bq24202 stat pin status

Hi Giovanni,

What is the voltage at BAT pin?

Can you send a scope picture of BAT, STAT, OUT, and TS?

Thanks!

Tahar  

Dear Tahar,

the voltage at Vin pin, which is connected to the Vcc pin through a 10ohm resistor, is at 12,6V.

When Vin is at 12V,6, Voltage at STAT pin switches from oV to 12,6V; voltage at BAT pin switches from 3,7/3,8V to 4,2V.

I do not have a TS pin.

It seems like STAT and BAT pin are switching not in synchro each other: can't supply a picture of the scope because I have an old analog one.

If needed, I could make a short movie... let me know.

The BQ24202 is hot, i.e. I can't leave my finger on it.

Hope to hear from you soon, and hope everything is fine ;)

bye

Giovanni

Hi

If you are not using the TS pin, you need to disable it by applying a voltage between VTS1 and VTS2.  Please see the datasheet for more info on the temperature sensing feature.   

Can you please verify you schematic with our EVM user’s guide schematic?

http://focus.ti.com/general/docs/lit/getliterature.tsp?literatureNumber=sluu107&fileType=pdf

Do you have our EVM?

Thanks

-Tahar

Hello,

I did not find a TS pin on datasheet for the BQ24202.

Are we talking about the same IC?

Hi Giovanni

If you are using the bq24202 version, instead of the TS pin, it is replaced by the CE pin and that should be enabled. Please verify your schematic with our EVM Schematic.

Thanks

-Tahar

Dear Tahar,

when Vin is present, and higher then 5V, CE pin is ALWAYS at low level.

I built a small circuit around the ICL7665, voltage supervisor, which switches CE at low level when Vin is present and higher than 5V.

Is it possible to always leave CE at low level, when Mains (Vin) is present?

Maybe I have to switch CE low only when battery is discharged, and to pull it high when battery is full?

Do I have to check for battery status by a dedicated hardware? if so, my schematic is bad and I have to build a new one.

The behavior described above was showing when battery was almost full: since this morning, after I discharged it a little, when Vin is present I see a current of about 100mA

flowing from Vin through to the battery; to experience that behavior again I have to charge the battery at the highest level... I will let you know.

Hope to hear from you soon.

Giovanni

Hi

The CE pin is used for enabling and disabling the part. If the part operates properly and enabled, it should behave as shown in figure 6 in the datasheet. Your supervisor should not cause the issue.

The BAT pin is used to sense the battery voltage and determines the status of the battery voltage. It should not switch between 3.7 to 4.2V. Based on the STAT pin indication, it looks like your battery is going from Fast Charge to Charge Compete.

Can you try to charge up your battery to full charge using a power supply and see if it has the same behavior?   

Please verify your schematic and the layout with our user’s guide and see what are you doing different.

Also, you can order our EVM and try it in your battery.

Thanks

-Tahar

Hello,

the main difference between EVM and my circuit is in EVM CE/TS pin is connected to the temperature sensor of the battery; in my circuit, CE is handled by hard-wired logic,

and usually when main supply is present, is at low level.

The circuit I used is reported on first page of SLUS501C–OCTOBER 2001–REVISED MARCH 2008 (bq2420X datasheet).

Also, battery I am using does not have a temperature sensor!!

Could this help solving the problem?

thanks

Giovanni

HELP!

Hello,

I would like to receive an answer to the following question: is the circuit reported on first page of SLUS501C–OCTOBER 2001–REVISED MARCH 2008 (bq2420X datasheet) correct?

If yes, why do you always refer to the circuit reported on the EVM? does not it have to work the same way?

If no, I think there is something wrong on that DS which should be corrected ASAP.

Thanks

Giovanni

Hi Giovanni,

The first page on the data sheet in correct. Most of our data sheets we provide a non-detailed typical application circuit. For more detailed information, we develop what we call Evaluation Modules or (EVM). Our customers use the EVM as their reference in the design/debug process. The full schematic, the BOM, the layout, and the test procedure are provided on the user’s guide. The EVM should be available on line for you to order. Hope this answers your second post.

As I said in my previous posts, the bq24202 does not have TS pin but instead the CE pin which should be low to enable the part. If hold high, the part will be disabled.

Please do the following and let me know:

• Did you try to charge your battery using a power supply instead of the charger? See if the issue does not come from the battery itself because some batteries have protection circuits build in and prevent the charger from charging.
• If you have a different battery, try it instead and see if there is ant improvement
• Compare the EVM schematic and the layout with yours and see if you can see any issues and differences that may lead to the root of the issue.
• Order an EVM and test it with your set up  and specs
• If you can take some plots, send them to me so we can have a better understanding of what is going on in your system.

What is the volume of your project?

Thanks!

Tahar

Dear Tahar,

below you will find the schematic I used:

as you can see, I used the configuration reported on the first page of DS, which would just have been enough for my job.

I already built 5 prototype boards containing the configuration reported above; I used the bq24202 because of simplicity.

Deadline for development stage should be the end of current month; than we MUST go in production or stop it.

Because of deadline, I do not have time for EVM testing and, because of simplicity, I do not wish to perform EVM testing.

When in production, we hope to ship at least 100 units/year.

So tomorrow I will perform the tests you requested and will report on this forum.

The battery I used is http://docs-europe.electrocomponents.com/webdocs/0728/0900766b8072846d.pdf

Thank you for your support.

Giovanni

PS. After looking more in depth at battery DS I am going to think battery could not be right: tomorrow I will try to replace it.

Hi Giovanni,

Your schematic looks good to me. Make sure your BOM and your layout are checked out too.

For the battery, I am not really familiar with this type of batteries.

Can you please update me of your findings as you go?

Thanks!

Tahar

Dear Tahar,

this morning I performed a complete test with a cell phone Li-ion battery.

So, when I switched the system up, for the first 30 seconds the stat pin switched on and off, with the charge current coming from 10mA to 150mA and back again.

After 30 seconds, the current stabilized at 100mA about; then current slowly descended to 10mA and less, leaving the battery at 4,3Vcc.

I am going to think the problem depends on the battery I used first, which is not a cell phone battery, is not it?

bye

-g

Hi Giovanni,

It sounds like the issue is from the battery. You can contact the battery manufactorer to provide you with more info about the battery. Also, see the protection circuit of the battery that may be interrupting the proper operation of the battery during the charging process.

Thanks!

Tahar

Hi Tahar, I agree with you.

Did you take a look at the battery datasheet I reported in previous message?

Could I use that kind of battery with BQ24202?

Bye

-g