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SN74LS2323: Biasing question for reference pin

Raphael Robertazzi
Prodigy 10 points
Part Number: SN74LS2323
Other Parts Discussed in Thread: TLV713

Provide case details or comments: My concern is that when I use a number of these parts (lets say 5 on one design), I typically bias the reference pin with one common connection to a voltage divider. This would be for A 5V power supply operation, I would usually use a voltage divider, 5V to 1k ohm to 665 ohms to GND, then pick off the voltage at the 665 ohm resistor which is ~2V for the reference. The common strobe is always tied to GND (so part is enabled)

My question is, how much current does the reference input (pin #6) need, is the network I described sufficiently low impedance to bias all five in parallel?  What would be a safe bias network to bias 5 parts from a common reference, is a voltage reference needed or is a resistive voltage divider sufficient?

  • 0
    Guru 316760 points

    As shown in the schematic on page 2, the line and reference inputs behave the same.

    The electrical characteristics table on page 4 shows the maximum input currents. The −100 µA value appears to be a leakage current at the most extreme temperature; the 500 µA current goes through the 1.8 kΩ resistor and two transistors, so it will scale down with voltages lower than 3.4 V.

    1 mA through 1 kΩ is 1 V; you probably cannot afford such an error. Use something like the TLV713‍20.