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AM26C31: higher output current on Ioh than specified on the datasheet

Kamal Najmi
Expert 3295 points
Part Number: AM26C31

hi

there is a maximum output current recommended of |20 mA|. See below.6.3

And it is recommended to use RT = 120 between A and B terminal. See below.9.2.1

 

We have exactly this configuration. But we measure a higher value at the output current due to the high differential output voltage.

 

Please check TI-datasheet and let me know the outcome at our meeting next week.

regards,

Kamal

  • 0
    TI__Guru 62910 points
    Hello Kamal,

    I agree, the recommended output current range would likely be exceeded during standard operation of the device (i.e., using a standard 100-Ohm termination). It looks to me like the 20 mA current is only showing up in the recommended operating conditions table because that is the current that is defined in the test condition for the output high and low voltage specs. It doesn't mean that you cannot operate the part with higher currents, then, it just means that the output voltages may be slightly different (higher output current would result in lower VOH and higher VOL).

    Best regards,
    Max
  • 0 in reply to Max Robertson
    TI__Expert 3295 points

    Yes I agree with you. But the data sheet says 20 mA (max.!). If it was a typical value it would be fine for me.

    so how should I understand the datasheet, could we updated the datasheet or making a new note.

    regrads,

    kamal

  • 0 in reply to Kamal Najmi
    TI__Mastermind 20820 points
    Hi Kamal,

    Max is out today so I am going to jump in and help. These parts are new to me so I will do my best with this. I believe the minimum current the driver can source a 20mA. The VOD level (2V) in the datasheet is guaranteed to be at a minimum of 2V through a 100ohms load (20mA)(100ohms) = 2V. Typically though the VOD is 3.1V through a 100ohm load so this tells me that the driver is typically sourcing something >20mA (i.e. 31mA). So, I think you are just misinterpreting the spec IOH and IOL spec in the datasheet.
  • 0 in reply to Michael Peffers
    TI__Expert 3295 points
    then, can you explain the Ioh and Iol max values?
  • 0 in reply to Kamal Najmi
    TI__Mastermind 20820 points
    Hi Kamal,

    I did a little bit of digging around and a colleague of mine pointed me to an old forum post that explains the problem here. Apparently the IOH and IOL spec could have been specified better in the absolute max table. I am not sure why it is speced this way but here is the post for you to review: e2e.ti.com/.../591216

    Please let me know if you have any more questions?