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| BQ2057DGKR Datasheet, PDF (12/24 Pages) Texas Instruments – ADVANCED LINEAR CHARGE MANAGEMENT IC FOR SINGLE AND TWO CELL LITHIUM-POLYMER | |||
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bq2057, bq2057C
bq2057T, bq2057W
SLUS025F â MAY 2001 â REVISED JULY 2002
DC+
RSNS
DCâ
bq2057
SNS
COMP
BAT
CC
VCC
VSS
TS
STAT
APPLICATION INFORMATION
DC+
RB1
RB2
BAT+
BATâ
DCâ
bq2057
SNS
COMP
BAT
CC
VCC
VSS
TS
STAT
RB1
RB2
RSNS
BAT+
BATâ
Figure 7. Optional Voltage Divider for
Nonstandard Regulation Voltage,
(High-Side Current Sensing)
Figure 8. Optional Voltage Divider for
Nonstandard Regulation Voltage,
(Low-Side Current Sensing)
charge termination and recharge
The bq2057 monitors the charging current during the voltage-regulation phase. The bq2057 declares a done
condition and terminates charge when the current tapers off to the charge termination threshold, I(TERM). A new
charge cycle begins when the battery voltage falls below the V(RCH) threshold.
battery temperature monitoring
The bq2057 continuously monitors temperature by measuring the voltage between the TS and VSS pins. A
negative- or a positive-temperature coefficient thermistor (NTC, PTC) and an external voltage divider typically
develop this voltage. (See Figure 9.) The bq2057 compares this voltage against its internal V(TS1) and V(TS2)
thresholds to determine if charging is allowed. (See Figure 10.) The temperature sensing circuit is immune to
any fluctuation in VCC, since both the external voltage divider and the internal thresholds (V(TS1) and V(TS2))
are referenced to VCC.
The resistor values of R(T1) and R(T2) are calculated by the following equations:
For NTC Thermistors
Ç Ç 5
RT1 + 3
RTH RTC
RTC * RTH
(3)
ƪ ƫ RT2 +
5 RTH RTC
Ç2 RTCÇâÇ7 RTHÇ
(4)
12
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