Flow Chart Explanation, fosc = 800 Hz
(Figures 2, 3 and 4)
Battery pack insertion disables the voltage lock at battery
detection input Pin 10. All functions in the integrated
circuit are reset. For further description, DIP-pinning is
taken into consideration.
Battery Insertion and –DV
After battery insertion fast charge Io begins when the
input voltage VBatt is higher than 1.6 V. For the first
5 minutes the d2V/dt2-gradient recognition is suppressed,
–DV monitoring is activated. In case the detected VBatt
voltage is less then 1.6 V, the special preformation
procedure will be activated. The reference level with
respect to the cell voltage can be adjusted by the resistor
RB3 (see figure 2).
Before fast charge of fully drained or long time stored
batteries begin, a reactivation is necessary. The
preformation current is dependent on pull-up resistor
RB1. The fast charge starts only after the VBatt is higher
than 1.6 V level. During the first 10 minutes the green
LED2 is blinking. If, after 10 minutes, VBatt voltage has
not reached the reference level, the indication changes to
red blinking LED1. The charge will continue with
preformation rate I (RB1). In case VBatt increases to 1.6 V
reference level, the fast charge rate current, Io, is
switched-on and the green LED2 is blinking.
–DV Cut-Off (Monitoring)
When the signal at Pin 10 of the DA converter is 12 mV
below the actual value, the comparator identifies it as a
voltage drop of –DV. The validity of –DV cut-off is
considered only if the actual value is below 12 mV for
three consecutive cycles of measurement.
If there is no charge stop within the first 5 minutes after
battery insertion, then d2V/dt2 monitoring will be active.
In this actual charge stage, all stop-charge criteria are
When close to the battery’s capacity limit, the battery
voltage curve will typically rise. As long as the +d2V/dt2
stop-charging criteria are met, the device will stop the fast
Top-Off Charge Stage
By charge disconnection through the + d2V/dt2 mode, the
device switches automatically to a defined protective
top-off charge with a pulse rate of 1/4 IO (pulse time,
tp = 5.12 s, period, T = 20.48 s).
The top-off charge time is specified for a time of
20 minutes @ 800 Hz.
Trickle Charge Stage
When top-off charge is terminated, the device switches
automatically to trickle charge with 1/256 IO (tp = 5.12 s,
period = 1310.72 s). The trickle continues until the
battery pack is removed.
Power Supply, Figure 2
The charge controller allows the direct power supply of
8 to 26 V at Pin 15. Internal regulation limits higher input
voltages. Series resistance, R1, regulates the supply
current, IS, to a maximum value of 25 mA. Series
resistance is recommended to suppress the noise signal,
even below 26 V limitation. It is calculated as follows.
Vmin– 8 V
Itot = IS + IRB1 + I1
Vmax, Vmin = Rectified voltage
IS = Current consumption (IC) without load
IRB1 = Current through resistance, RB1
I1 = Trigger current at Pin 1
Rev. A2, 14-Nov-96