U2405B
Flow Chart Explanation, f
osc
= 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.
Top-Off Charge Stage
By charge disconnection through the + d
2
V/dt
2
mode, the
device switches automatically to a defined protective
top-off charge with a pulse rate of 1/4 I
O
(pulse time,
t
p
= 5.12 s, period, T = 20.48 s).
The top-off charge time is specified for a time of
20 minutes @ 800 Hz.
Battery Insertion and –
D
V
Monitoring
After battery insertion fast charge I
o
begins when the
input voltage V
Batt
is higher than 1.6 V. For the first
5 minutes the d
2
V/dt
2
-gradient recognition is suppressed,
–
D
V monitoring is activated. In case the detected V
Batt
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
R
B3
(see figure 2).
Trickle Charge Stage
When top-off charge is terminated, the device switches
automatically to trickle charge with 1/256 I
O
(t
p
= 5.12 s,
period = 1310.72 s). The trickle continues until the
battery pack is removed.
Preformation Procedure
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
R
B1
. The fast charge starts only after the V
Batt
is higher
than 1.6 V level. During the first 10 minutes the green
LED2 is blinking. If, after 10 minutes, V
Batt
voltage has
not reached the reference level, the indication changes to
red blinking LED1. The charge will continue with
preformation rate I (R
B1
). In case V
Batt
increases to 1.6 V
reference level, the fast charge rate current, I
o
, is
switched-on and the green LED2 is blinking.
Basic Description
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, R
1
, regulates the supply
current, I
S
, 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.
R
1min
R
1max
w
V25–26 V
mA
max
–
D
V 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 –
D
V. The validity of –
D
V cut-off is
considered only if the actual value is below 12 mV for
three consecutive cycles of measurement.
v
V
min
– 8 V
I
tot
where
I
tot
= I
S
+ I
RB1
+ I
1
V
max,
V
min
= Rectified voltage
I
S
= Current consumption (IC) without load
I
RB1
= Current through resistance, R
B1
I
1
= Trigger current at Pin 1
d
2
V/dt
2
-Gradient
If there is no charge stop within the first 5 minutes after
battery insertion, then d
2
V/dt
2
monitoring will be active.
In this actual charge stage, all stop-charge criteria are
active.
When close to the battery’s capacity limit, the battery
voltage curve will typically rise. As long as the +d
2
V/dt
2
stop-charging criteria are met, the device will stop the fast
charge activities.
TELEFUNKEN Semiconductors
Rev. A2, 14-Nov-96
5 (17)
TEMIC [ TEMIC SEMICONDUCTORS ]
