ADS1178: Synchronization by /SYNC was failed sometimes.

Kazuya Nakai59

Part Number: ADS1178

Hello guys,

One of my customers is evaluate ADS1178 on their own board.

They use 2 pcs of ADS1178 and these devices work with same CLK signal and this 2 device are synchronized by /SYNC pin.
But the synchronization sometimes failed.
At this moment, they have the following questions.
Could you please give me your reply?

Q1.
They know that the synchronization failure is happened by violation of setup/hold between CLK and /SYNC signal.
Is there any cause of the failure else?

Q2.
How much does /SYNC signal need wait to input after CLK signal started?

Your reply would be much appreciated.

Best regards,
Kazuya.

over 2 years ago

0 Keith Nicholas over 2 years ago

TI__Mastermind 48040 points

Hello Kazuya-san,

The ADS1178 should still synchronize if the CLK and /SYNC signals do not meet the timing requirements. However, they may not synchronize to the exact same clock edge, and you could expect 1 or 2 clock cycle difference between ADCs if this is the case. If /DRDY timing is different by more than 2 clock periods between the ADS1178 devices, then there is likely a different problem.

Q1. If the /SYNC signal has a lot of noise, or overshoot/ringing, then more than one edge could be interpreted, causing a failure to properly synchronize. A small RC filter may be helpful if this is the case.

Q2. After power-up of the ADC or after CLK has been started, you should wait until data are available, indicated by /DRDY going low. At this time, the synchronization pulse can be applied to the ADC.

Regards,
Keith Nicholas
Precision ADC Applications

0 Kazuya Nakai59 over 2 years ago in reply to Keith Nicholas

Guru 21805 points

Hello Keith,

Thank you very much for your reply and I'm sorry to be late my response.
Your reply is very helpful for us.

Thank you again and best regards,
Kazuya.

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ADS1178: Synchronization by /SYNC was failed sometimes.