 / UB934" is described in "ADAS Serializer and Deserializer Forward Channel and Back Channel Specification Comparison.pdf".
UB934 datasheet Back channel frequency select is stated as 00: 2.5 Mbps, 01: 1.5625 MHz.

Although the transmission frequency on the FC side is described as PCLK x 14, the frequency of the back channel is not stated.

From these documents, UB 933 back channel is shipping tested at 5.5 MHz. In design or evaluation it was 2.75 to 3.3 Mbps. When UB 933 --- UB 934 is connected, it transmits at 2.5 Mbps (5 MHz).
And I understood.

Best Regards,
chiaki

chiaki,
I think you are confused by back channel data rate...
actually regarding on the back channel rate, it has some variation:
1. when paired with diff. de-ser, the back channel data rate is different.
2. for the same de-ser., the back channel data rate also varied due to process / temperature change.
so, in general, you should understand it has some ranges, from ~2.5Mbps to ~5Mpbs. For your design, you can consider the bandwidth from ~2MHz, this can be accepted for the system design.

best regards,
Steven

Hi, Steven,
I thought the frequency of the back channel was fixed.
Is the process variation manufacturing variability?
In the case of UB933 / UB934, 47 uH can be used, but in the case of UB 933/UB 914 the low data rate so 47 u H can not be used.
Best Regards,
chiaki

Chiaki,
Yes, due to process and temperature, the oscillator would have some freq. variation.

1. for any combo among UB91x and UB93x, the "FB+4.7uH+100uH" is better. both PoC network can be used.
2. but as UB934 has better performance than UB914a, UB934 can be better to select "FB+47uH" compared with UB914a with the same PoC network.

To be simple, the answer can be "better" NOT "NOT be used".


Steven

Hi! Steven,

I select "FB + 47 uH" for UB933.
Thank you Steven.

Best Regards,
chiaki