SN74LS156: Looking for alternatives

Arttu Rasanen

Part Number: SN74LS156
Other Parts Discussed in Thread: SN74AHC238, TPL7407LA, TMUX4052

Tool/software:

Hi all

I'm looking for an alternative for the SN74LS156 decoder/demultiplexer IC which would have the following characteristics:

3-to-8 decoder with "select-low" outputs,
operating with supply voltages down to 3 V,
open-collector (or open-drain) outputs,
allowed off-state voltage of 15 V on outputs.

Does this kind of logic IC even exist? Could I use CD4028 + 8 discrete transistors to achieve these requirements? Although I am not sure if the CD4028 could operate with 3 V supply.

Thank you!

8 months ago

0 Clemens Ladisch 8 months ago

Guru 317260 points

Open-collector outputs, especially with 15 V tolerance, are unusual.

You'd have to combine an active-high decoder like the SN74AHC238 (or any other '238) with drivers like the TPL7407LA (with only 7 channels) or transistors.

0 Arttu Rasanen 8 months ago in reply to Clemens Ladisch

Prodigy 120 points

Thank you for your advice and recommendation regarding SN74AHC238.

In addition, I just found out about the 74HC138 decoder IC. Can this IC drive the EN signals of TMUX4052 muxes if the muxes' supply voltage is 15 V and the decoder is running off MCU supply (3.3 V)? Will these different supply voltages cause problems?

+1 Clemens Ladisch 8 months ago in reply to Arttu Rasanen

Guru 317260 points

The TMUX4052 does support low-voltage control signals. But is has a high on-resistance and does not allow loads of more than 10 mA.

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SN74LS156: Looking for alternatives