Failure to re-initiate charge when connected to transmitter.

Francesca,

When the bq500210 receives the charge complete signal, it will not attempt to restart for 5 minutes (see section ADVANCED CHARGE INDICATION SCHEMES in the datasheet). Have you verified the 5 minutes has expired? Each time the timer expires, it will power the receiver up and if it receives the same charge complete message, it will shut down for an additional 5 minutes.

Regards,

Dick

Thank you for the response Dick. 

I have verified it does not re-initiate after 5 minutes however, the green solid light indicates it was not a fault but a EPT event that ended it, based on my understanding of the LED scheme on the BQ500210EVM-689.

When reading additionally into the Qi protocols, section 5.1.2.1 "Selection" from the Tx perspective:

"If a Power Receiver has made at most three unsuccessful attempts to initiate and maintain a power transfer, the Power Transmitter shall refrain from entering the ping phase until the Power Receiver has been removed from the Interface Surface of the Base Station. An example of an unsuccessful attempt is when the Power Receiver has terminated the power transfer three times in a row with an End Power Transfer Packet containing an End Power Transfer Code of 0x08 (No Response) or 0x0A (Negotiation Failure)."

If after 5 minutes, it comes back and the first packet it recieves is an EPT, theoretically is it again supposed to wait 5 minutes and come back? 

What I am seeing is after the battery voltage increases to 4.2V, there are 3 packets sent and then V-RECT drops and the device no longer charges, as shown in the above scope shot. In looking at these packets I am finding it challenging to parse out the data, as there does not seem to be a clear description of how many preamble bits there is (there appears to be 22). One packet was clipped however the other two both appear to be Preamble (22 bits) Header  (0x02) Message (0x00) Checksum (0x00) [1111111111111111111111 01100000011 00000000011 01100000011].

From this I gather that I am receiving an EPT signal for an AD > 3.8V however, /AD is grounded and /AD-EN is N.C.. After three of these occur, the PTx disconnects. If the coil is removed and replaced, it successfully reconnects and initiates power transfer for a battery level under 4.2V. 

I am using a power supply as a battery simulator, but we have seen the same results with 4.2V LiPo batteries as well. 

Ultimately what I would like is for the coil to be placed on the charger and stop charging when complete @ 4.2V, and start charging again when the battery level falls below ~4.2V if it remains on the charger and in use. Right now, my application is terminating power transfer on the Tx and not resuming as the power drops, thus coming off of the charger with sometimes less battery level than when it went on (the applciation is being used on the charger and is drawing normal current amount). 

From what I have described, do you have any advice as to a possible design flaw I may have made on the Rx circuit end that may be causing this? 

Thank you, 

Francesca

I will work with you off line on this problem.