LM211: Maximum current

Part Number: LM211
Other Parts Discussed in Thread: LM111-N, LM111

Hi Team,

Greetings. I need your confirmation for our customer's concern. 

What is the maximum allowed current for LM211 for a given fault. If one of the input pins was shorted to a supply voltage, what is the maximum current it can withstand?

Thank you. 

Best regards,

Jonathan

  • Hello Jonathan,

    See the graph in figure 5 of the LM211 datasheet.

    The output is capable of up to 120mA peak, but the current will be dominated by the thermals. As the die heats up the current will decrease up to the point of thermal runaway and destruction if Abs Max die temp is exceeded.

    It would behoove the user to limit the current if possible, usually with a series resistor, if the output goes off-board or through a wiring harness.

  • Hello Paul, Thank you for that information, but could you tell me about the input current limit to the input pins? I am going to limit the current into the device but for documentation purposes I need to know what the maximum current that can be applied to the device and is not damaged during an overvoltage fault condition. Typically the input current limit is 10mA for most devices however for this device the number is not given in the datasheet. 

  • Hello Manuel,

    Sorry..I missed the "input" in the first post - usually these type of questions are for the Output.

    These older devices do not have ESD clamping structures to the supplies. So the upper input range is limited by the breakdown of the devices, and the lower range is limited by the reversed body diode.

    I was not able to find any ratings for this, or the other family devices. The only rating would be 5mA max on the strobe pin (10mA for the LM111-N). The strobe pin should NOT be tied directly to any supply and should be limited to <5mA.

    I did find a mention of 100mA in the original LM111 Application Note AN-41  (Application Hints section, 5th paragraph)

    https://www.ti.com/lit/pdf/snoa642

    Though AN-41 was written by the original designer (Bob Widlar), I am personally uncomfortable with 100mA - that is just too much.

    These older processes are fairly robust. 10mA is generally a starting point for an Abs Max, but, since the upper range is not protected by any clamps, I would be more conservative to protect these unprotected junctions.

    As long as you stay within the Abs Max range, the currents should be well below a milliamp. But going below V-, or well above the Abs Max voltages, where avalanche or Zenering can occur - and that can lead to latching and high currents (and damage).

    So I would say 10mA max, but try to keep it as low as possible, especially on the positive side.