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AND Gate with Maximum number of inputs

Prodigy 210 points

Replies: 6

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Hi,

Regarding AND gate chips I have below queries :

1. What is the maximum number of inputs supported by AND gate chips. My requirement is to connect 8 signals (3.3V level) to AND input and generate 1 OUTPUT.

For this requirement what is the best solution you can provide.

2. I just checked on high level and found SN54ALS21A part. Can we use 2 nos of this chip at 3.3V Power ? (use 1 chip to connect all 8 inputs and use another chip to connect 2 OUTPUts of 1st chip to generate  1 OUTPUT). Whether this is the best solution or do you have any better plan?

3. If the plan as mentioned in point 2 is the recommended solution, then whether I can use the chip SN54ALS21A at 3.3V ? If yes then what are the VIH,VIL values for 3.3V power?

Regards,

Vijetha

  • Hi Vijetha,

    That is the suggested method. To use multiple and gates to and all the signals together. Another possible device you can use SN74LVC08. You can use our parametric search to specify inputs.

    Thanks!

    -Karan

  • In reply to Karan Kotadia:

    Hi Karan,

    If the method i mentioned in point 2 is suggested method, please answer my 3rd question (If the plan as mentioned in point 2 is the recommended solution, then whether I can use the chip SN54ALS21A at 3.3V ? If yes then what are the VIH,VIL values for 3.3V power? Datasheet gives VIH levels for few fixed Supply values, for 3.3V supply VIH/VIL not mentioned, kindly suggest)

    Regards,

    Vijetha

  • In reply to Vijetha HN:

    The SN54ALS21A was designed back in the day when steam engines could generate only 5 V, so it is not guaranteed to work at lower supply voltages.

    To find AND gates that run at 3.3 V, use the search function.

  • In reply to Clemens Ladisch:

    Apologies for mentioning wrong part number. The 4 input (2 circuits) AND gate part I got from search function was SN74HC21PWR. I was checking its datasheet and it says it can function from 2 V to 6V.

    Q1 : Whether it can work at 3.3V supply?

    Q2 : If yes, can you provide its VIH,VIL levels at 3.3V (in datasheet we have values only at 2,4.5,6V)

    Regards,

    Vijetha

  • In reply to Vijetha HN:

    HC devices work at any voltage between 2 V and 6 V.

    To get values for 3.3 V, interpolate between those given for 2 V and 4.5 V. See [FAQ] What method is best used for estimating specification values between those given in the datasheet?

  • In reply to Clemens Ladisch:

    Hi,

    Thanks Clemens for the help. Besides the SN74HC21, you are going to need a second chip with an individual AND gate to AND those two signals together. I can recommend the SN74LVC1G08 which is our most popular part.

    Thanks!

    -Karan