BQ28Z560-R1_14 Datasheet, PDF (17/61 Pages) Texas Instruments – Single Cell Li-Ion Battery Gas Gauge

Not Recommended For New Designs
bq28z560-R1
www.ti.com
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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