PGA308: 1W communication signal waveform

user6243139

Part Number: PGA308

Hi,

I checked a waveform about 1W communication signal.

Baud rate Jitter seems good (under 1% at User's Guide section 4.6, our baud rate is 111.11kbps).

But rise and fall time are so long (176ns/430ns). User's Guide section 4.6 shows about them under 0.5% for baud rate. Are there not good?

We put on a capacitor for the EMC test protection like a C3 of the Fig.5.6 at the User's Guide now. It may difficult to remove C.

If this waveform is not good, do you have any idea for this issue? We can change a baud rate more slow.

I tried to attach a waveforms and circuit. Can you see them?

Best regards,

KoT

over 5 years ago

0 kai klaas69 over 5 years ago

Guru 140200 points

Hi KoT,

to post a picture click the "Insert File" button (paper clip) in the header of text box.

Kai

0 user6243139 over 5 years ago in reply to kai klaas69

Prodigy 180 points

Hi Kai-san,

Thank you for your reply. I try again. Please confirm it.1W waveform.xlsx

Best regards,

Ko Tokoi

0 kai klaas69 over 5 years ago in reply to user6243139

Guru 140200 points

Hi Ko Tokoi,

yes, I can open it :-)

Kai

0 Luis Chioye over 5 years ago in reply to kai klaas69

TI__Guru 55466 points

HI Ko Tokoi,

As you have mentioned, at 111kbps, the 0.5% rise/fall time will be required per datasheet specification, and suspect the controller is having issues driving the EMC filter capacitance.

The USB-DAQ Platform controller used on the PGA308/9EVM has a discrete "One-Wire Speed-Up circuit" (described on section 3.7 on the USB DAQ Platform user Guide, link is below) to be able to cope with long lines and drive the large capacitance on the bus while supporting the baud rate. Please refer to section 3.7 of the USB DAQ user guide.

http://www.ti.com/lit/ug/sbou056/sbou056.pdf

In your case, would it be acceptable to reduce the baud rate to ~12kpps? Another option is to use a 1-wire bus accelerator/buffer/repeater to be able to drive the capacitance and support the high Baud rate.

Thanks and Regards,

Luis

0 user6243139 over 5 years ago in reply to Luis Chioye

Prodigy 180 points

Hi Luis-san,

Thank you for your reply and suggestion. We changed baud rate to 7.5kbps (include margin). It seems good.

I'd like to close this issue but I don't know how to close.

Best regards,

KoT

0 user6243139 over 5 years ago in reply to user6243139

Prodigy 180 points

I can see the "This resolved my issue" button

Best regards,

KoT

0 Luis Chioye over 5 years ago in reply to user6243139

TI__Guru 55466 points

HI Ko Tokoi,

Thank you very much for the update, glad this is working for you.

Kind Regards,

Luis

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PGA308: 1W communication signal waveform