• Resolved

TLV3691: TLV3691 output current

Part Number: TLV3691

The datasheet output voltage vs. current in the TOC in the datasheet is a little confusing. It looks like the current range presented is 0-0.3mA at 0.9V bias. But the part is rated to 35 mA sourcing (at 6.5V bias). The spec says to refer to the ToC, but the data for 6.5V isn't there. I don't understand how the output voltage scales at different bias points, like a typical 3V bias. Do you have that data?

Thanks,
Dan

  • Hello Dan,

    The 35mA is the short circuit current at 6.5V supply. This is the minimum amount of current expected if the output were shorted to the opposite rail.

    Output drive drops considerably below 1.2V supply, as can be seen by the steep change in the supply current graphs <1.2V. This is a nanopower (75nA) device, so it is not expected to drive heavy loads - usually just a GPIO wake-up pin.

    The Graphs being referred to are Figs 3 thru 6. The graphs have both 0.9V and 6.5V curves.

    Digging through some char data, I found the "missing" 2.7V short circuit graph, which fills in  between 0.9 and 6.5V.

    So it looks to be about 7mA sinking and 11mA sourcing at 25C.

    Regards,

    Paul Grohe

    TI Comparators (CMPS) Applications Group

  • In reply to Paul Grohe:

    Great answer. The graph is useful. I think for applications that really want to be low power, we have to disconnect everything leaky (caps, mcu, etc.) from the supply voltage. Otherwise, the nanoamp level comparator performance doesn't buy much. For a new product, it would be great if the output behaved like a FET and could power a low current MCU, like NRF52 at 1.8 or 3.3V. WIthout the FET to disconnect the downstream circuits from the supply voltage, the comparator is like half a solution for nanoamp level applications. For my device, I'll insert the Nexperia PMZ950UPEYL to switch on the MCU supply. 

  • In reply to Dan Allen15:

    Hi Dan,

    Yes. At sub-microamp system supply levels, everything gets scrutiny and requires a different design mindset. You will see that almost all the nano amp comparators have push-pull outputs, as this eliminates the need for power-wasting pull-up resistors. Diodes can be used to "OR" outputs if needed.

    You can easily drive the gate of a logic level P-Channel MOSFET directly with the comparator output to turn on the power for the rest of the circuit. MOSFET gates do not need any current and the TLV3691 push-pull output would ensure that the gate is fully on or fully off (and not waste any current!).

    Regards,

    Paul Grohe

    TI Comparators (CMPS) Applications Group

  • In reply to Paul Grohe:

    Right. Push-pull is super useful. I just meant that it would be useful if it had a current vs. voltage response that was more like an ideal switch.