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U2407B

Simple Controller for Fast Charge Systems

Temic Semiconductors 

U2407B

Flow Chart Explanation, fosc = 800 Hz

(Figures 2, 3 and 4)

Battery pack insertion disables the voltage lock at battery

detection input Pin 9. All functions in the integrated

circuit are reset. For further description, DIP-pinning is

taken into consideration.

Battery Insertion and –DV

Monitoring

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).

Preformation Procedure

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.

During top-off mode the LED4 is in ON mode.

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.

During trickle mode the LED2 output is in on mode,

LED4 is in OFF-mode.

Before fast charge of fully drained or long-time stored

batteries begins, a reactivation of it 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. 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 9 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.

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.

Basic Description

Power Supply, Figure 2

The charge controller allows the direct power supply of

8 to 26 V at Pin 14. Internal regulation limits higher input

voltages. Series resistance, R1, regulates the supply cur-

rent, 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.

w R1min

Vmax–26 V

25 mA

v R1max

Vmin– 8 V

Itot

where

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

When close to the battery’s capacity limit, the battery

voltage curve will typically rise. As soon as the +d2V/dt2

stop-charging criteria are met, the device will stop the fast

charge activities.

4 (16)

TELEFUNKEN Semiconductors

Rev. A3, 05-Mar-97

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