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Parasitic Metal Object Detection (PMOD) with bq500210

Frederic Vautard
Prodigy 35 points
Other Parts Discussed in Thread: BQ500210, MSP430G2001

Hi,

We have made a Power transmitter based on bq500210. We are not (yet) using the MSP430G2001 and therefore the LEDs are directly connected to the bq500210. Our power transmitter works very well (tested with bq51013EVM), it has a good detection of the receiver, good efficiency...

The Parasitic Metal Object Detection (PMOD) is setup with a 100K resistor (Threshold of 1200mW) and is able to detect when a small metal object is placed between the transmitter and receiver (the Red LED blinks quickly). If we do not remove the object, after 20 seconds (warning time) the power transfer is stopped (as expected) but instead of being halt for 5 minute (as per what is explained in the datasheet), the power transfer restart again 1~2 seconds later with the green LED blinking for few seconds and Red LED blinking again for 20 seconds. This cycle repeats again and again.

Therefore, the warning (Red LED) is working properly, however as the power transfer restart again, the power is actually never stopped and fail to protect small metal object from overheating. 

Is the 5 minutes halting state a feature of bq500210 or is it related to the MSP430G2001 ? Any idea how to solve this issue ?

Thanks for your help,

Fred.

  • 0
    TI__Guru 67676 points

    Hello Fred

    The MSP430 will hold all status information when the bq500210 goes to sleep and 3.3V is removed from it.  If the MSP430 is not used then power must stay on the bq500210 to hold state info.  One possibility is the sleep circuit is turning off power to the bq500210 after it stops power transfer.  Would you verify that the 3.3V continues to be applied to the bq500210?

     

    Also send me your schematic using the conversation feature of the form.

     

    Bill

  • 0 in reply to Bill Johns
    Prodigy 35 points

    Hi,

    The power is always applied to the bq500210. Moreover normally the MSP430 is reducing the power consumption by putting the bq500210 in Reset mode. In our case the pin 5 (reset) of bq500210 is connected to a RC (280K, 4.7uF) with 3.3V without any MOS transistor to discharge the reset capacitor.

    This issue seems happening with "big" metal objects only, maybe when the power transfer is cut (after the 20 seconds warning time), the communication with the receiver is lost and therefore the bq500210 restart the communication from the beginning...

    Fred.