AnsweredAssumed Answered

Cascading 74LVC595A shift registers

Question asked by Franz Forstmayr on Aug 1, 2016
Latest reply on Aug 3, 2016 by Bulat Karymov

Hey,
the 74LVC595A shift registers reads the incoming data with the rising clock edge. The serial data output is also clocked on the rising edge of the SHCP. Could there be a problem when cascading several 74LVC595A devices, due to propagation delay and  hold time? I mean the cascaded register has a hold time of minimum 1.5ns at 3.3V, the data output could have a propagation delay of 1.5ns. This means the second register can see a changing input pin 1.5ns after the clock pulse, so layout effects of a few ps can make my device unfunctional by reading strange things.

Is there a good way to avoid problems like this? Why isn't a additional Q7S flip flop in the device, which latches the data out at the falling clock edge?

Yours Franz

Outcomes