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XTR111: Recommended operating voltage

May
Genius 9880 points
Part Number: XTR111

Hi Team,

Customer is looking for the typical value that can be used in the EF pin. Below is the details.

"We need to apply the EF pin of XTR111 to the controller. In the datasheet, the absolute maximum rating shows (Vvsp) + 0.5. The Vvsp is applied 18V in our case. This much voltages cannot be supported by the controller. Kindly provide us the typical maximum value that we can get at the EF pin."

Regards,
Maynard

  • 0
    TI__Intellectual 1955 points

    Hi Maynard,

    I'm not certain I understand your question. As the datasheet states, the absolute maximum voltage rating of the part's EF pin (with respect to GND) is from -500mV to VVSP + 500mV. It's best to keep the voltage on that pin between 0V and VVSP. The EF pin is an open-drain output with a weak internal pullup to 5V, but a strong external pullup to logic high should be used to ensure proper and reliable operation. The pin can be pulled up as high as VVSP without any issues.

    Now, if I understand what the customer is asking, they are concerned that pulling up the EF pin to VVSP will be too high a voltage for their controller or microcontroller's digital logic pins to withstand and are looking for a recommendation. Since it's an active low, open drain pin, they should be able to pull it up to their own 3.3V or 5V rail (assuming it shares a ground connection with VVSP) if they already have one. 

    The XTR111EVM makes use of a low-Iq TPS7A16 LDO to generate a 5V supply from VVSP in order to power the error flag circuitry, which could be another option. They could also just set the VREG of the XTR111 itself to the logic high voltage they want to use, but they need to be careful the pullup is sized so as to respect the 5mA current limitation of that reference (and be careful not to inadvertently sink any current greater than 50uA as well). 

    Cheers,

    Jon

  • 0 in reply to JMac
    TI__Genius 9880 points

    Hi Jon,

    Thank you for the information. 

    In the above explanation, does same logic apply to the OD pin of XTR111?

    Thank you in advance.

    Regards,
    Maynard

  • 0 in reply to May
    TI__Intellectual 1955 points

    Hi Maynard,

    Yes, similar logic applies. The OD pin has the same absolute maximum voltage limitations as the EF pin. It operates as an input, with the logic that a low signal enables the part output and a high signal disables the part output. The "low" logic threshold is OD <= 0.6V (to enable the output). For a stable output disabled "high" logic signal they should pull the pin up to at least OD >= 1.8V.

    If they do not have a need to disable the part output, they can tie OD to GND. Otherwise, they should indeed be able to use a pullup to their 3.3V or 5V logic, and then use an open-drain microcontroller output to pull down the pin and enable the part.

    Cheers,

    Jon