U2402B Datasheet, PDF (5/17 Pages) TEMIC Semiconductors – Fast Charge Controller for NiCd/NiMH Batteries

U2402B
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.
Battery Insertion and –dV Monitoring
The charging procedure will be carried out if battery
insertion is recognised. If the polarity of the inserted
battery is not according to the specification, the fast
charge rate will stop immediately. After the polarity test,
if positive, the defined fast charge rate, I_O, begins for the
first 5 minutes according to –dV monitoring. After
5 minutes of charging, the first identification control is
executed.
If the inserted battery has a signal across its terminal of
less than 0.1 V, then the charging procedure is interrupted.
This means that the battery is defective i.e., it is not a
rechargeable battery – “shorted batteries ignored”.
Voltage and temperature measurements across the battery
are carried out during charge break interval (see figure 6),
i.e., currentless or idle measurements.
If the inserted battery is fully charged, the –dV control
will signal a charge stop after six measurements
(approximately 110 seconds). All the above mentioned
functions are recognised during the first 5 minutes
according to –dV method. During this time, +d²V/dt²
remains inactive. In this way the battery is protected from
unnecessary damage.
d²V/dt²-Gradient
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
active.
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
charge activities.
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 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.
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.
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, R₁, 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:
w R_1min
V_max–26 V
25 mA
v R_1max
V_min– 8 V
I_tot
where
I_tot = I_S + I_RB1 + I₁
V_max, V_min = Rectified voltage
I_S = Current consumption (IC) without load
I_RB1 = Current through resistance, R_B1
I₁ = Trigger current at Pin 1
TELEFUNKEN Semiconductors
Rev. A3, 14-Nov-96
5 (17)