• State
  • Replies 7 replies
  • Subscribers 63 subscribers
  • Views 127 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

BQ75614-Q1: BQ75614-Q1 UART TX-Pin State in shutdown mode

Gyuner Idrizov
Prodigy 20 points
Part Number: BQ75614-Q1

Tool/software:

Hello TI Team,

regarding to datasheet the TX-Pin should be high impedance in shutdown mode but i am measuring 3,2V at the output.

MCU and BQ75614 have direct connection with each oder and when we turn off the 5V supply (DCDC Converter) of MCU, BQ chip going to shutdown mode because of  long communication timeaout (2s).

In this case it starts to flow some current (6mA) from BQ Uart TX-Pin to the MCU over 47R resistance. It seems that current flowing over internal gpio diode of MCU to the 5V-Power.

But TX-Pin shouldnt have any voltage at shutdown mode. Propably because of 6mA  current over the TX-Pin and CVDD, is also CVDD volatge is very low (3,51V). 

thank you for your help!

sincerely

  • 0
    TI__Intellectual 860 points

    Hello,

    The default action for the BQ75614 during comm timeout is to go into sleep mode. Not shutdown, unless it's configured in the register map. During sleep mode, GPIOs that have been turned on, will remain turned on. This could be the reason that you continue to see GPIO pins active.

    Best,

    Zachary

  • 0 in reply to Zachary Balov
    Prodigy 20 points

    Hi,

    we set the "CTL_ACT"=1 and after timeout device is in shutdown mode. I can see it from AVDD and DVDD (they are turned off).

    i am measuring the voltage at UART-TX Pin not on GPIOs.

  • 0 in reply to Gyuner Idrizov
    TI__Intellectual 860 points

    Hello,

    Is this on an EVM or your board design? Depending on the layout, RX and TX pins can be pulled up to AVDD, which could remain on during shutdown mode.

    Best,

    Zachary 

  • 0 in reply to Zachary Balov
    Prodigy 20 points

    Hi,

    AVDD is turned off in shutdown mode. My pull-up resistors are connected to 5V supply of MCU and 5V suppy is also turned off in shutdown mode. For testing i have removed pull-up resistor on TX pin and i can see TX is not high impedance. On the other hand it is not possible to get 6mA current over the 10K pull-up resistor.

    Datasheet says: TX is high impedance in shutdown mode but on my pcb it is high. Is there any possiblitiy to turn off uart interface?

  • 0 in reply to Gyuner Idrizov
    TI__Intellectual 860 points

    Hello,

    Can you send me a schematic for your PCB for me to take a look at?

    Best,

    Zachary

  • 0 in reply to Zachary Balov
    Prodigy 20 points

    Hi, 

    unfortunately i am not allowed to share the schematic.

    Maybe i should ask the question differently:

    from following text i am understanding that the TX Pin in Shutdown State is high impedance. Is it correct?

    "The TX pin must be pulled high through a resistor on the host side of device to prevent triggering an invalid
    communications frame when the communication cable is not attached, or during power-off or SHUTDOWN state
    when TX is high impedance. TX is always pulled to CVDD internally while in ACTIVE or SLEEP mode."

  • 0 in reply to Gyuner Idrizov
    TI__Intellectual 860 points

    Hi,

    Testing on our EVMs, TX being high in sleep mode is normal behavior for our device.

    Does the MCU you are using have a 3.3V logic or 5V logic?

    Best,

    Zachary