ICS1708 Datasheet, PDF (8/16 Pages) List of Unclassifed Manufacturers – QuickSaver Charge Control IC for Nickel-Cadmium and Nickel-Metal Hydride Batteries

ICS1708
As an example, suppose that a current source has an open circuit voltage of 12V as shown in Figure 8.
+5V
R3 = 2.21k, 1%
OPREF = 1.89V
R4 = 1.3k, 1%
+
6 cells
(9.6 V)
-
current source on (no battery)
(open circuit voltage = 12V)
R1 = 100k
VIN
= _{^12..6000VV
(battery present)
(no battery)
R2 = 20k
Alternate resistor divider at the OPREF Resistor divider at the VIN
pin for tight tolerance applications
pin
Figure 8: Open Circuit Reference Example
The maximum battery voltage of a nearly full six-cell pack with current applied is determined to be 9.6V. The voltage at OPREF should
then be set at a point between 1.6V (9.6V/6 cells=1.6V) and 2V (12V/6=2V). This can be accomplished with a pull-down resistor. Refer to
the VIN and OPREF resistor tables in the Applications Information section. From the VIN table, the divider resistors are 100kΩ and
20kΩ for R1 and R2. From the OPREF table, the pull-down resistor is 47KΩ for R3. If R3 is 47KΩ, the voltage at OPREF is typically
1.78V since the internal pull-up at the OPREF pin is 85kΩ. Figure 8 show an alternate approach for setting the voltage on OPREF for tight
tolerance applications.
Power: VDD pin 8
The power supply for the device must be connected to the VDD pin. The voltage is +5 VDC nominal, series regulated for proper noise
rejection. A 100mA or higher current rating supplies the controllers maximum of 11mA average demand that includes brief 50mA peaks.
Peripheral circuits current requirements are added to these requirements. See Pin Descriptions for additional information.
Grounding: VSS pin 6
This pin is connected directly to a solid (low impedance) ground that connects at or close to battery minus. See the section Pin Descriptions
and Applications Information (PC Board Design Considerations) for additional information.
Charge Rate Selection
The voltage set on CMN pin 3 prior to the start of fast charge sets one of three fast charge rates shown in Table 2.
Table 2: Charge Rate List
Selected Charge Rate
4C (15 min)
1C (60 min)
C/2.5 (150 min)
Topping Charge Pulse
Rate
one every 41 sec
one every 11 sec
one every 5 sec
Maintenance Charge
Pulse Rate
one every 161 sec
one every 41 sec
one every 17 sec
Fast Charge Timer
Duration (after power-
up or battery insertion)
21 min
75 min
212 min
See the section on Controller Operation for additional information on the topping charge and maintenance charge. See the section on Charge Termination
Methods for additional information on the charge timer.
8