SN74CBTLV3257: Solution suggestion for JTAG level shifting

Ashwin srinivasan

Part Number: SN74CBTLV3257
Other Parts Discussed in Thread: TXB0104, SN74AXC8T245

Whether all the IO pins are Open collector? Since i have seen in the CBT data book, ten(enable time) its mentioned as Open collector for the mentioned part number.

I have connected the JTAG signal with 1.8V in the A port and 2.5V in the B1 and B2 ports just need to know whether thats fine or i need to level shifter ?

over 5 years ago

0 Adam Torma over 5 years ago

TI__Mastermind 45350 points

Ashwin,

The SN74CBTLV3257 is a passive FET switch that will connect the input directly to the output. If you have two different voltage domains you will need to use a level shifter device maybe like the TXB0104.

Thank you,

Adam

0 Ashwin srinivasan over 5 years ago in reply to Adam Torma

Prodigy 50 points

thank you adam, since we are using the JTAG signals with different voltage levels i have some concern about that. Thanks for clarification.

0 Karan Kotadia over 5 years ago in reply to Ashwin srinivasan

TI__Genius 16725 points

Hello Adam,

The TXB0104 might not be the best solution for you for a level shifter. This is an auto bidirectional level shifter with very little drive strength.
Based on your speed and bit requirements you can use our parametric search to find a level shifter that works best for you.
One possible device you can use is the SN74AXC8T245.

Thanks!
- Karan

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SN74CBTLV3257: Solution suggestion for JTAG level shifting