SLUUBY1B December 2020 – April 2022 BQ76942
The BQ76942 device integrates Overcurrent in Charge Protection (OCC) using a comparator that monitors the differential voltage across the SRP - SRN pins and triggers an OCC alert or fault when the voltage exceeds a programmable threshold VOCC. The VOCC threshold is programmable from 4 mV to 124 mV in 2 mV steps using the Protections:OCC:Threshold configuration register. The OCC protection is enabled using the Settings:Protection:Enabled Protections A:[OCC] configuration bit.
The OCC circuitry triggers an alert signal when an overcurrent in charge event is first detected, then will trigger a fault after a programmable detection delay, OCC_DLY, which can be set from 10 ms to 426 ms in units of 3.3 ms, with the actual delay being 3.3 ms × (2 + setting). The setting 0x0 disables the protection. The delay is set by the Protections:OCC:Delay configuration register.
When an OCC fault is triggered, the device will turn off the CHG FET if configured for autonomous FET control using Settings:Protection:CHG FET Protections A. (the DSG FET may remain enabled if already enabled). The device will recover (if configured for autonomous recovery) when the voltage measured on the PACK pin falls at least Protections:OCC:PACK-TOS Delta below the voltage measured at the top-of-stack for a duration of Protections:Recovery:Time, or a current less than or equal to Protections:OCC:Recovery Threshold (that is, a discharge current) is present for a duration of Protections:Recovery:Time.
Further detail is described in the table below.
Status | Condition | Action |
---|---|---|
Normal | VSRP - VSRN = setting selected by Protections:OCC:Threshold | Safety Alert A()[OCC] = 0 |
Alert | VSRP - VSRN > setting selected by Protections:OCC:Threshold | Safety Alert A()[OCC] = 1 |
Trip | VSRP - VSRN > setting selected by Protections:OCC:Threshold for Protections:OCC:Delay duration | Safety Alert A()[OCC] = 0 Safety Status A()[OCC] = 1 Alarm Raw Status()[XCHG] = 1 if autonomous FET control is enabled |
Recovery (charger detached) | Safety Status A()[OCC] = 1 and PACK Voltage() = Stack Voltage() - Protections:OCC:PACK-TOS Delta or CC1 Current = Protections:OCC:Recovery Threshold for Protections:Recovery:Time duration. | Safety Status A()[OCC] = 0 Alarm Raw Status()[XCHG] = 0 if autonomous FET control is enabled |