Preliminary
CBC910
Battery charging and backup power for 2.5 to 5.5 volt operation is selected by changing the value of R2. To
determine the battery backup switchover point, set the value of R1 to 200kΩ and choose the value of R2
according to Figure 6. For example, to set a 3.0V trip point: If R1=200 kΩ then R2 = R1 x 0.72 = 144kΩ.
Battery Switchover Threshold Voltage vs. R2/R1
Ratio
6
5
4
3
2
1
0
Trip point
0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9
1
1.1
R2/R1 Ratio
Figure 6: MODE 2 Resistor Selection Graph
To determine the battery backup switchover hysteresis for Mode 2 operation, use Figure 7.
Hysteresis in Battery Switchover Threshold
Voltage vs. R2/R1 Ratio
0.09
0.08
0.07
0.06
0.05
Hysteresis
0.04
0.03
0.02
0.01
0
0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9
1
1.1
R2/R1 Ratio
Figure 7: Mode 2 Hysteresis as a Function of R2/R1
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DS-72-11 Rev 5
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