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AM26C32: How to ensure VOH is over 4V

Shinichi Inoue
Guru 21721 points
Part Number: AM26C32

Dear Specialists,

My customer is considering AM26C32 and has questions regarding VOH.

I would be grateful if you could advise.

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According to AM26C32's datasheet, VOHmin is 3.8V.
Since VIHmin of the receiving side CPU is 4V, I want to make sure that the VOH of AM26C32 is 4V or higher.

Could you please answer listed below.

① Is the VoH of AM26C32IPWG4 correct at 3.8V?

② What kind of external circuit should I configure when receiving the output signal (3.8V) with a Vih min 4V CPU?

･If a pull-up resistor is connected to the output terminal Y, will there be a problem with voltage wraparound?
I think there is no problem since the output terminal has a zener diode, is this correct?

③What is the voltage that can be applied to output terminal Y? Is the configuration connected to 5V via a pull-up resistor within the rated range of the output terminal?

The voltage that can be applied to the output is –0.5 to VCC + 0.5.
When the power of AM26C32 is OFF, it needs to be 0.5V or less. Is that correct?

④What is the the other 4ch receiver of recommended with min 4V output?

I could not find any other product VOHmin>4V.

⑤Datasheet P.6 Figure 5-1. Output Voltage vs Input Current shows the relationship between output voltage and logic input current.

It seems possible to increase the output voltage to 4V or more by reducing the logic input current to 5mA or less.

If so, could you please let me know know how to limit the logic input current.

⑦Could you please let me know If there is any other way to ensure VOH is 4V or higher, .

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I appreciate your great help in advance.

Best regards,

Shinichi

  • +1
    Guru 317370 points

    Figure 5-1 is labelled wrong; the X axis should be output current.

    VOH is specified for an output current of 6 mA, i.e., the worst-case output resistance is 200 Ω. That current will happen only with a strong pull-down resistor; when you have a pull-up resistor or no resistor, the actual output current will be a few µA, and the actual output voltage will be above 4.9 V.

    When the AM26C32's power is off, you must not apply a voltage to the outputs. In general, the easiest solution is to connect the pull-up resistor to the same power supply.

  • 0 in reply to Clemens Ladisch
    Guru 21721 points

    HI Clemens,

    Thank you for your reply.

    I understand. When strong pull down is connected, the output is 3.8V. 

    I'll share this information with the customer.

    I appreciate your great help and cooperation 

    Best regards,

    Shinichi