BQ24257 Datasheet, PDF (26/45 Pages) Texas Instruments – 2A Single Input I2C, Standalone Switch-Mode Li-Ion Battery Charger with Integrated Current Sense Resistor

bq24257
bq24258
SLUSBG0B – FEBRUARY 2013 – REVISED JULY 2013
www.ti.com
V _BATREG
ICHG
Charge voltage
No charge
Charge current
No charge
4.25V max
4.20V typ
0.5C
Maximum Charge Current: 1C
4.10V max
4.06V typ
0°C
(cold)
10°C
(cool)
Temperature
45°C
(warm)
60°C
(hot)
Figure 22. JEITA Profile for Voltage and Current Regulation Loops
No charge
No charge
Production Test Mode
To aid in end mobile device product manufacturing, the bq24257 includes a Production Test Mode (PTM), where
the device is essentially a DC-DC buck converter. In this mode the input current limit to the charger is disabled
and the output current limit is limited only by the inductor cycle-by-cycle current (e.g. 3.5A). The PTM mode can
be used to test systems with high transient loads such as GSM transmission without the need of a battery being
present.
As a means of safety, the Anyboot algorithm will determine if a battery is not present at the output prior to
enabling the PTM mode. If a battery is present and the software attempts to enter PTM mode, the device will not
enable PTM mode.
Fault Modes
The bq2425x family includes several hardware fault detections. This allows for specific conditions that could
cause a safety concern to be detected. With this feature, the host can be alleviated from monitoring unsafe
charging conditions and also allows for a “fail-safe” if the host is not present. Table 5 summarizes the faults that
are detected and the resulting behavior.
Fault Condition
Input OVP
Input UVLO
Sleep (VIN < VBAT)
TS Fault (Batter Over Temp)
Thermal Shutdown
Timer Fault
No Battery
ISET Short
Input Fault and LDO Low
Table 5. Fault Condition
Charger Behavior
VSYS and ICHG Disabled
VSYS and ICHG Disabled
VSYS and ICHG Disabled
VSYS Active and ICHG Disabled
VSYS and ICHG Disabled
VSYS Active and ICHG Disabled
VSYS Active and ICHG Disabled
VSYS Active and ICHG Disabled
VSYS and ICHG Disabled
Safety Timer Behavior
Suspended
Reset
Suspended
Suspended
Suspended
Reset
Suspended
Suspended
Suspended
Safety Timer
At the beginning of charging process, the bq24257 starts the safety timer. This timer is active during the entire
charging process. If charging has not terminated before the safety timer expires, the IC enters suspend mode
where charging is disabled. The safety timer time is selectable using the I2C interface. A single 256μs pulse is
sent on the STAT and INT outputs and the FAULT/ bits of the status registers are updated in the I2C.
This function prevents continuous charging of a defective battery if the host fails to reset the safety timer. The
safety timer runs at 2x the normal rate under the following conditions: Pre-charge or linear mode (minimum
system voltage mode), during thermal regulation where the charge current is reduced, during TS fault where the
charge current reduced due to temperature rise on the battery, input current limit. The safety timer is suspended
during OVP, TS fault where charge is disabled, thermal shut down, and sleep mode.
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