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BQ2205LY: BQ2205LY

PIerluigi Rossetti
Intellectual 350 points
Part Number: BQ2205LY

Hi Team,

I have an easy question about the function RST pin 16 BQ2205, this function is Input or Output?

In the datasheet  on  Page 1 in the scheme is Input  for push botton,  and in pag 2 is declared  as RST low-level input voltage, VIL.

In the some datasheet on Page 3 and 5 is declared  as Output.

thank a  lot

Pierluigibq2205ly.pdf

  • 0
    TI__Genius 12630 points

    Pierluigi,

    /RST is active-low open-drain OUTPUT.

    -Michael

  • 0 in reply to Michael_DeSando
    Intellectual 350 points
    Hi Michel,
    the Answer isn't clear,
    I asked you to investigate on the signal RTS, because on scheme is drew as INPUT with a pull-up, for push to gnd by button .. will be a reset to BQ2205 ...

    Then, you didn't read at pag 3, where describe the RECOMMENDED OPERATING CONDITIONS, is wrote electrical state conditions... the signal RST: Low-level input voltage, VIL −0.3 0.8 V and High-level input voltage, VIH 2.2 VCC + 0.3V.

    My customer in fact if put a pull-up 100K or 10K, and function .. but without pull-up there are anomaly when write the RAMs the CS1 and CS2 bad run.

    Now, you tell me that signal is OUTPUT ...

    Please could verify in BU specified the real state this RST.

    Best regards
    Pierluigi
  • 0 in reply to PIerluigi Rossetti
    TI__Expert 4045 points
    Hi Mike,
    can we get an answer urgently today? we need to understand if the problem detected by the customer could be solved simply adding a pull-up resistor; but if the pin is only output, then pull-up is not needed if the output is not used and the problem could be caused by something else.
    Thanks
    Umberto
  • 0 in reply to Umberto Frangi
    TI__Genius 12630 points
    This device does not belong to my group but I believe I can answer still. I opened the datasheet and on page 5 it makes it very clear /RST is an output. /RST is active-low open-drain OUTPUT. A pull-up resistor is required.

    -Michael
  • 0 in reply to Michael_DeSando
    TI__Expert 4045 points

    Hi Mike,

     can you move these threads into the correct place, to get a proper answer?

    I am not convinced about what you said and I think this /RST pin could be an I/O.

    In fact can you specify at pag.3  VIL/VIH for an output?

    And could you connect a pushbutton to an output as in the front page?

    It is normal to place a pullup resistor on an open drain output if you use it, but in the customer application /RST is not used.

    And there is a difference in the behavior with and without this resistor; this means /RST could be an input and placing the pullup you force the input high avoiding noise issues that could reset the device.

    Thanks

    Umberto

  • 0 in reply to Umberto Frangi
    TI__Guru 54715 points
    The /RST pin is an output with an input function, thus it has recommended voltage levels as an input. As an output it has the characteristics described. It is an open drain and must have a pull up resistor. The pushbutton is optional, but the pull up resistor is not optional for normal operation as /RST affects other functions in the part. The output voltage spec is 0.4V max with 1mA load (page 3 of the data sheet), this condition would allow a 3.3 k ohm pull up resistor. Since /RST is an open drain output it can be pulled down by an external source such as a switch. On page 7 it indicates the pull up resistor for the pin should not exceed 10 k ohms if a switch is used. A pull up must be used on /RST even if the pin is not intended to have other use.
    We don't know why the author did not list the pin as an IO.