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BQ40Z80: About PDSG preamp function setting of BQ40Z80

zhang jianhang
Prodigy 130 points
Part Number: BQ40Z80

Hi TI experts，

            

When I use Pin20 as PDSG, I found that after it is turned on, it is a high-level drive output, and the low level is active. Can I use the Pin20 to directly connect the G pole of the PFET for control? As shown in Figure 1.

In addition, after I turned on Pin20 as PDSG, I found that the power consumption of the protection board increased by 4 times (350uA increased to 1.5mA, as shown in Figure 2, Figure 3). After my analysis, I found that the increase in power consumption was caused by BQ40Z80 turning on Pin20 as PDSG function. Yes, is this normal?
1. If it is normal, the power consumption is too high. Is there any other way to reduce the power consumption?
2. Is it the reason for Pin20 to do high voltage drive output? Then if I change Pin16 as PDSG, will the power consumption be normal?

  • 0
    TI__Guru** 102455 points

    Hello Zhang,

    The PDSG pin is a P-channel drive, that's why it is active low. Are you using the EVM or custom PCB?

    Where are you measuring the current for gauge consumption? Current consumption will change depending on the FET drives active and the operating state, FET drives are not efficient.

    Sincerely,

    Wyatt Keller

  • 0 in reply to Wyatt Keller
    Prodigy 130 points

    Hi Wyatt，

            Thank you for your answer.
            I am using a custom PCB. If you use Pin20, you need to change the circuit as shown in Figure 1, and the PDSG can work normally.
            I am measuring the current draw on the main circuit of the protection board B-. I disassembled the preamp circuit and just turn on the PDSG, the power consumption increases, is this normal?
            Although Pin20 can do the PDSG function, the power consumption is too high, which is 4 times higher than the original one, which is unacceptable to customers. Is there any other way to solve this problem?

  • 0 in reply to zhang jianhang
    TI__Guru** 102455 points

    Hello Zhang,

    The PDSG current used should mostly depend on your external circuitry, there will also be some differences with pin 20 and pin 16 since the use different drivers to control the GPIOs.

    Sincerely,

    Wyatt Keller

  • 0 in reply to Wyatt Keller
    Prodigy 130 points

    Hi Wyatt

           I did two verifications,
          1. After I turned off the PDSG of Pin20, the power consumption returned to the normal 370uA, and the power consumption increased after re-opening the PDSG function.
          2. I dismantled the peripheral circuit of Pin20, which is equivalent to no peripheral preamplifier circuit. At this time, I turned on the PDSG function of Pin20, and the power consumption increased from 370uA to 1.3mA.

          Attached are some of my data.
           

  • 0 in reply to zhang jianhang
    TI__Guru** 102455 points

    Hello Zhang,

    I'm not sure what the expected increase in current is from the PDSG function on each pin since we do not directly spec this. The GPIOs are not as efficient as the FET drives so they will draw more current. It appears the it is not related to your circuit since it is drawing the same current regardless of the connection to it. I will need to check if this is the bias current for the GPIO pins.

    Sincerely,

    Wyatt Keller

  • 0 in reply to Wyatt Keller
    Prodigy 130 points

    Hi Wyatt,

                 Looking forward to your reply, I'm stuck with this.
                 At the same time I will try other methods, such as setting some other registers to solve this problem.
                 thanks.

  • 0 in reply to zhang jianhang
    TI__Guru** 102455 points

    Hello Zhang,

    I will not be able to check this until next week. I will update here when I have tested the expected current.

    Sincerely,

    Wyatt Keller

  • 0 in reply to Wyatt Keller
    TI__Guru** 102455 points

    Hello Zhang,

    Pin 20 does draw approximately 1mA when active. You would need to use one of the other pins for PDSG if you are concerned about current draw. Technically PDSG should not be active for very long, I'm not sure why this would be a concern or have an impact on the overall current consumption of the application.

    Sincerely,

    Wyatt Keller

  • 0 in reply to Wyatt Keller
    Prodigy 130 points

    Hi Wyatt,

    This is not the case in my test. If Pin20 is selected as the PDSG, it is a PMOS drive output. It outputs a high level in normal state and a low level when it is active, which is in line with the PMOS drive circuit. When the PDSG is not working, it will always consume a current of 1mA. I guess when Pin20 is used as PDSG, it needs to consume energy to output high level, but this PDSG will bring a high power consumption problem and cannot use Pin20 as PDSG.

    Or is it possible to control the PDSG switch by issuing commands from the MCU?


    At the same time, I tested Pin16 as a PDSG. It is an NMOS driver. It outputs a low level in normal state and a high level when it is active, so that there is no problem of high power consumption when the PDSG is not active.

  • +1 in reply to zhang jianhang
    TI__Guru** 102455 points

    Hello Zhang,

    Yes the pin itself draws around 1mA when active, it does not matter what is attached to the pin that would cause additional current consumption. I see the issue, I would recommend using one of the other pins for PDSG if possible that will consume less power at idle.

    The PDSG has a test mode feature than can be controlled by command, but this would not be available when the gauge is sealed.

    Sincerely,

    Wyatt Keller

  • 0 in reply to Wyatt Keller
    Prodigy 130 points

    Hi Wyatt,

    Ok, I can only use other pins for PDSG function, thanks for your answer.