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Original question:

LMH1297: Internal pull-up / pull-down

LMH1297: internally pull-up / pull-down

K.Yaita
Guru 29720 points
Part Number: LMH1297

Hi Team,

Regarding LMH1297datasheet, IIH and IIL specification shows the following.
----------------------------------------------------
- IIH
LVCMOS (EQ/CD_SEL, SDI_OUT_SEL, ENABLE)  -> 15uA(max)
LVCMOS (OUT0_SEL) -> 65uA

-IIL
LVCMOS (EQ/CD_SEL, SDI_OUT_SEL, ENABLE)  -> -50uA(min)
LVCMOS (OUT0_SEL) -> -15uA(min)
----------------------------------------------------

I believe EQ/CD_SEL and OUT0_SEL are opposite in datasheet because EQ/CD_SEL is internally pull-down and others are internally pull-up.
Is my understanding correct?

Best Regards,
Yaita

  • 0
    TI__Guru* 93670 points

    Hi Yaita-San,

    I used ammeter that measures in order of uA in two cases below:

    1). OUT0_SEL: As you noted this pin has internal pull up. I had one end of the ammeter to EQ/CD_SEL and another end to GND and measured 28.5uA. With 2.5V supply, this means we have ~87K ohm internal pull up. In data sheet we say input high leakage of 65uA. It means minimum internal pull up resistor can be 2.5/65uA=38K-ohm.

    2). Next since we have internal pull down for EQ/CD_SEL i connected one side to VDD(~2.5V) and another to EQ/CD_SEL pin and measured 37.1uA. Given 2.5V supply, this means we have about 67.3K Ohm resistor. In data sheet we specify input low leakage of 50uA. This means at minimum we can have 2.5V/(50uA) or 50K ohm. 

    These parameters essentially indicate maximum leakage current or minimum internal resistance value. Given these, i don't see an issue with the data sheet parameters.

    Regards,, Nasser

  • 0 in reply to Nasser Mohammadi
    Guru 29720 points

    Hi Nasser-san,

    Regarding IIH of OUT0_SEL (internal pull up), the datasheet shows 65uA(max) under the test condition is Vinput=VIN.
    Do you refer it is correct?
    I believe 65uA(max) is the value of IIL not IIH.



    Best Regards,
    Yaita

  • 0 in reply to K.Yaita
    TI__Guru* 93670 points

    Hi Yaita-San,

    I did more measurements. I agree OUT0_SEL IIH and IIL should be swapped. So IIL should be 65uA instead.

    Regards,, Nasser