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SN74LVC07A: Looking for p2p compatible with MC74VHCT50ADR2G

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Part Number: SN74LVC07A

Customer is looking for p2p compatible device with On-SEMI MC74VHC50ADR2G. 

We found the SN74LVC07ADR could compete with as comparison table here. It looks the variation of the VIH and VIL is not good on SN74LVC07. i'm not sure if it is ok in application? or Is there more suited one you can suggest? Very thanks .

  • The '07 has open-drain outputs, and its inputs are not TTL compatible.

    None of TI's hex CMOS buffers with TTL-compatible inputs have the same pinout. You would have to go back to bipolar devices like the SN74ALS1034, but those do not have CMOS-compatible outputs.

  • In reply to Clemens Ladisch:

    Thanks. I have a little confused about it. I found there are CMOS(5V), LVTTL(1.8V, 2.5V and 3.3V) compatible as INPUT logic in the datasheet of "SN74LVC07ADR".

    1. Here are the comparison table i did for 3 sockets. Please double check if it is correct or not?

    2. The output type of the SN74LVC07ADR is OPEN DRAIN type, is this compatible with CMOS or TTL or none of both? 

    3. Do you prefer to recommend the SN54ALS1034A than SN74LVC07ADR? If so, what condition in application we need to check with to be compatible with MC74LVHCT50ADR2G?

    Regards

    Brian W

  • In reply to Brian Wang0928:

    1. This looks OK. Please note that LVTTL is for different supply voltages, and this does not matter for this comparison. And the ALS power consumption is higher than that of CMOS deices.

    2. In theory, open-drain can be compatible with anything. But in practice, it requires a pull-up resistor to generate the high voltage level, and the rising edge is very slow. So the LVC07 can be a P2P replacement only if the circuit already happens to have a pull-up resistor on that line, and if no high speed is required.

    3. The LVC07 requires CMOS voltage levels (VIH > 3.5 V). If a TTL-compatible input were not required, then the original circuit would probably have used the MC74VHC50DR2G instead. Therefore, it is likely that the LVC07 will not work.

    If that circuit can handle TTL levels at the buffer's output, then the ALS1034A output will work with it. But if the MC74VHCT50ADR2G was used to convert TTL signals into CMOS signals, then the ALS1034A will not work.

  • In reply to Clemens Ladisch:

    Thanks.

    On the customer's schematic, there are three pull-up resistors of 10K-OHM with +5V at output of the LVC07A.  and its bias power is +5V. It looks the output can handle the output logic of the TTL or CMOS. 

    The purpose of this application is for the level shift usage that from 3.3V to 5V, and then to control the downstream circuit as the 7-segment LED and hardware switch. The signal speed is not fast. 

    You mentioned previously that the VIH needs to be higher 3.5V for CMOS LEVEL, so the LVC07A could not be used based on below circuitry, correct? I'd like to confirm with you this. Thanks. 

  • In reply to Brian Wang0928:

    The pull-up resistors at the outputs would indeed allow open-drain outputs. But the input voltage prohibits using LVC inputs.

    The resistors at the outputs also pull the high-level TTL output voltage up to 5 V, so it is possible to put the SN74ALS1034 into this circuit. The only downside might be its power consumption.

  • In reply to Clemens Ladisch:

    So the LVC07 can not be used due to input logic!

    It looks the SN74ALS1034 has no SOIC with higher temp of -40 to 85degree/105degree? Correct?

    Customer need p2p compatible for 2nd source solution. please advice. thanks. 

    Regards

    Brian W

  • In reply to Brian Wang0928:

    The SN54ALS1034 has a wider temperature range.

    If the customer cares about second sources, it would be a better idea to design with a more common device such as the MC74VHCT125A/‌SN74AHCT125.

  • In reply to Clemens Ladisch:

    Thanks.

    As you mentioned "The pull-up resistors at the outputs would indeed allow open-drain outputs. But the input voltage prohibits using LVC inputs" What's the meaning of the LVC inputs? From customer schematic, the input voltage is from 3.3V rail(voltage variation is from 3.1 to 3.4V). It would violate the VIH spec in "LVC07A", correct? in the LVC07A the VIH range is from 1.0725 to 3.85V. 

    Unfortunately, customer can not allow to change the package and pinout on the PCB  since exact p2p compatible with ON-SEMI device is needed on existing MP projects. If this is a case, it looks that there is NO right device to do 2nd source. double confirm with you.  

    Regards

    Brian W

  • In reply to Brian Wang0928:

    Yes; I used "LVC inputs" to refer to the input switching thresholds. (It does not make sense to look at the VIH range for other supply voltages; at VCC = 5 V ± 10 %, VIH is too high for a 3.3 V input signal.)

    There is indeed no P2P device.