BQ24085 Datasheet, PDF (16/34 Pages) Texas Instruments – 750 mA SINGLE-CHIP Li-Ion/Li-Pol CHARGE MANAGEMENT IC WITH THERMAL REGULATION

bq24085, bq24086
bq24087, bq24088
SLUS784B – DECEMBER 2007 – REVISED MAY 2008 .................................................................................................................................................... www.ti.com
V_IN
V_C(TS2)
0.6 x V_IN
V_C(TS1)
0.3 x V_IN
Charge Suspend
Normal Temperature
Charge Range
Charge Suspend
Figure 15. Battery Temperature Qualification With NTC Thermistor
The external resistors R_T1 and R_T2 (see Figure 13) enable selecting a temperature window. If R_TC and R_TH are
the thermistor impedances for the Cold and Hot thresholds the values for R_T1 and R_T2 can be calculated as
follows, for a NTC (negative temperature coefficient) thermistor. Solve for R_T2 first and substitute into R_T1
equation.
R_T2
+
2.5 R_TCR_TH
R_TC * 3.5 R_TH
(1)
R_T1
+
3
7 R_THR_T2
ƪ_{RTH ) RT2}ƫ
(2)
Applying a fixed voltage, 1/2 Vin (50% resistor divider from Vin to ground), to the TS pin to disable the
temperature sensing feature.
INPUT OVERVOLTAGE DETECTION, POWER GOOD STATUS OUTPUT
The input power detection status for pin IN is shown at the open collector output pin PG.
Table 2. Input Power Detection Status
INPUT POWER DETECTION (IN)
NOT DETECTED
DETECTED, NO OVERVOLTAGE
DETECTED, OVERVOLTAGE
PG STATE
High impedance
LO
High impedance
The bq24085/6/7/8 detects an input overvoltage when V_(IN) > V_(OVP). When an overvoltage protection is detected
the charger function is turned off and the bq24085/6/7/8 is set to standby mode of operation. The OVP detection
is not latched, and the IC returns to normal operation when the fault condition is removed.
CHARGE STATUS OUTPUTS
The open-collector STAT1 and STAT2 outputs indicate various charger operations as shown in Table 3. These
status pins can be used to drive LEDs or communicate to the host processor. Note that OFF indicates the
open-collector transistor is turned off. When termination is disabled (TMR pin floating, or TE = Hi for bq24087)
the Done state is not available; the status LEDs indicate fast charge if V_(BAT) > V_(LOWV) and precharge if V_(BAT) <
V_(LOWV). The available output current is a function of the OUT pin voltage, See Figure 20.
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