BQ40Z50-R3-DEVICE-FW: Feature Clarification

Hello Jack,

1. May I know the reason why default recovery value is set to 100mA?

For the over-charging current protection. You can see the trip and recovery conditions in Section 2.19 of the Technical Reference. I believe that should clarify your doubts. Basically, once the Measured Current becomes > Requested Current + CHGC Threshold for CHGC Delay seconds, the device stops charging. Recovery is designed to recover during a discharge event, once the Measured Current becomes <  CHGC Recovery Threshold for CHGC Recovery Delay seconds, the device will recover. 

2. Please help me to understand the reason why Ra Filter should be set to 50% when [RSOC_CONV] is set to 1. 

You made a mistake, when RSOC_CONV is set to 1, the Ra Filter should be set to 80%, not 50%. As to why this is the case, it is to make full use of RSOC_CONV. This feature is used to prevent SoC jumps, specially SoC jumps to 0 at terminate voltage, which could affect gauge behavior. It uses "Fast Resistance Scaling" that is based on frequent discharge simulations close to end of discharge. The gauge will calculate a resistance scaling factor for each discharge simulation on the mismatch between measured voltage and simulated voltage(Which is a function of DoD, OCV, R and Temp). This feature requires a Ra filter of 80% in order for the feature to have the desirable impact on the resistance scaling. 

3. Please help me to understand why [RSOC_HOLD] should not be used when [SMMOTH] is set. Is there any effect on the gauge behavior?

The SMOOTH feature controls a complex algorithm that is intended to avoid jumping in the gauge results. This was not designed to work witth RSOC_HOLD, which is used to prevent gauging results such as RM and SoC from changing after charge termination up to when discharge starts. So it isn't recommended to use both together.

Best Regards,

Luis Hernandez Salomon

Hello Jack,

1. Once the protection is triggered, then CHG FET is off. There will not be any charging current, which means setting 10mA or 100mA for recovery threshold is the same.

Yes, you are right. I believe there is a mistake in the Technical Reference, in Section 2.19 it mentions that this recovery threshold value should be negative. So it might be possible that it intended to be -100-mA. I would have to contact others in the team to verify this. Nevertheless, I also think there wouldn't be any difference if it's set 10-mV or 100-mV.

2. Thanks for the explanation. Please correct me if I am wrong. If we set Ra filter to 50% when [RSOC_CONV] is enabled, then it might have a large resistance scaling factor to cause the SOC jump. Is that correct?

At 50% not enough resistance values will be updated to be scaled in order to run the discharge simulations that will adjust the RM to a proper value and avoid any SoC jumps to 0. From my understanding it essentially needs 80% for the Ra scales to be updated properly.

3. Thanks for the explanation. Would you mind to provide me a potential cause if we enable both SMOOTH feature and RSOC_HOLD feature? Thanks.

I am not too familiar with the SMOOTH algorithm, however, because RSOC_HOLD prevents any changes to RM and SoC after charge termination. I am assuming that this interferes with the calculations in the algorithm after charge termination. I can talk with others in the team to clarify this if you need it.

Best Regards,

Luis Hernandez Salomon

Hello Jack,

I've confirmed with another colleague in the team, you should be setting this value negative if you want to use this feature. In the firmware code, it is also set at 100-mA like in the TRM, which it seems to be a mistake.

I've asked to others in the team, there isn't any data to show exactly what would happen if both are enabled. So, we can't really say what will happen. I apologize for that.

Best Regards,

Luis Hernandez Salomon