BQ25060_1 Datasheet, PDF (15/24 Pages) Texas Instruments – 1A, Single-Input, Single Cell Li-Ion Battery Charger with 50-mA LDO, and External Power Path Control

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bq25060
SLUSA32 – MAY 2010
Input voltage falls due to
adapter current limit
V_IN
Input current limit is
reduced to prevent
crashing the input
supply
I_LIM
2 V/div
200 mA/div
1 ms/div
Figure 20. bq25060 V_IN-DPM
External NTC Monitoring (TS)
The bq25060 features a flexible, voltage based external battery pack temperature monitoring input. The TS input
connects to the NTC thermistor in the battery pack to monitor battery temperature and prevent dangerous
over-temperature conditions. During charging, the voltage at TS is continuously monitored. If, at any time, the
voltage at TS is outside of the operating range (VCOLD to VHOT), charging is suspended. When the voltage
measured at TS returns to within the operation window, charging is resumed. When charging is suspended due
to a battery pack temperature fault, the CHG output goes to high impedance.
The temperature thresholds are programmed using a resistor divider from LDO to GND with the NTC thermistor
connected to the center tap from TS to GND. See Figure 5 for the circuit example. The value of R1 and R2 are
calculated using the following equations:
R1 = ^{-R2 ´ RHOT ´ (0.125 - 1)}
0.125 ´ (R2 + RHOT)
(3)
R2 =
-RHOT ´ RCOLD ´ (0.125 - 0.250)
RHOT ´ 0.250 ´ (0.125 - 1) + RCOLD´ 0.125 ´ (1 - 0.250)
(4)
RHOT is the expected thermistor resistance at the programmed hot threshold; RCOLD is the expected thermistor
resistance at the programmed cold threshold.
Copyright © 2010, Texas Instruments Incorporated
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