ESP8266 Community Forum

- Wed Sep 07, 2016 2:51 pm #54656 I am using 24 Shift Registers (TPIC6B595N) and I need to know if I should use something to help drive the RCK & SRCK buses. From searching and posting people tend to recommend using a buffer to do the job (I was going to use the SN74AC244NE4). I have been unable to work out properly which buffer, and how many, I need to use though as I have no idea how much current they need to handle. I plan to run the TPIC6B595N's at a high clock rate.

Any help would be much appreciated!

- Wed Sep 07, 2016 3:07 pm #54658 BTW, when you says "24bits", I presume you are daisy chaining 3 of those chips to get 3x8=24.
Why do you need 74AC244 to drive RCK and SRCK, they can be drive directly from GPIOs.

- Wed Sep 07, 2016 3:44 pm #54659 I mean 24 individual TPIC6B595N's. I had read that when you get that many chips you need more current then an individual GPIO can supply, especially when running them with a high frequency.

- Wed Sep 07, 2016 4:05 pm #54662 According to the specs, the Iil and Iih are 1uA, so it should not be needed since GPIO can drive 12mA.
Also, high speed definition is relative, GPIOs are not producing 100Mhz, it is limited by your software toggling them. So, conclusion : I don't think you need any clock driver.