Wireless receiver BQ51050B

Hello,

I'm not sure what is the TX coil are you using, is it a standard TX coil? 10mm RX coil will not work with a standard TX coil as it is too small. I suggest you start with using a larger RX coil and the tune Cs/Cd.

Thanks,

Wenjia

HI Wenjia,

Thank you for reply.

We are using wireless transmitter Qi1.1 compliant AEP-5000WP  which is used to charge smartphones. Here i have attached picture showing relative coil dimensions.

As we have mechanical constraint, we have to use smaller sized coil.

We measured Fs across both Tx & Rx coils when magnetically coupled, get same Fs = 174KHz.(which is within range of 110-205KHz)

In our design, we used capacitive load modulation for COM1 and COM2 pins.

For your ref, values of discretes (terminology used as per Datasheet) =>

C1 or Cs=47nF 50V , C2 or Cp=2.2nF 50V

Cclamp1 & Cclamp2 = 0.47uF 50V

Cboot1& Cboot2 = 10nF 50V

Ccomm1 & Ccomm2 = 22nF 100V

To establish communication bet Tx & Rx coil, kindly suggest which Ccomm values to be set.

Regards,

Hardik Dhameliya

Hardik,

The 10mm coil will not work wit the standard size TX coils. We just had it working once in the lab, but we were using the 20mm TX coil. If there is size constraint in your application, you can probably try a smaller TX coil. But again, we don't have enough data to guarantee it will work.

Thanks,
Wenjia

Also, you can refer to TIDA-00415 which is using the 20mm coil and has worked with the 10mm RX coil.

http://www.ti.com/tool/tida-00415

Thanks,

Wenjia

Hello Wenjia,

Thanks for kind support.

We have made one single layer circular Rx coil. ( 26mm outer Dia, 18mm inner Dia, 14 turns, single layer, copper wire guage 0.32mm)

and We are able to establish communication between Tx & Rx coil and BQ51050B is giving output.

We are varying distance between Tx & Rx coil, But we are getting communication upto 6.0mm only.

So, how can i increase this distance? as i require it around 10mm.

Regards,

Jay Patel

Jay, 

Generally, 3mm is the maximum Z distance for most of the applications to achieve good coupling and communication. 10 mm is way beyond the spec and it is very hard to increase the distance. Changing COMM caps maybe one thing you can try but there's no guarantee with this big Z-distance.

Thanks,

Wenjia 

Hi Wenjia,
Thank you for reply.

With the help of coil, (same Dimensions - 26mm outer Dia, 18mm inner Dia, 14 turns, copper wire guage 0.32mm )
We are able to get communication and power transfer between Tx and Rx coils.

For single layer coil, we are getting communication+power transfer upto 6.0mm and
For Double layer coil, we are getting communication+power transfer upto 12.5mm with Ccomm1 = Ccomm2 = 22nF 100V

But as per equation, RILIM = KILIM / Iout --> RILIM = 300/55mA = 5.4545K (chosen value 5.36K 1% 0402)

Still i am getting Battery charging current = 34mA stable. (required is 55mA)

What can be the reason that calculated resistor value is not giving proper charging current?

kindly refer to my another post at e2e.ti.com/.../422612

Jay,

What is our VOUT and IOUT of the RX (in the case of bq24090)? You need to make sure that the input power to the charger is enough to provide whatever you programmed on the output.

Can you also share the schematic?

Thanks,

Wenjia

Hi Wenjia,

Please find above schematic.

Awaiting for the reply.

Jay,

I suspect that the input power is limited so that it cannot provide whatever you programmed at the output. Can you measure the input power of your TX? Also can you measure the frequency of the RX?

With 55mA charging current, your termination current is 5mA which is way to low for bq51050B. At this level it is possible that some of the ICs may not terminate at all. I recommend you to use bq51003+bq25100 to charge the small battery. It can supports termination down to 1mA.

Thanks,
Wenjia