BQ28Z560-R1_14 Datasheet, PDF (16/61 Pages) Texas Instruments – Single Cell Li-Ion Battery Gas Gauge

bq28z560-R1
Not Recommended For New Designs
SLUSBD3 – APRIL 2013
www.ti.com
Charge Overcurrent Detector
If the voltage across both protection MOSFETs (V_M – V_SS) becomes more negative than the charge overcurrent
detection voltage (V_DET4 = –0.112 V typ) for a period up to the charge overcurrent detection delay time (t_DET4 =
12 ms typ) due to an abnormal charging current or abnormal charging voltage, the bq28z560-R1 detects the
overcurrent charge state of the battery and the COUT pin transitions to a low level. This prohibits charging the
battery by turning off the external charge control N-channel MOSFET. The bq28z560-R1 releases from the
charge overcurrent detection state on by detecting the connection of a load for a period up to the overcharge
release delay time (t_REL4 = 4 ms typ).
Table 2. Hardware Control Due to Fault Detection
Fault Condition DOUT
Overcharge Voltage
Protection
ON
Overcurrent
Protection During ON
Charging
Over Discharging
Voltage Protection
OFF
Overcurrent
Protection During
Discharging
OFF
Short-Circuit
Protection
OFF
COUT
OFF
OFF
ON
ON
ON
Delay
(typ)
1s
12 ms
24 ms
12 ms
400 µs
Comment
Once BATHI occurs for longer than the specified duration (1 s typ), the CHG FET is
turned OFF, and bus communication is not valid, the system will support power to the
load with current flow through the CHG FET parasitic diode. This can cause the cell to
discharge. Once the cell voltage reaches the overcharge release voltage for the
specified duration (8 ms typ) the CHG FET is turned ON and bus communication is valid.
If the cell is being charged with excessive current, the threshold will be based on a
hardware limit measurement of –112 mV typ across the CHG + DSG FET (VM – Vss) for
a duration longer than 12 ms (typ), the CHG FET is turned OFF and bus communication
is not valid. This will prevent further charging of the cell. The setting of the CHG bit in the
control Status register is dependent on the OC bit setting in the Flags Bit Definition
register selection.
The FET bit in the Control between the charger is removed and cell voltage falls below
the threshold for greater than 8 ms (typ). COUT is turned back ON. Once the host MCU
takes corrective action OR if the battery charger is removed AND there is a load
detected for a period of 4 ms (typ), the CHG FET is turned ON bus communication is
valid.
If the cell voltage falls to lower than 2.3 V for a duration of 24 ms (typ), the DSG FET is
turned OFF, and bus communication is not valid. The system requires if the charger is
connected and cell voltage rises above threshold for greater than 4 ms (typ). DOUT is
turned back ON and bus communication is valid.
If the cell is being discharged with excessive current, the threshold will be based on a
hardware limit measurement of 150 mV typ across the DSG + CHG FET ( VM – Vss) for
a duration longer than 12 ms (typ), the DSG FET is turned OFF, and bus communication
is not valid. This prevents further discharging of the cell, and the DSG bit in the Control
Status register will be set. If the drop across the DSG + CHG FET is less than the
threshold OR there is no load detected for a duration of 4 ms (typ), the DSG FET is
turned ON and bus communication is valid.
Detection of cell short circuit is measured at VM input. Shorted cell detection is V_BAT –
0.9 V for greater than 400 µs at VM terminal, and the DSG FET is turned OFF, and bus
communication is not valid. The DSG bit in the control Status register will be set. The
system will turn the DSG FET ON if the voltage at VM is below 150 mV OR no load is
detected.
Gas Gauge Control of Discharge DOUT Pin
Firmware Control of DOUT for Protection
The gas gauge firmware can override the hardware-based protection by forcing DOUT low to turn OFF the
discharge FET. However, the firmware cannot override the hardware protection to force discharge.
The following conditions can enable firmware to force DOUT low:
1. BATLOW—Undervoltage protection using CUV settings. If the cell voltage drops below the firmware setting
the DOUT pin transitions to a low to turn off the discharge FET. The Discharge FET is turned back on once
the cell voltage rises above the set hysteresis.
2. OCD condition—If the average discharge current is greater than the set OCD current, the DOUT pin
transitions low to turn of the Discharge FET. The Discharge FET is turned back on once the average current
decreases below the set level.
3. OTD condition—The DOUT will transition low if the discharge current is flowing and the temperature is above
th set OTD threshold.
16
Submit Documentation Feedback
Product Folder Links: bq28z560-R1
Copyright © 2013, Texas Instruments Incorporated