CDC3RL02: Back feeding and 2 devices in parallel

Sam460

Part Number: CDC3RL02

We're using the device to allow us to choose between two clock sources (i.e 2 instances of the CDC3RL02). This means that two CLK_OUT pins are tied together.

Connected in this way, is there any risk of back feeding:

Causing damage to the inactive device
Impacting the signal integrity of the outputted clock.

Is the output tied to ground when disabled?

Thanks for any help.

over 4 years ago

0 Noel Fung over 4 years ago

TI__Guru* 81400 points

Hi Sam,

The output is not Hi-Z when it is not used (CLK_REQx = 0), so it will hurt the output of another CDC device if their outputs are tied together.
Depending on the clock frequency, the simplest way is use two diodes to isolate the outputs.
Other solutions are, for example, use an analog switch to mux the outputs or pick up another input mux embedded clock buffer from our portfolio.

0 Sam460 over 4 years ago in reply to Noel Fung

Prodigy 20 points

Thanks Noel. We'll have a look for an alternative solution then.

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CDC3RL02: Back feeding and 2 devices in parallel