SN74AHC574: OUTPUT waveform unstable and there is not CLKOUT

These signals violate the setup and hold times specified in section 7.6 of the datasheet.

What is the purpose of using a flip-flop in this circuit? Why are you mentioning the '245 transceiver? It's possible that that device, or a transparent latch like the SN74AHC573 might work better.

Hi Ladisch,

We want to check tsu and th with you.

For tsu, does it mean that we need input the data at least 4ns before clk posedge?

For th,the data status need to hold at least 2ns and the time duration need to smaller than clk high time? 

Roy

Hi Ladisch,

Below is our purpose. We use the chip to be the level shifter. After the chip, we want to transfer signal from 3V-5.5V to 3.3V. We used CLKOUTIN as DCLK and DEIN as example. 

Did you mean the SN74AHC573 may be a better solution for us?

Roy

Hi Lasdisch,

We need all of our signals output waveform should be synchronized. (Meanwhile, signal level should shift to 0-3.3V. So we used three D flip-flop and same CLK to trigger them.

Regards,

Roy

According to the waveforms shows above, the input signals already are synchronized.

Is this not the case? How exactly do you want the device to change the signal edges (the word "synchronized" is too vague)?

Hi Ladisch,

For schematic, I showed in the top. All of SN74AHC574 share the same CLK(TICLK) because we need all of our outputs changed at the same time. That's our purpose. And for input signal, the high level range will be 3V~5.5V. We also need to use D-flip flop to shift all of high level to  3.3V.

May SN74AHC573 be a better solution for us?

Regards,

Roy

What about the input signals? Do they change at the same time? What protocol is this? What device generates these signals?

Hi Ladisch,

Please see below. Honestly, I'm not sure why we can't get the expected output signal. Can you let me know if there is any appropriate solution(SN74AHC573?) that fit our request. If SN74AHC574 can fit our request, can you kindly let me know the reason that we can't get expected results? How to solve it? Many thanks.

RRegards,

RRoy

Hi Ladisch,

I am the EE R&D from AU Optronic .

As Roy's reply, our application requirement is only to change the amplitude of the input signal，without changing the relative relationship between them.

I guess your SN74AHC573 may achieve this function does it ?

So please give me some advice of device choosen.

Many Thanks!

When LE=H , output Q wlways follow input D

INPUTS          OUTPUT

/OE  LE  D         Q

L    H   H         H

L    H   L         L

L    L   X         Q0

H    X   X         Z

Thank you for your quick response.

I will evaluate this device what you suggested.

Thank you!

The 573 can indeed be used as a buffer. But it would be simpler to use a buffer as a buffer.

Thank you ! We will try SN74AHC541 in the first place.