SN74AVCH1T45: Clarification on SN74AVC1T45 / SN74AVCH1T45 spec

Dilip Namdeo Mohol

Part Number: SN74AVCH1T45
Other Parts Discussed in Thread: SN74AVC1T45, SN74AUC1G17, 2N7001T, SN74AUP1G17, SN74AUP1T34, TXU0101, SN74LVC1G17

I am planning to use SN74AVC1T45 and SN74AVCH1T45 to level shift 25MHz clocks. An example circuit in our application is shown below.

I need clarification on “rise / fall rate” spec. Datasheet shows max dt/dv as 5ns/V. If we consider a clock on 1.8V domain, this translates to a max of 9ns. Does it mean we cannot use this IC to level translate a slower clock like 8kHz which is expected to have a rise time of roughly 12.5us?

The 25MHz clock above has a rise/fall time of 6ns. SN74AVC1T45 / SN74AVCH1T45 should not have any problem dealing with such rise times, right?

over 1 year ago

0 Clemens Ladisch over 1 year ago

Guru 279220 points

The rise/fall rate is not directly related to the frequency; it describes the slope of the signal edges, not the interval between the edges. If your signal has slower edges, you need to use a different device, probably with Schmitt-trigger inputs.

For unidirectional applications, consider unidirectional level shifters like the 2N7001T, SN74AUP1T34, or TXU0101. For shifting to a lower voltage, you can also use any buffer with an overvoltage-tolerant input, i.e., SN74AUC1G17/SN74AUP1G17/SN74LVC1G17.

0 Dilip Namdeo Mohol over 1 year ago in reply to Clemens Ladisch

TI__Intellectual 1560 points

Thanks for quick reply

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SN74AVCH1T45: Clarification on SN74AVC1T45 / SN74AVCH1T45 spec