SN74HC574: Timing diagram for 3.3V application

Westlund

Part Number: SN74HC574
Other Parts Discussed in Thread: SN74AHC574, SN74HCS174, SN74HCS574

On page 4 and 5 in the datasheet:

The timing for 2 and 4.5V are specified in the table. We are going to use it in a 3.3V application. How can we calculate or find a table of timing for 3.3V in 74HC parts?

/Johan

over 3 years ago

0 Clemens Ladisch over 3 years ago

Guru 280000 points

See [FAQ] What method is best used for estimating specification values between those given in the datasheet?

Consider using the SN74AHC574 instead, which specifies 3.3 V values, and is faster, uses less power, has overvoltage-tolerant inputs, a wider temperature range, and is cheaper.

0 Westlund over 3 years ago in reply to Clemens Ladisch

Prodigy 50 points

We have considered LVC and AHC, but both of them only clamp input for negative voltage. We need to have clamped for both over and under voltage on output and input.

0 Emrys Maier over 3 years ago in reply to Westlund

TI__Guru* 96842 points

Hello,

The HCS logic family is our most recent addition to logic and is designed with input and output clamp diodes.

The SN74HCS174(-Q1) (6-channel DFF with CLR\) is currently available -- if you don't need the OE\ pin from the '574, then this might be a viable option.

The SN74HCS574(-Q1) is going to be released within the next year, and will have very similar performance to the '174 mentioned above.

Since the HCS family was designed to be part of the HC logic family, it has similar specifications (2V, 4.5V, 6V), so you'd still have to use linear interpolation to estimate 3.3V delays, however the performance at low voltage is much better than the old HC devices.

For example, max delay for CLK to Q on the HC574 at 2V is 225ns. The HCS174 under the same conditions has a max of 35ns.

Because of the Thanksgiving holiday in the U.S., TI E2E™ design support forum responses may be delayed from November 25 through December 2. Thank you for your patience.

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SN74HC574: Timing diagram for 3.3V application