BQ24266_15 Datasheet, PDF (23/41 Pages) Texas Instruments – bq24266 3A, 30V Standalone Single-Input, Single-Cell Switchmode Li-Ion Battery Charger

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bq24266
SLUSBY5F – JUNE 2014 – REVISED AUGUST 2015
RWARM
=
RLO
RLO ´ RHI´ 0.383
- RLO ´ 0.383 - RHI´ 0.383
(6)
Where RHOT is the NTC resistance at the hot temperature and RCOLD is the NTC resistance at cold
temperature.
The WARM and COOL thresholds are not independently programmable. The COOL and WARM NTC
resistances for a selected resistor divider are calculated using Equation 5 and Equation 6.
V_{BATREG 1 x Charge/}
DISABLE – 140 mV 0.5 x Charge
V_DRV
bq24266
TS COLD
+
TS COOL
+
TS WARM ₊
TS HOT
+
V_DRV
RHI
TS
PACK+
TEMP
RLO
PACK–
Figure 13. TS Circuit
7.4.14 Thermal Regulation and Protection
During the charging process, to prevent overheating in the chip, bq24266 monitors the junction temperature, T_J,
of the die and reduces the input current once T_J reaches the thermal regulation threshold, T_REG. The input
current is reduced to zero when the junction temperature increases about 10°C above T_REG. Once the input
current is reduced to 0, the system current is reduced while the battery supplements the load to supply the
system. When the input current is completely reduced to 0 and T_J>125°C, this is may cause a thermal shutdown
of the bq24266 if the die temperature rises too high. At any state, if T_J exceeds T_SHTDWN, bq24266 stops charging
and disables the buck converter. During thermal shutdown mode, PWM is turned off and all timers are
suspended. The charge cycle resumes when T_J falls below T_SHTDWN by approximately 10°C.
7.4.15 Status Outputs (CHG, PG)
The CHG and PG outputs are used to indicate operating conditions for the bq24266. The PG output indicates
that a valid input source is connected to V_IN. PG is low when (V_BAT + V_SLP) < V_IN < V_OVP. When there is no supply
connected to the input within this range, PG is high impedance. Table 2 illustates the PG behavior under different
conditions.
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