BQ76905EVM: FET Control configuration

Hello Pranav,

Pranav M said:

Observation :

1. OCD1, OCD2 and SCD  Discharge mosfet disconnection successful.

2. If Current reduces below OCD2: Discharge mosfet Re-connection successful

3. If host wants to disconnect & reconnect the mosfet for other protection, it FAILS.

If you want to control the disconnect/reconnect of the MOSFETs, you need to enable the Settings:Configuration:FET Options[HOST_FETOFF_EN] and Settings:Configuration:FET Options[HOST_FETON_EN] bits. You mentioned you have 0b000 0110, which seems you do not have these bits set. So you cannot control the FETs with host commands.

Pranav M said:

1. SCD Discharge mosfet disconnection successful.

2. If Current reduces below SCD: Discharge mosfet Re-connects!! even though current is in  OCD1 and OCD2 range.

Are the protections triggered? Can you provide details on the test, the protections triggered during and after the test?

Can you provide the .gg file so I can look at your settings?

Best Regards,

Luis Hernandez Salomon

> Are the protections triggered? Can you provide details on the test, the protections triggered during and after the test?

> Can you provide the .gg file so I can look at your settings?

I do not have .gg file, as we are communicating with AFE via host controller over I2C.

Yes, protections are getting triggered, but discharging mosfet is not disconnected, only SS alert bit in battery status register is set.

Below is the configuration made to enable OCD1, OCD2 & SCD protection DSG Disconnection:

FET Options : 0x901E : 0b0011 0110

Enabled Protections A : 0x9024: 0b0011 1000

OCD1: 0x9038: 0x1E

OCD2: 0x903A: 0xF

SCD: 0x903C: 0x04

The current is set initially to normal operating range and then gradually increased to OCD2 limit.  Only SS alert bit is set in battery status register and DSG is not disconnected.

As per the data sheet it is mentioned device can work autonomously and manual mode for the selected faults, we have configured for OCD1, OCD2 & SCD fault in AFE for autonomous control, other faults are handled by host controller. 

Please share the correct register settings to configure autonomous AFE control for OCD1, OCD2 & SCD faults.

Rest of the faults to be handled by host controller.

Hello Pranav,

Are you able to communicate with your device using an EVM or EV2400? Having a .gg file would make it easier to understand all your settings.

Now, on what you have written down I will analyze and provide some feedback tomorrow if any!

Best Regards,

Luis Hernandez Salomon

We are working with customized board, where host MCU is interfaced with AFE chip over I2C.we are able communicate with chip and read the Voltage, current and temperature values.

We have only issue while both Host and AFE controlling the FET's as explained in the above post.

Hello Pranav,

As I mentioned earlier, you did not have the HOST control bits set. FET Options : 0x901E : 0b0011 0110 should be 0b0111 0110 if you want to control the FETs with HOST commands.

I think it would be useful if you can provide a log of the registers during this testing. It is hard to know what is going on otherwise. Safety Alerts/Safety Status/Battery Status would all be good to have in the log. Mind also sharing your schematic?

Best Regards,

Luis Hernandez Salomon