Author Topic: CPLD Protection Diodes on JTAG Header - "R1" SMD MARKING  (Read 1152 times)

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Offline 2XTopic starter

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CPLD Protection Diodes on JTAG Header - "R1" SMD MARKING
« on: January 22, 2025, 10:37:38 pm »
Hello,
I have a CPLD where on the JTAG connector is connected an SMD chip with “R1” marking. Do you know what chip is this? I couldn’t find something with “R1” marking. Do you know what kind of chip can be this… it something standard that is connected on JTAG connector? I saw in the internet a design that have protection zener diodes at pins (TDI, TDO, TCK, TMS).


https://electronics.stackexchange.com/questions/546001/zener-diodes-for-jtag-interface




 

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Offline 2XTopic starter

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Re: CPLD Protection Diodes on JTAG Header - "R1" SMD MARKING
« Reply #2 on: January 22, 2025, 11:14:44 pm »
Thanks for your reply.
I can't find an SMD like this "ESDA5V3SC5" nowhere. If anyone have seen this marking "R1" and knows the part number... please tell me.
 

Offline ataradov

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Re: CPLD Protection Diodes on JTAG Header - "R1" SMD MARKING
« Reply #3 on: January 23, 2025, 12:42:26 am »
What do you mean you can't find it? DigiKey alone has 128,206  of them.

Why do you need that exact part? It is not really necessary in  first place, but if you want it, just place any TVS you can find in a compatible package.

Also, measuring TVS diodes with a multimeter is useless. They are used in reverse breakdown direction and multimeter usually don't provide enough voltage in diode mode. What you are observing is the forward voltage, which is fine. Your TVS is likely fine and does not need replacement.
« Last Edit: January 23, 2025, 01:00:37 am by ataradov »
Alex
 
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Offline 2XTopic starter

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Re: CPLD Protection Diodes on JTAG Header - "R1" SMD MARKING
« Reply #4 on: January 23, 2025, 07:38:05 am »
I don't want the exact same component and the component isn't faulty. Just from curiosity I would like to see what are the exactly specs of these TVS diodes because with multimeter I can't check the clamping voltage of the diodes. I use the multimeter just only to confirm that all the pins have the same value in order to have clue about what this component is. Thanks for your suggestions.
 


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