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| BQ2057CTSTRG4 Datasheet, PDF (18/30 Pages) Texas Instruments – ADVANCED LINEAR CHARGE MANAGEMENT IC FOR SINGLE-AND TWO-CELL LITHIUM-ION AND LITHIUM-POLYMER | |||
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bq2057, bq2057C
bq2057T, bq2057W
SLUS025F â MAY 2001 â REVISED JULY 2002
APPLICATION INFORMATION
automatic charge-rate compensation (continued)
AutoComp setup requires the following information:
D Total impedance of battery pack (Z(PACK))
D Maximum charging current (I(REG))
The voltage drop across the internal impedance of battery pack, V(Z), can then be calculated using the following
equation:
V(Z) = Z(PACK) Ã I(REG)
(13)
The required compensation is then calculated using the following equations:
V(COMP)
+
V(Z)
G(COMP)
(14)
Ç Ç V(PACK) + VO(REG) ) G(COMP) V(COMP
Where V(COMP) is the voltage on COMP pin. This voltage is referenced to VCC in high-side current sensing
configuration and to VSS for low-side sensing. V(PACK) is the voltage across the battery pack.
The values of R(COMP1) and R(COMP2) can be calculated using the following equation:
V(COMP)
V(SNS)
+
RCOMP2
RCOMP1 ) RCOMP2
(15)
DC+
RCOMP2
RSNS
DCâ
RCOMP1
bq2057
SNS
COMP
BAT
VCC
CC
VSS
TS
STAT
BAT+
DC+
DCâ
bq2057
SNS
COMP
BAT
VCC
CC
VSS
TS
STAT
RCOMP2
RSNS
BAT+
RCOMP1
High-Side Current Sensing
Figure 13. AutoComp Circuits
Low-Side Current Sensing
BATâ
18
www.ti.com
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