BQ51051B: Confused while selecting the Coil

Hello

The procedure for measuring and calculating series and parallel capacitors can be found in datasheet "Series and Parallel Resonant Capacitor Selection" 

Also see:

How Do I Select Capacitor Values for a Wireless Power RX Coil?: https://e2e.ti.com/support/power-management/f/196/t/905132

Thank you for your reply, I am calculating the values according to this but but I am confused about the variables.

Because in the datasheet tehere is some random values of 16uH coil. and there not any recommended coil given.

I am confused about the values of fs and fd and Ls and L's.

Below is the link of 47uH coil which I am using I want to calculate the values according to this coil.

Coil Datasheet

Here are the electrical specifications of the coil

where from my guess

fs = 125KHz

and fd = 8 MHz

Please guide me and correct me where I am wrong.

Regards

Rajbir

Hi Rajbir

fs=100 kHz  fd=1 MHz, see datasheet

Ls' -- is a measurement of the RX coil L simulating the coil be on the TX, typically higher than Ls. 

Ls -- is a measurement of the RX coil L in free space, not on TX.

For Ls=16uH with Ls'=17.6uH (estimate 10% increase)  C1 = 144nF C2 = 1600pF

For Ls=47uH with Ls'=51.7uH (estimate 10% increase) C1 = 50nF C2 = 540pF

Bill Johns said:

fs=100 kHz  fd=1 MHz, see datasheet

I have checked that but I thought it depends upon the datasheet of the coil.

Thank you for this,

So I am designing circuit using this IC, so please help me with the values of other components.

Is any other values depend upon the coil.

I am following the circuit above, is there any component depend upon the coil or should I use the values given in the datasheet.

or please help me with the BOM if there any changes according to the coil I am using.

And I am not using any MCU with this.

Also I am confused with the Tri-State and Bi-State pins, what should I do with them.

Regards

Rajbir

Hello

What can you tell me about your requirements, size of battery and charging time?

We may have a reference design that can be used as a starting point.

Hello Bill, Sorry for late reply.

Battery size I think around 350-600 mah and charging time we can accepts 1C or even 0.5C also

Regards

Rajbir

Hello

Take a look at TIDA-00318, very good for low current charging and termination.

https://www.ti.com/tool/TIDA-00318

Also 

TIDA-0669 is a higher current design with additional circuits you may want to consider. 

NOTE -- the coil L value is low recommend using Wurth 760308103215

www.ti.com/.../TIDA-00669

Thank you for this.

Actually the problem is I have bought the 15 peices of 760308101303 Wurth coil and I want to use bq51050B because this is available in VQFN package which is easy to solder. so I want solution to that will solve my problem.

So Could please let me know the BOM with this coil and IC.

And the main problem is our product design can support maximum 30 mm Diameter of the coil and 

Bill Johns said:

Wurth 760308103215

and this one has 48 mm Length which is not suitable for us. 

Please let me know any solution for this or any coil less than 30 mm dia which is suitable for bq51050B.

Regards 

Rajbir

Hello Rajbir

The 760308101303 ( 30 mm and 47uh ) the smaller diameter is offset by the larger L value which is good.  The DCR is high and it will work best at lower currents, say 200mA.

Alright, I am sharing the Schematic below, pleae let me know if any corrections required

The coil I am using here is 760308101303 47uH.

.Base_PCB.pdf

Regards

Rajbir

Looks OK, would be a good starting point.

I am confused about the discrete components values, Are they correct?

Which values are you concerned with?  

I am concerened with the values which depends upon the coil value, other i think are same given in the datasheet