ICS1708 Datasheet, PDF (12/16 Pages) List of Unclassifed Manufacturers – QuickSaver Charge Control IC for Nickel-Cadmium and Nickel-Metal Hydride Batteries

ICS1708
Timing Diagram
Figure A:
+5V
CHG
pin 1
FCHG
REST
DATA
ACQUISITION
CYCLE
Applications Information
To ensure proper operation of the ICS1708, external components must be properly selected. The external current source used must meet
several important criteria to ensure adequate performance of the charging system. The charging current source amplitude should be fairly
constant
VIN and OPREF Divider Resistors
Figure 9 shows a typical application using the ICS1708. R1 through R3 must be selected properly to ensure that battery detection and
voltage termination methods operate properly. R1 and R2 are selected to scale the battery voltage down to the voltage of one cell. The
following table shows some typical values.
Cells
R1
R2
1
20k
*
2
20k
20k*
3
39k
20k
4
62k
20k
5
82k
20k
6
100k
20k
7
120k
20k
8
150k
20k
9
160k
20k
10
180k
20k
11
200k
20k
12
220k
20k
13 & Above
R1=R2 x (# cells - 1)
* Use 5.1V Zener as required depending on input voltage
If the current source is a switch mode type, normal ripple current does not effect the ICS1708. However, the effects of line frequency ripple
may interfere with proper performance. R3, per Figure 9, can be used to set the open circuit (no battery) reference voltage on the OPREF
pin. The function of this pin is discussed in the Open Circuit Reference section.
V_OPREF
R3
1.68 V
43k
1.78 V
47k
1.88 V
51k
1.99 V
56k
2.11 V
62k
See Figure 8 for an alternate resistor divider approach at the OPREF pin for tight tolerance applications.
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