Hello,
We've noticed a strange behavior on our PCBs implementing the BQ25895.
We have the exact same part (same schematic) on another design and it works fine.
When the charge is near the end, instead of simply reaching termination and stopping the charge, the charge current oscillates between 0 and its previous value. When we poll the resgisters, they also oscillate between "Charge done" and "Fast charging". The oscillation rate is fast, possibly around 100 Hz. This is also visible with the /STAT LED blinking quickly instead of just turning off after the charge.
Please find attached a screenshot of the battery voltage (purple, V), battery current (green mA), and a calculation of the average current (orange, mA), where you can clearly see the oscillation at the end.
This is with all the parameters at the default value (except the watchdog that is disabled).
When we increase or decrease the Termination Current Limit (REG05:0-1-2-3), the oscilaltion occurs shortly after the selected current.
Here's the register dump:
w D4 00 7F #Input Current Limit, HIZ and ILIM pin
w D4 01 05 #OTG Temperature thresholds, and Input Voltage DPM Offset
w D4 02 3D #ADC controls, OTG Frequency, ICO, DCP, and Input Detection
w D4 03 3A #Battery Load, WDT Reset periods, OTG and Charge Enable, and MINSYS setting
w D4 04 20 #Fast Charge Current Limit settings and MTK Pump enable
w D4 05 10 #Pre-charge and Termination Current Limit settings
w D4 06 5E #Charge Voltage Regulation Limit, Battery Low Voltage and Recharge threshold
w D4 07 8D #Termination Current Enable, STAT pin, WDT, Safety Timer, and JEITA Charge Current
w D4 08 03 #IR Compensation and Thermal Regulation thresholds
w D4 09 44 #ICO, Extended Safety Timer, BATFET control, MTK Pump Voltage, and JEITA Charge Voltage
w D4 0A 93 #OTG Regulation Voltage and Current Limit settings
w D4 0B 76 #Charger VBUS, Charging Mode, PG, USB Input, and System Voltage Regulation status
w D4 0C 00 #WDT, OTG/VBUS OVP, Thermal Shutdown, Safety Timer, and TS pin faults
w D4 0D 12 #Input Voltage DPM settings
w D4 0E 52 #Thermal Regulation Charge Status, and ADC Battery Voltage conversion
w D4 0F 52 #ADC System Voltage conversion
w D4 10 47 #ADC TS pin voltage as percentage of REGN conversion
w D4 11 93 #VBUS status, and ADC VBUS Voltage conversion
w D4 12 0E #ADC Charge Current conversion
w D4 13 4D #DPM status, and Input Current Limit setting
w D4 14 79 #Registers reset, Input Current Optimizer status, Device ID, and Temperature Profile
Any ideas? I looked at this thread but the conclusion was that their watchodg was reseting the charger, which is not our case. https://e2e.ti.com/support/power-management-group/power-management/f/power-management-forum/942255/bq25895-charge-state-oscillation-near-the-end-of-charge?tisearch=e2e-sitesearch&keymatch=bq25895%25252525252520termination#
Thank you
