BQ32000 RTC after power off clock time is stop counting

Naresh,

Just need a little clarification here. 

We don't have a VBAT pin on this device.  Are you talking about "Vback"?  You are connecting 3.6V to Vback and switching off power to "VCC"?  Is this what you are meaning to say?

If you have a schematic, that would also help.

Thanks!

Ryan,

I am having the same problem related. Sometimes that is stuck in power off. After a power off, rtc gives the last datetime at first reading, but at the second reading the rtc gives right datetime as everything is normal. 

I was thinking that it was a feature, but as it happens sometimes so it can be a error.

The schematic:

Do you have any suggestion?

Best Regards,

Just to clarify, "power off" means that VCC goes to 0V, but Vback is at what voltage?  Please give me the voltage reading of Vback.

Are both Y3 and Y4 populated?  C36 and C35 should be removed. 

Ryan,

"Power off" means that VCC goes to 0V. Vback is 3V. Only Y3 is populated.

I will remove C36 and C35.

Best Regards,

Ryan,

I removed C36 and C35, but the problem still happens sometimes. I get some wrong readings.

Do you have any suggestion?

Best Regards,

irfan

put decoupling capacitor from Rtc 8 pin of 0.1uf or 1uf and Vbat  pin grounded with 0.1uf capacitors

Reading back through this post, I am wondering if the following is the problem:

The time keeping registers can take up to 1 second to update after the RTC switches from backup power supply (Vback) to main power supply (Vcc).

If you wait >1 second and then read, is the time normal?

Where you able to verify if this is the issue or not?

Hi Ryan,

We are facing problem of unstable behavior of BQ32000, following is .

 1. We have connected load capacitor of 33pF with crystal in our custom board. Now the RTC is not working with load capacitor in new PCA, after removing the capacitor its start working.  We had populated 33pF capacitor in previous PCA, and it is working fine. Now there is no difference of PCB and BOM in both PCA.

2. We have not enabled trickle charger circuit in driver, although it is charging battery. 

Can you please tell me why RTC IC is misbehaving ? What can be reasons of misbehavior of IC ? 

Viral,

1)  BQ32000 has two internal 24pF capacitors (each terminal to GND), so that it is tuned to a 12pF XTAL. There is no need for external tuning capacitors.  Please remove the 33pF capacitor from your BOM.  I have no idea why it worked before, but it must have been on the edge of functioning. 

2)   I don't see how this is possible.  Please see the top of page 7 in the datasheet. 

All trickle charge switches are opened when the device is initially powered on and each time the device switches from the main supply to the backup supply.  You have to make two register writes to close the switches.  Is your code doing this?

Hi Ryan, 

Thank you very much for your quick response.

Yes we are removing the capacitor from populated boards and from BOM also. We were not touching that trickle charger related register. We are also start changing our RTC driver with battery charging functionality as suggested in datasheet.

Once again thank you for your valuable advice.  

Thanks & Regards

hello friend! You could solve the problem? happens to me the same

Matias,

Please be more specific.  The problem in this thread was solved with my recommendations above.  If you are seeing something different, please let me know. 

Ryan, first excuse me for my bad English.. i'm from Argentina. My problem was the same that had  NARESH PANCHAL when he said: "There is problem facing is RTC time counting stops after power off. Its showing same time what ever at power off time. I tried it by providing power off period for 5minutes, 10 minutes etc. For example I'm switching power at 10:30 and switch on power after 5 minute i.e. 10:35. RTC showing time 10:30 and from this its starts counting. Please suggest any solution for this."

However, I could solve the problem, waiting about 2 second for read the RTC when this switches from backup to power supply..

thank you very much for your attention!

Your english is just fine!! 

Did you try this as posted before?

The time keeping registers can take up to 1 second to update after the RTC switches from backup power supply (Vback) to main power supply (Vcc).

If you wait >1 second and then read, is the time normal?

yes! if I wait more of 1 second (about 2 second) for read the RTC when switches from backup power supply (Vback) to main power supply (Vcc) the time is normal, but if i wait less of 1 second the time is the same which had when power off Vcc. 

Matias,

Thank you!  We are going through a datasheet update now.  I will make sure we check this out thoroughly and get it added to the specification.

you're welcome Ryan! It is a good idea clarify this!!

I was working with the TI components during all my career as an engineer in electronics, and I'm currently working with them controlling DC motors for my tesis. I count on you for any problems! Thank you very much!

Hi Matias,

Checked the functionality of the IC and the register [0] with 0x00.  Used an AARDVARK I2C communicator to commuicate with the BQ32000 device.  The xternal 4.7K pullups on SCL and SDA were  removed and the internal pullup of the AARDAVRK communicator was used instead.

BQ32000, I2C is disbaled when the VCC is removed. In Vback mode,  the registers cannot be readback. However, when the device enters the active mode ( VCC is on ), the registers can be readback with valid data. When reading registers,  make sure, the user issues a WRITE to  the ADDRESS before READing from the ADDRESS; The readback data lenght is 1 byte long.

 the internal counters and registers are all functional and the data is valid as per specification unitl VBACK = 1.4V min(  VCC= off ( 0V)); As per spec description, the OSCillator is also validated  to force STARTs and STOPs.   

txs

vish

Hi Vish! Thank for answer me! My problem have been solved.. The communication between BQ32000 and MSP430G2553 with the protocol I2S is very good and shows no problem.. again, thank you!