SN74AHC595: SN74AHC595

Kiran A

Part Number: SN74AHC595
Other Parts Discussed in Thread: SN74AHCT595

Hi,

I was working on a Multiplexing configuration, We had selected a Mux from AD-ADG5412. We will have multiple Muxes on our board while i was looking for options i found SN74AHC595 to be used as port expander. We have SPI on our board, can we use SN74AHC595 to drive the select lines of ADG5412 which has (Vih of 2.0 Max) and (Vil of 0.8 max ), Please let me know if you see any concern with this configuration.

over 6 years ago

0 ShreyasRao over 6 years ago

TI__Guru 64460 points

Hi Kiran,

What is the supply voltage being used and the external loading on the ADG5412? With 3 Vcc, the Vih 2V should be fine. But with 5V Vcc, the Vih is not sufficient. You could consider using the SN74AHCT595 which has 2V Vih for 5Vcc.

0 Karan Kotadia over 6 years ago

TI__Genius 16825 points

Hi Kiran,

What supply voltage are you planning to operate the SN74AHC595 at? There is a recommended operating condition table provided in the datasheet that contains the VIH and VIL spec of our parts. https://www.ti.com/lit/ds/symlink/sn74ahc595.pdf

Thanks!

-Karan

0 Kiran A over 6 years ago in reply to ShreyasRao

Intellectual 610 points

HI Shreyas,

Sorry to have provided wrong data, i meant (Vih -> 2V Min) in above query.

0 Kiran A over 6 years ago in reply to Karan Kotadia

Intellectual 610 points

3.3V.

0 ShreyasRao over 6 years ago in reply to Kiran A

TI__Guru 64460 points

The datasheet of AHC has min Vih of 2.1V for 3V Vcc. Hence, it cannot be guaranteed that all the inputs will be recognized as a high by the AHC device.

The ADG device if connected to the AHC inputs, wouldn't load the ADG outputs more than 1uA,( input leakage of AHC input pins) which will result in Voh higher than 2V, so you would be fine.

Logic

Logic forum

SN74AHC595: SN74AHC595