SN74LVT125-Q1: Quad Channel Buffer Recommendations for JTAG?

Jack Zhang

Part Number: SN74LVT125-Q1
Other Parts Discussed in Thread: SN74AC245-Q1, SN74LVC125A-Q1

Tool/software:

Hello, does TI have any quad channel buffers that can support a 4-wire JTAG interface (TDI, TDO, TCK, TMS)? Not sure there exists a part that can is bidirectional or has direction sensing. Signal logic level is 3.3V CMOS and data rate is typically10 MHz. 3-state outputs and high output drive capabilities are desired. Thanks for any help that can be provided!

4 months ago

0 Ian Graham 4 months ago

TI__Expert 7021 points

Hi Jack,

I'm going to recommend the SN74AC245-Q1. It's a bi-directional part that should support all of your spec requirements, but it is an 8 channel part.

Best,

Ian

+1 Clemens Ladisch 4 months ago

Guru 303080 points

As far as I know, all four JTAG signals are unidirectional, so you can simply use the SN74LVC125A-Q1.

0 Jack Zhang 4 months ago in reply to Clemens Ladisch

Intellectual 540 points

I believe you are right in that JTAG signals are not bidirectional, I will need to revisit that requirement on our design.

Any particularly reason why SN74LVC125A-Q1 might be be a more suitable choice than SN74LVC125A-Q1 for my application, since SN74LVC125A-Q1 has a lower average drive strength and longer average propagation delay?

0 Clemens Ladisch 4 months ago in reply to Jack Zhang

Guru 303080 points

At 3.3 V, LVC has better characteristics than AC.

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SN74LVT125-Q1: Quad Channel Buffer Recommendations for JTAG?