Datasheet
SLUS025F − MAY 2001 − REVISED JULY 2002
18
www.ti.com
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)
× I
(REG)
The required compensation is then calculated using the following equations:
V
(COMP)
+
V
(Z)
G
(COMP)
V
(PACK)
+ V
O(REG)
)
ǒ
G
(COMP)
V
(COMP
Ǔ
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)
+
R
COMP2
R
COMP1
) R
COMP2
SNS
BAT
VCC
TS
COMP
CC
VSS
STAT
bq2057
DC+
DC−
BAT+
SNS
BAT
VCC
TS
COMP
CC
VSS
STAT
bq2057
DC+
DC−
BAT+
BAT−
High-Side Current Sensing Low-Side Current Sensing
R
COMP2
R
SNS
R
COMP1
R
COMP1
R
COMP2
R
SNS
Figure 13. AutoComp Circuits
(13)
(14)
(15)