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Transmission problem

Rickard Hedlund
Prodigy 20 points
Other Parts Discussed in Thread: BQ51013BEVM-764, BQ51013B

Hi,

I recently acquired bq500211AEVM-210 and BQ51013BEVM-764 but they doesn't seem to be working.

I've connected the transmitter to a DC-source that supplies 5V and around 35mA to the transmitter and diode D1 glows.
TP1 is connected to an oscilloscope, which shows the pulses that are described in the user guide.

The receiver is connected via J3 and J4 to a variable resistor set to 5 Ohms.

I place the receiver on top of the transmitter and make sure the coils are aligned, then I wait for something to happen but nothing happens.
I check TP1 and it's still giving of the same pulses as without receiver.
I do some measurements on the receiver at TP2 and TP4 and they confirm that the transmitter is sending pulses.
There's no output power from the receiver and only diode D1 glows on the transmitter, all the other diodes on the receiver and transmitter are dark.
The transmitter continues to draw the same amount of power as before (5V, 35mA).

I've checked the settings on the receiver before I started testing and they are correct.
The jumpers are set according to datasheet, and I've measured the resistors R3 and R16 and they are set to the right value according to the datasheet.
I've tested the variable resistor and it's working and it can handle the power that the receiver can output.

I don't know what else I can do, everything indicates that the "handshake" between the units fail but I can't find what's wrong.

  • 0
    TI__Guru* 75656 points

    Sorry to hear you are having problems with the two EVMs.

     

    It does sound like a handshake issue but not sure which side is at fault.

     

    Every 400mS the TX will send a very short pulse (Analog Ping) to check for an RX on the pad—note the ping amplitude must change to trigger digital ping, RX position must change.  When the RX is first placed on the charging pad the analog ping amplitude will change and TX will send digital ping. But if TX does not receive a reply it will go back to standby and analog ping.

    Every 5 Sec the TX will send a longer pulse(Digital Ping) to power an RX if it is on the pad.( and analog ping missed it).  During digital ping the RX will power up and reply with Signal Strength, ID and Configuration Packet.  See Figure 5 in bq51013B User’s Guide.  Vrect – TP12 is a good place to look, you should see voltage rise above UVLO, 2.7V then see the first three packets.  Followed by unit transition to power transfer mode and Vrect increasing to target voltage of 7.4V before turning on 5V output regulator.

     

     

    A couple of things to check.

    1.) Make sure the 5V power supply voltage is not dropping during digital ping.

               

    2.) The RX coil may have a high Q and possible have trouble tuning the Vrect voltage to 7.4V target voltage, unit will stop power transfer before 5V output turns ON.  Try loading Vrect ( TP12 and TP14) with a 1K resistor to dampen the circuit.  

     

    3.) Let me know what you see at TP12 if none of the above works, it will give me a clue what is going wrong.

  • 0 in reply to Bill Johns
    Prodigy 20 points

    I've checked all the things you asked me to, unfortunately it didn't solve my problem.

    1.) Make sure the 5V power supply voltage is not dropping during digital ping.

               checked.

    2.) The RX coil may have a high Q and possible have trouble tuning the Vrect voltage to 7.4V target voltage, unit will stop power transfer before 5V output turns ON.  Try loading Vrect ( TP12 and TP14) with a 1K resistor to dampen the circuit.  

                checked, made no difference.

    3.) Let me know what you see at TP12 if none of the above works, it will give me a clue what is going wrong.

               RX TP12 is a flat line no matter what I do.

    I've checked all TP that have hocks on both TX and RX, they're all flat except;
    TX: TP1 TP8 TP15
    RX: TP2 TP3 TP4 TP5 TP6 TP8 TP9 TP11

    All images are taken with RX on top of TX with aligned coils.

    TX TP1

    TX TP8

    TX TP15

    All RX TP that aren't flat shows the exact same line so I only include one