• State Resolved
  • Locked Locked
  • Replies 6 replies
  • Answers 3 answers
  • Subscribers 64 subscribers
  • Views 1173 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

BQ27220EVM-744: Measuring current consumption, and wake-up, slpwakechg and sleep questions

arnon b
Prodigy 100 points
Part Number: BQ27220EVM-744
Other Parts Discussed in Thread: BQEVSW, BQ27220

hi,

I'm working with the bq27220EVM in order to use the device as a Columb Counter.

We want to reduce the consumption current, and to be in 'sleep mode' most of the time, and I have few related questions:

  1. How can I measure the consumption current with the EVM?
    I realized I need to connect to the BAT PIN (am I right?) but i can't find a way to do this in the EVM.

  2. Does entering and exiting 'sleep mode' depend on the current or on the average current?
    In the 'refrence manual' (SLUUBD4) there are conflicting places (p 50-51Figure 4-1and section 4.5.2).
    I coulden't found a consistent answer in my tests.

  3. I'm not sure how to work with the 'wake up comparator'.
    I coulden't find information about this in the Data Sheet (SLUSCB7) as well as in the 'refrence manual'.

    What are the 'comparator threshold', how can I change and select them?
    Does the [WAKE_EN] always need to be o to enable sleep mode? (as written in the Data Sheet section 6.5 remark 2)
    Does IWAKE ('refrence manual', section 4.5.2) is depand on these registers? If not, what it is?
    .

  4. slpwakechg - "Accumulate estimated charge on wake from sleep when Current() > Sleep Current but not enough to trigger wake event. Enabled when set." ('refrence manual', section 4.1.2)

    I notice that the 'row columb count' is accumulating In sleep mode even when [slpwakechg] is 0, so I don't understand what does it do.
    What does it mean "when Current() > Sleep Current but not enough to trigger wake event" 

  5. And my last quastion, I want to be sure that the 'electrical load' is accumulated to the 'row columb count' register.

thank you very much

Arnon 

  • 0
    TI__Guru* 76230 points
    1. Bat pin is connected to pac+ on the EVm so connect an ammeter between the battery and the pack+ pin
    2. Current
    3 When the gauge is in sleep mode, it wakes once every 20s to take measurements. The wake comparator ensures the gaugecan wake up within that 19s when it will be in sleep mode. The TRM for this device skipped how to set the iwake currents, but see section 4.3.7 for the sister device on how to set that value.www.ti.com/.../sluube6.pdf

    4. I believe that is not properly defined. That flag just allows for the gauge to estimate current that may have been missed while the gauge was in sleep given it wakes once every 20s. if the gauge wakes and the current measured is above the sleep, it assumes that current must have been flowing while in sleep and accounts for that in the passed charge..
    5.yes that is correct.
    thanks
    Onyx
  • 0 in reply to Onyx Ahiakwo
    Prodigy 100 points

    hi Onyx, thank you for your quick answer,

    I want to meaure the current to the gauge itslef, without the load current. There is a way to do it with the EVB?

    As I understand the slpwakechg accumulate estimated charge only when the current is larger then the sleep current. So if I want the gauge to accumulate a small estimated current while sleeping I can't use this option. Am I right?
    I thought of using the 'electronic load' to accumulating this small current.The disadvantage is that I need to estimate this current before the use, and can't cange it while working. Is there is another option to do this?

    I have one another question, what are the implications of the modes of operation (loading, unloading and relaxation)?
    Does this affect how the device works? Is the gauge current consumption get lower in 'relaxation mode'?

    thank you very much,

    arnon

  • 0 in reply to arnon b
    TI__Guru* 76230 points
    you can't measure the current to the gauge using the bqEVSW. You can have a small resistor between the battery and the Bat pin and measure the voltage drop or place an ammeter in between the battery and the bat pin.
    -slpwakchg is used to account for passed charge which the gauge would have missed due to being in a sleep state. So if you will have current flow while in sleep, then set that flag.

    The different modes are what the gauge uses to determine if it is in charge discharge or relax mode. pls see the technical refernece manual for further details. Those modes are very critical to the operation of the gauge but they don't affect the current consumption of the gauge
    thanks
    Onyx
  • 0 in reply to Onyx Ahiakwo
    Prodigy 100 points

    hi Onyx,

    I'm using BQ27220,

    Do you have information about exiting sleep mode in cases of short peaks in the load current?

    From which amplitudes and puls widths the gauge is expacted to wake of?

    I thout about using a capacitor in parallel to Rsense to overcome this peaks, do you have recommended desgin for this?

    Other option, I dont no if possible, is to determine the wake-up threshold to be the 'average current' register, insted of the 'current' register, and by that smoth this peaks' influance. is it possible?

    thank you very much

    arnon

  • 0 in reply to arnon b
    TI__Mastermind 24870 points
    Please refer to the TRM.
  • 0 in reply to Kang Kang
    Prodigy 100 points

    hello

    My application is IOT style, and has long periods of low current and short pulses of high current.

    I'm checking the bq27220 to be a coulomb counter for my applecation.

    • What is the bq27220 ability to detect short pulses? 

    In addition, we want to put a capacitor in parelel to Rsense to average the current, in cases of higher than permissible pulses.

    • Can we add this capacitor in parelel to Rsense without damaging the gauge proper operation?
    • Do you have any recomended design, or guidelines for this design?

    thank you very much

    arnon