BQ28Z560-R1 datasheet(17/60 Pages) TI1

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bq28z560-R1

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SLUSBD3 – APRIL 2013

4. The HOST_DISCONNECT (DSG FET OFF) subcommand—This feature is useful for the system to disable

the discharge FET from the battery pack if it fails to authenticate.

The conditions stated above are ignored if there is charge current flow (body diode protection).

Gas Gauge Control of Charge FET

Firmware Control of Charge FET for Protection

The gas gauge firmware control of the charge FET is achieved by using the GPIO with external circuitry.

Typically the COUT pin is high and so to override this, the GPIO pin transitions low and the CHG FET gate drive

is pulled low to turn OFF the Charge FET. The output of the GPIO pin will be released once the fault condition is

removed.

The following parameters can be controlled through firmware (GPIO pin) providing the set thresholds are within

the range of the hardware limits set by the protector.

1. BATHI—Overvoltage protection using COV settings. If the cell voltage exceeds the firmware setting the

GPIO output transitions low to turn off the Charge FET. The Charge FET is turned back on once the cell

voltage decays below the set hysteresis (GPIO output transitions high).

2. OCC condition—If the average current is greater than the set OCC current, the GPIO output transitions low

to turn of the Charge FET. The Charge FET is turned back on once the average current decreases to the set

level.

3. OTC condition—The CFET output will transition low if the charge current is flowing and the temperature is

above the set OTC threshold or Charge Inhibit Temperature Hi. Alternatively, the CFET will not be allowed to

turn ON if the temperature is above the set OTC or Charge Inhibit Temperature Hi thresholds and charge

inhibit flag is set.

The conditions stated above are ignored if there is discharge current flow (body diode protection).

4. Taper Current (TC) condition—This condition can also be used to turn OFF the Charge FET when the

[ChgFetTerm]bit (Bit 2/0x04) in Operation Configuration C is set and the gauge detects primary charge

termination. The CHG FET would turn ON once RSOC < TCA clear%.

Zero Voltage Charging

When the cell voltage is 0 V and if the charger voltage is above the minimum operating voltage for 0 V charging

(1.2 V max), the COUT output transitions to a high level and charge current can flow.

FET Control Protection

Figure 6 shows an overview of the FET Control Protection operation.

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