BQ76952: Configuration for short circuit

Hello Arjun,

Can you describe what is not working exactly? What is your test procedure, please list your steps.

Best Regards,

Luis Hernandez Salomon

Hi Luis,

If the above configuration is ok for host controlled -short circuit then an interrupt is not coming or you can say BQ not getting interrupt on ALERT pin.

The output for short circuit we used currently is Capacitance bank and when we connect it then huge current up's and down but BQ not getting ALERT on that time. We monitor this on oscilloscope (no waveform is occurring) and the both MOSFET (chg and dschg) is ON on that time.

Kindly share me the configuration for Host controlled short circuit with BQ 

Hi Luis,

Our Application requirement is to get an interrupt at ALERT pin when Short circuit detected. In all other fault we should not get any other interrupt.

We are doing following settings steps by steps->

1. We are configuring ALERT pin config by writing 0x2A. ,

2. We are setting Short circuit Enable by writing in Enabled Protection A  0x80

3. We are setting default mask alert (SSA) 0x4000.

4. We are setting SF Mask Alert A 0x80.

5. We are setting Short circuit detection threshold 7, (150 Amp). @ 1mohm shunt resistor

6. We are setting Short circuit detection delay  15 us.

7. We are setting Short circuit detection recovery time 20s.

Testing Method->

We are connecting a large capacitor bank 50k-75k uF.

Observation->

Our ALERT pin is low , after short circuit detection ALERT Pin consistently high.

a.) How to reset ALERT Pin ?

b.) please suggest what are we missing in our setting procedures.

Hello Arjun,

Understood. So this sounds like everything is working correctly and you just want to know how to reset the ALERT pin, correct?

In this case, the bits in the AlarmStatus (0x62) register are latched and the ALERT pin will stay asserted until these bits are cleared. You can clear the corresponding bit by writing a '1' to that bit in the AlarmStatus register. This is described in Section 6.6 ALERT Pin Operation of the Technical Reference Manual.

Best Regards,

Luis Hernandez Salomon

Hi Luis,

Now I am facing further problem after short circuit recovery BQ (I2C Communication) break/looks like HANG and I checked from MCU side communication is working from CRO. 

Please suggest in which conditions of I2C communication can break/Hang from AFE Bq76952 side.

Hi Luis,

After Short circuit recovery BQ not update the following values- Voltage, Current and temperature. 

I have tried to reset the BQ via BQ_RESET sub-command but the values of current, voltage, temperature not updating.

Please suggest me the root cause of this situation and also suggest the possible solution.

Hello Arjun,

Do communications recover after power cycling the device? If you send 8 clock signals, do communications recover? What is the REG18 voltage?

Do you have any logic analyzer captures? 

Best Regards,

Luis Hernandez Salomon

Hi Luis,

Yes, Communication is recover after power cycling the device and MCU sends 8 clock signals. 1.8V I checked on REG18.

Hi Luis,

We have facing problem with following condition-->

When Short circuit happened ( Enabled Protection A  0x80 ; default mask alert (SSA) 0x4000 ; SF Mask Alert A 0x80 ; Short circuit detection threshold 7, (150 Amp) ; Short circuit detection delay  6 (75 us) ; Short circuit detection recovery time 20s)

1). On ALERT Pin interrupt is received ( ALERT pin config  0x2A ), then Both Power MOSFET is switched OFF through Host Microcontroller.

2). Clear all short circuit flags ( Enter Config mode (SET_CONFIGUPDATE) ; default mask alert (SSA) 0x4000 ; Exit Config mode      (EXIT_CONFIGUPDATE))

again short circuit happened again both STEPS 1 and 2 proceeds.

After recovery 

Observation/Problem we faced.

1).  All measurements like, Cell voltages, temperatures and current stops. (Probably ADC SCAN STOPS).

NOTE:-->  ALL Power supply is Live 

                 REG18 (1.8V) is Live

                 REG1 (3.3V) is Live

We request you to please suggest what mistakes we are doing?

Hello Arjun,

I do not believe you have to enter CONFIG_UPDATE mode when clearing the short-circuit flags. 

Usually in config update mode the part stops all measurements completely and turn-offs both FETs during this mode.

If you send the 8 clock signals during this time, can you communicate again?

Can you try the procedure without entering CONFIG_UPDATE mode?

Best Regards,

Luis Hernandez Salomon

Hi Luis,

I2C communication is in order.

We are unable to find the procedure without entering CONFIG_UPDATE mode to reset the ALERT Pin in datasheet as well as in Technical reference manual.

We request you to please suggest the procedure how to do it ?

Hi Luis,

Thank you for the support and quick reply.

Now short circuit is happening properly but now the current problem is after power on the BQ  and BQ reset by hardware an initial interrupt  is coming on ALERT Pin for about 85us and gone.

How to resolve this problem ? Kindly suggest me.

Note- there is no load or no current is applied on BQ power on .

Hello Arjun,

Glad to hear short-circuit protection is now working correctly .

Can you clarify? I do not understand this portion "after power on the BQ  and BQ reset by hardware an initial interrupt".

What is going here? Can you list in steps what you are seeing?

Best Regards,

Luis Hernandez Salomon