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AM26C32: About input resistance

Jimmy WANG
Genius 3605 points
Part Number: AM26C32

Tool/software:

Hi team,

Due to customers uses internal resistance of AMC26C32 to design like below.

They found some problems here. If get the product from Malaysia side. 

They believe that the internal input impedance is biased, which causes the OP voltage output to be low. They use other origins and don't have this problem>

Do you have any suggestion for customer reference?

  • 0
    Guru 295570 points

    Nominal values are not guaranteed. The input current can be up to 2.5 mA (see the II specification in section 5.6).

  • 0
    TI__Guru 62610 points

    Hi Jimmy,

    As Clemens pointed out, we don't guarantee a resistance here outside of the spec named 'Line input current' where an input voltage of 10V on this pin will be 1.5mA or less and a -10V on this pin will result in a -2.5mA or less. 

    -Bobby

  • 0 in reply to BOBBY
    Genius 3605 points

    Hi team,

    Could you explain why the input resistance can not be guaranteed? Because Torrance is big? or other process impact? thanks 

  • 0 in reply to Jimmy WANG
    TI__Guru 62610 points

    We only test/validate the leakage from the pin when the pins are at 10V and -10V. Because we don't specifically spec the input resistance in the datasheet for this device, we don't test/validate this. (We don't have min/max numbers for the input resistance besides the leakage current spec).

    -Bobby

  • 0 in reply to BOBBY
    Genius 3605 points

    Hi Bobby,

    pls see below. 

  • 0 in reply to Jimmy WANG
    TI__Guru 62610 points

    Hi Jimmy,

    Thanks for pointing this out (my mistake). I looked through the validation data for the newer parts (with the new die). The average/typical is closer to 20k ohms at room temperature when Vcc=5V. We don't have the data for the older parts (old die design) to compare to though.

    -Bobby

  • 0 in reply to BOBBY
    Genius 3605 points

    Hi Bobby,

    Do you mean that all the products produced from now on will be 20KR?
    Instead of 17KR? My customers  use ICs made in Malaysia without any problems.
    Coming from Mexico will make abnormal

  • 0 in reply to Jimmy WANG
    TI__Guru 62610 points
    Jimmy WANG said:
    Do you mean that all the products produced from now on will be 20KR?

    It's not really a guarantee. The data collected is from one lot (one fab) and most of the data points collected showed the resistance is close to 20k. I don't know what the typical was for the older die. But typical values in datasheets aren't guaranteed values and this parameter doesn't have a max limit. We only guarantee the minimum should not be lower than 12k.

    -Bobby

  • 0 in reply to BOBBY
    Genius 3605 points

    Hi Roman,

    You mention the validation data for the newer parts (with the new die). The average/typical is closer to 20k ohms at room temperature when Vcc=5V.

    Can I interpret this as the typical value produced by the old mold is 17KR?

  • 0 in reply to Jimmy WANG
    TI__Guru 62610 points

    Hi Jimmy,

    Jimmy WANG said:
    Can I interpret this as the typical value produced by the old mold is 17KR?

    I don't know. Typical values are what design aims for and from silicon perspective if the validation value is larger than the min and lower than the max, we don't always change the typical value. Without testing the old dies, we don't know for sure if the old die had validation data that lines with up 17k ohms as their room temp typical. This spec looks like it covers Vcc between 4.5V and 5.5V with temps from -55C to 125C so this typical value probably moves with temp and voltage. 17k is probably the average across temp and voltage. At 5V and 25C the old die could have a different resistance. 

    -Bobby