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BQ76952: bq76952下命令开启预放管时间问题

user5916746
Intellectual 550 points
Part Number: BQ76952


采用BQ7695202带CRC模式，通过命令开启预放管（此时主放电管是关闭状态），抓到的命令完成到bq76952执行预放打开的时间如下： 1通道为bq76952的I2C的SDA，2通道为预放开启的输出，3通道为按键，因示波器原因目前不能清晰的展开波形，目前多次测试，外围条件统一，测试到开启预放的命令下完到BQ7695202执行开预放的时间为500ms-1500ms左右，目前测试到这个时间范围比较大，执行主放电管开启和关闭同样也是下命令开启和关闭的时间就很准，不知道是什么原因造成的？

  • 0
    TI__Guru*** 130456 points

    您好，是否方便将电路发过来看一下。

  • 0 回复 user5916746
    TI__Guru*** 130456 points

    您好, 电路看起来没有问题.

    1. Do you have the FET_EN bit set low so you can use the PDSGTEST() command? If so, this generally not recommended if you want to use PDSG

    2. Is the device in SLEEP mode prior to sending the command? This is critical because in SLEEP mode, the device polls once a second to check if any commands were received whereas in NORMAL mode it polls every 250ms. If its in SLEEP, a delay of over a second isn't unheard of because it can take upwards of 250ms for the FETs to turn on in addition to the 1s polling.

    3. What is the button supposed to represent? Is this the trigger for the command to be sent?

    I would recommend looking over Table 6-9 Timing of Events in the Technical Reference Manual as well as Table 16-2 Startup Sequence and Timing in the datasheet for more info on the device timing.

  • 0 回复 Star Xu
    Intellectual 550 points

    FET-EN目前一直是设1的，按键是外围提供高低电平，控制MOS开或关，按键拉高是关主放管，拉低会先唤醒MCU，mcu通过通讯线发命令开预放管，此时BQ76952在通讯，是无法进入SLEEP模式的，测试的外围条件都是一致的，但是测试到开预放的时间0.5s-1.5S左右，但是测试通过按键拉高，MCU唤醒，通过通讯线下命令去关主放管的时间比较固定，基本0.5S左右，不会跑到1s以上

  • 0 回复 user5916746
    TI__Guru*** 130456 points

    您好，

    The device is still able to communicate while in SLEEP mode. It is just evaluated less often than in NORMAL mode. I wanted to double check that there wasn't an miscommunication that the device has to be in NORMAL mode to communicate. Could you use the SLEEP_DISABLE() and then re-try this to see if produces different results?

    Also for more clarification, is it taking roughly .5-1.5 seconds to go from the button press to the PDSG turning on or something else like from the I2C message being sent to PDSG turning on?