ADS52J65: Input device for SYNC/SYSREF

Zhonghui Xu

Expert 5445 points

Part Number: ADS52J65
Other Parts Discussed in Thread: SN65LVDS047

Hi team,

We are evaluating the new board mounting with ADS52J65 now.

and we have two question below.

(1) Is it correct that we use SN65LVDS047 toward SYNC and SYSREF input of ADS52J65?

It looks like that the output voltage level of SN65LVDS047 and the input voltage level of ADS52J65 is not matched on each datasheet.

(2) The differential signal level is different from SYNC(475mVpp) and SYSREF(588mVpp).

And the VICM voltage level is different from SYNC(1.22Vdc) and SYSREF(0.975Vdc).

Is the voltage level correct??

If possible, please provide internal circuit interface.

ref(1)

SN65LVDS047 Datasheet(SLLS416B–JUNE 2000–REVISED DECEMBER 2003版)

ELECTRICAL CHARACTERISTICS (page3)

PARAMETER

TEST CONDITIONS

MIN

TYP

MAX

VOD

Differential output voltage

RL=100Ω

250

310

450

VOC(SS)

Input common-mode voltage

1.125

1.17

1.375

VOH

Output high voltage

1.33

1.5

VOL

Output low voltage

0.9

1.02

ADS52J65 Datasheet(SBAS783-DECEMBER 2018版)

6.7 Digital Characteristics (page11)

PARAMETER

CONDITIONS

MIN

TYP

MAX

DIGITAL INPUTS(LVDS):SYNC-P,SYNC-M,SYSREFP,SYSREFM

SYNC-

Input differential voltage

260

450

Input common-mode voltage

DC coupling required

1.2

1.4

SYSREF

Input differential voltage

300

450

Input common-mode voltage

DC c

Thank you very much for your help.

Best regards,

over 3 years ago

0 Bellala Kalyan over 3 years ago

TI__Intellectual 1590 points

Hi Zhonghui Xu,

Yes. the SN65LVDS047 would work well with ADS52J65. We generally see if the typical value of LVDS buffer output fits in the min-max range of ADS52J65. Could you please give more detail about your query 2 ?

The 475 mVpp for SYNC and 588 mVpp for SYSREF, are these measured voltages ? I couldn't find reference to these numbers in the datasheet. Same doubt for VICM voltages which you mentioned.

Regards,

Kalyan

0 Zhonghui Xu over 3 years ago in reply to Bellala Kalyan

TI__Expert 5445 points

Hi Kalyan,

Thank you for your feedback comment.

We wii use the SN65LVDS047 continuing.

About query 2, I attach the pdf file.
I would appreciate it if you could comment on anything.

thank you .

TI_ADS5265_input_interface.pdf

Best regards,

0 Zhonghui Xu over 3 years ago in reply to Bellala Kalyan

TI__Expert 5445 points

Hi Kalyan,

Thank you for your help.
is there any update.

Best regards,

0 Bellala Kalyan over 3 years ago in reply to Zhonghui Xu

TI__Intellectual 1590 points

Hi Zhonghui,

Thanks for sharing the issue in detail. The issue looks very peculiar. This kind of issues would occur when the input impedance offered by SYNCP/M reduces to smaller value. On how many devices did you checked ? Can you check the voltages by mounting different ADS52J65 chip. Also can you try measuring input impedance b/w P and M pins for SYNC and SYSREF ? input impedance can be checked with a multimeter.

Regards,

Kalyan

0 Zhonghui Xu over 3 years ago in reply to Bellala Kalyan

TI__Expert 5445 points

Hi Kalyan,

Thank you for your support.

I checked the input impedance on 2 differnt ADS52J65 chip.
The results of the input impedance b/w P and M pins for SYNC and SYSREF are shown below.

-SYNC P-M Impedance is 100 ohm with termination resistor(100ohm).
-SYNC P-M Impedance is 7K- 10K ohm without termination resistor(100ohm).

-SYSREF P-M Impedance is 100 ohm with termination resistor(100ohm).
-SYSREF P-M Impedance is 40K ohm without termination resistor(100ohm).

Thank you.

Best regards,

0 Bellala Kalyan over 3 years ago in reply to Zhonghui Xu

TI__Intellectual 1590 points

Hi Zhonghui,

Thanks for the update. Since ADS52J65 is under NDA restrictions we would like to take the discussion offline. Can you please drop a mail to support_us_afe_tx@list.ti.com with reference to this E2E post ? I'll keep this thread open until the issue resolved.

Regards,

Kalyan

0 Zhonghui Xu over 3 years ago in reply to Bellala Kalyan

TI__Expert 5445 points

Hi Kalyan,

Thank you for your time.

I have sent email,please help to reply.

Thanks a again.

Best regards,

0 Bellala Kalyan over 3 years ago in reply to Zhonghui Xu

TI__Intellectual 1590 points

Hi Zhonghui,

I'm closing this thread as we are directly supporting you via mail.

Regards,

Kalyan

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ADS52J65: Input device for SYNC/SYSREF