bq51013EVM-725 Wired charging (AD) problem

Radoslav,

My first suggestion would be to switch to the bq51013BEVM-764.  It's a newer device (bq51013B) with several enhancements - and will work anywhere the bq51013 (without the B) would work.  The bq51013 is Not Recommended for New Designs (NRND).

What transmitter are you using?

When a voltage greater than 3.6V is seen by AD, the bq51013 turns off wireless power and turns the bypass FET on.  The AD pin has an absolute voltage rating of 30V so I do not believe that would be an issue.  EN1 = EN2 = 0V enables this function.  Once the voltage on the J1 node is removed, wireless power should be re-enabled. See the datasheet for the modes based on the states of EN1 and EN2.  The absolute voltage on the OUT pin is 20V.  Voltage transients could definitely cause problems so beware of that. 

I cannot find the capacitor ratings for the bq51013EVM-725.  If they are not high enough, that could be an issue.  The bq51013BEVM-764 rates those capacitors at 50V.  I expect they are similar on your EVM.

I suggest looking at a couple of nodes without the voltage at J1.  Look at RECT as this will tell you if the internal rectifier is working.  It should begin to rise in voltage when the EVM is placed on the transmitter.  This is best to look on an oscilloscope.  Measure the VTSB voltage as well.  

Regards,

Dick

Hello,

For the transmitter I use BQ500110EVM-688.

So, when I place the receiver on the transmitter the charging doesnt start, i.e. the red lamp is still on at the transmitter and there is no any voltage induced at the output of the receiver (I measure 0.1 V).

When I observe RECT I can see a peak every 5 seconds (I guess this is the transmitter trying to establish the connection). Inside the 5 seconds interval there are small peaks every 0.4s and voltage is dropping to 0 periodicaly every 0.4s.

None of the combinations of switches EN1 and EN2 changes anything.

AD-EN voltage is always zero, also the VTSB. So i cant really test whats wrong because the power transfer is never established.

If the transistors or capacitors on wired charging branch are burned, that shouldnt influence the wireless charging unless the chip doesnt work.

Do you have some suggestions? Is there an easy way to check which component doesnt work?

Thanks for help,

Radoslav  

Also, I did some measurements with the wired charger and it doesnt make much sense.

When I put EN2 to HIGH (which disables the wired charger) I still get the same voltage as the input one at both RECT and OUT. This is weird, there shouldnt be any voltage at RECT, no?

If EN2 is LOW as it should be for wired charging RECT is 0V and OUT stays the same as input one.

Radoslav,

The DC input voltage should never appear on the RECT pin.  Since your data shows that it does, that indicates a damaged IC.  I would suggest replacing the bq51013.

As the original post suggests,  you should consider moving to the bq51013B.

The previous post indicates that RECT starts to turn on during wireless "ping" events.  You are correct that this indicates the attempt is made to turn on, but that no communication occurs.  In a good device, with good coupling, when RECT is above UVLO, the device will begin communication. Since this does not occur, that indicates damage.

Regards,

Dick

Regards,

Dick

Hello,

Thanks for help, I will consider changing IC or buying another demokit.

This demokit I use only for testing. I will manufacture the TIDA-00318 low power design that is available on your website, since I am interested in low power application. The charging current I intend to have is 35 mA, so is it ok if I only change the corresponding resistances to set this. 00318 design is for 135 mA charging current

I will also produce the BQ51050B PCB since it includes the charger also.

With both of these I intend to use the small TDK coil which is available on the market:

http://product.tdk.com/en/catalog/datasheets/wr_rx-coil-wpr_wr303050-15f5-g_en.pdf

Is there a need do adjust the c1-c13 capacitances for this coil? Because in designs I saw at the website, the same values are usually used for any coil.

Thanks a lot,

Radoslav