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BQ76PL455A-Q1: How to detect if Charger or Load is connected?

Abhishek Deouskar1
Prodigy 40 points
Part Number: BQ76PL455A-Q1
Other Parts Discussed in Thread: BQ76PL455A

Hello,

I am using the bq76pl455a-q1 to develop a battery management solution and I have a few power MOSFETs to control the charging and discharging circuits. 

I am however not sure how to develop a charge/discharge detection circuit using Hardware which gives a software input to the bq76pl455a_q1/MCU in some form saying, "Hey, I am here, Let's start charging or discharging, shall we?".

At this point, I do not have control over which Charger or Load is connected and have to work off non-smart charging/discharging techniques. 

A start point would be welcome. 

The following assumptions can be made: I also have an MCU with GPIOs, ADCs, Timers, and other things. I also have Current Sense resistors in place which can be rerouted if necessary. 

Thanking You. 

  • 0
    TI__Genius 17370 points

    Hi Abhishek,

    Are you wanting to signal to 455 device that charging is starting or signal to charging ckt? Either way - both are driven by host MCU correct? So once the host MCU decides to drive charging/discharging ckt path, it should also be able to notify 455 device state beforehand etc?

    Regards,

    Taylor

  • 0 in reply to Taylor Vogt
    Prodigy 40 points

    Hello Taylor,

    I am looking to signal the MCU that a Charger is detected. The MCU has complete control over the Charging circuit, as in turning it ON and OFF, as well as the current flow (using PWM). However, only issue I have been unable to resolve is how to detect if the Charger is present or not. Some ideas I came up with are:

    1. Use a similar concept of Window Comparator as used in the pl455 with Vref as Battery Voltage and the Input as the Charger Voltage. If the Vin is greater than Vref, then the MCU is intimated that a charger is connected. However, an Opamps usually require dual supplies and Bat Voltages and Charger Voltages are high, so cost of that circuitry is an issue.
    2. I can translate the Charger Voltage via a Potential divider and feed it to an ADC either on the pl455 AUX channels. This way I can use the AUX threshold limits on the pl455 to trigger an output on one of the GPIO pins, but I think there is still an involvement required by the MCU to do some processing. And also I don't just need to turn the mosfets ON or OFF, but also have controlled current flow (PWM), which is easier to do with the MCU. I can also feed the translated voltage into an MCU ADC. However, overall I am worried about the heat dissipation due to such a major step down in Voltage. 
    3. I am using only 14 channels of the pl455. I can add the charger voltage at SENSE15 and keep checking when it goes above 0. 

    These are some ideas just off the top of my mind. However, you are best suited to give me a start in the right direction. 

    Thanks.

  • 0 in reply to Abhishek Deouskar1
    TI__Genius 17370 points

    Hi Abhishek,

    I would suggest rather a switch that triggers GPIO input or a pin on the MCU to indicate charging ckt is activated. But this would ultimately be up to you - it is not something the bq device would control that I could provide great support for.

    Regards,

    Taylor