ICS1700A Datasheet, PDF (15/24 Pages) List of Unclassifed Manufacturers – QuickSaver Charge Controller for Nickel-Cadmium and Nickel-Metal Hydride Batteries

ICS1700A
Applications Information
To ensure proper operation of the ICS1700A, external components
must be properly selected. The external current source used must
meet several important criteria to ensure optimal performance of
the charging system.
VIN Divider Resistors
Figure 12 shows a typical application using the ICS1700A. R1 and
R2 must be carefully selected 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. Additional
information is available in the Voltage Input section
Cells
1
2
3
4
5
6
7
8
R1
Short
2.0k
2.0k
3.0k
12k
10k
12k
9.1k
R2
Open
2.0k
1.0k
1.0k
3.0k
2.0k
2.0k
1.3k
PC Board Design Considerations
It is very important that care be taken to minimize noise coupling
and ground bounce. In addition, wires and connectors can add
significant resistance and inductance to the charge and discharge
circuits.
When designing the printed circuit board, make sure ground
and power traces are wide and bypass capacitors are used
right at the controller. Use separate grounds for the signal,
charge and discharge circuits. Separate ground planes on the
component side of the PC board are recommended. Be sure
to connect these grounds together at the negative lead of the
battery only. For the discharge circuit, keep the physical
separation between power and return (ground) to a minimum
to minimize field radiation effects. This precaution is also
applicable to the constant current source, particularly if it is
a switch mode type. Keep the ICS1700A and the constant
current source control circuits outside the power and return
loop described above. These precautions will prevent high
circulating currents and coupled noise from disturbing
normal operation.
Voltage Slope Termination
In general, the voltage slope termination method works best for
equipment where the battery is fast charged with the equipment off
or the battery is removed from the equipment for fast charge. The
voltage slope termination method works best with a constant
current flow into the battery during fast charge. If equipment draws
a known constant current while the battery is charging, this current
should be added to the fast charge cur-rent. Equipment that
randomly or periodically requires current from the battery during
fast charge needs evaluation to ensure it does not interfere with the
proper operation of the voltage slope termination method.
Charging sources that produce decreasing current as fast charge
progresses may cause a voltage inflection that may result in
termination before full charge. For example, if the charge current is
supplied through a resistor or if the charging source is a constant
current type that has insufficient input voltage, the current will
decrease and may cause a termination before full charge. Other
current source characteristics that can cause a voltage inflection
that is characteristic of a fully charged battery are inadequate ripple
and noise attenuation capability or charge current decreasing due to
thermal drift. Charging sources that have any of the above
characteristics need evaluation to access their suitability for the
application.
The controller soft start stage, built-in noise filtering, and fast
charge timer operate optimally when the constant cur-rent source
charges the battery at the rate selected. If the actual charge current
is significantly less than the rate selected, the conditioning effect of
the soft start stage and the controller noise immunity are lessened.
Also, the fast charge timer may cause termination based on time
duration rather than by the battery reaching full charge due to
inadequate charge current.
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