Can we increase max discharging current based on BQ77910 design?

The current thresholds are voltage based, so you can extendthe design to higher currents.  The overcurrent threshold for example can be set from 25 to 500 mV. Some areas of consideration in a higher current design might include:

• The value and power rating of the current sense resistor
• FET selection and heat-sinking
• Board and terminal physical construction to handle the current
• Transient protection design to keep the device inputs within the absolute maximum ratings

Hi WM

We have done the above three points you mentioned.  The key point is we do not know to improve the transient protection design eventhough we follow BQ77910 design note.  The chip seems to be dead because there is low voltage output to CHG MOSFET gate after reset.   Can you clarify this point?

Thanks.

Abel

If you are working with an early engineering sample, check any errata that came with it.  Some early device samples did not support the CHG output. If there are questions, please contact your local TI sales representative.

If you have current devices and a part was working but stopped after testing: This sounds simple in a description, but you really have to find the event which is causing the damage, then eliminate its source, or clamp, filter or isolate the IC from the transient. Knowing when it worked and when it stopped and evaluating the testing or events between should help determine where and when to look.

In my testing there are a few usage situations and 3 damage events which may result in no CHG output, there may be others:

• Disconnected cell monitor connection resulting in an open cell fault, but this will also disable DSG
• PACK- is below battery- which forces the VREG on but the part is not 'awake' and does not turn on DSG or CHG.  CHGST must go high to wake the part.
• PACK- remains near PACK+ so the device can't turn on CHG
• Damaged inputs creating a permanent OV
• Output damaged by excessive charge voltage, CPCKN too far below BAT during OV or SCC protection
• Output damage by CPCKN above BAT during OCD/SCD protection

A first step would be to check the BAT voltage is above minimum for operation, CHGST is high and the PACK voltage is near nominal

A second may be to use the GUI to check the device status while CHGST is held high to see if it detects a fault.

Finding a damaging transient can be difficult if the part is damaged before it is found and then can't be re-produced. It may be helpful to inspect signals with a lower power version of the test or by simulating signals from the IC to measure various signals and determine what may be approaching the abs max limits.  Then analyze the circuit to determine what portion of the transient protection needs enhancement in your system.  For very severe environments it may be more effective to use an external FET driver controlled by the IC which may be better able to handle high transients rather than clamp signals to the IC's maximum levels.