TEMIC U2407B Datasheet

Simple Controller for Fast Charge Systems

Description

The bipolar IC U2407B is a fast charge battery controller
for drained NiCd/ NiMH batteries. Apart from phase
control, it is identical with U2405B, but has four LED
outputs. The IC enables the designer to create an efficient
and economic charge system. The U2407B incorporates
an intelligent multiple-gradient battery-voltage moni­toring combined with temperature and failure mode

detection. With automatic top-off charging, the
integrated circuit ensures that the charge device stops
regular charging before the critical stage of overcharging
is achieved. It incorporates an additional algorithm for
reactivating fully drained batteries especially after long
time storage. It has four LED driver outputs for different
indications of the charge status.

U2407B

Features

D

Multiple gradient monitoring

D

Temperature window (T

D

Exact currentless measurement

D

Four LED status outputs

D

Linear power control

D

Preferred for externally regulated current sources

D

Preformation algorithm for drained batteries

D

Programmable top-off charge function

6.5 V/10 mA

16

14

1

Switch output

Power - on control

Power supply

= 8 to 26 V

V

S

V

min/Tmax

13

Ref

)

Applications

D
D
D

Package: DIP16/ SO16

12

Oscillator

Control unit

Gradient

2

d

V/dt2 and –dV

160 mV

Ref

Primary switch mode
AC/ DC wall plug adapter
Ultra fast charger (10 minutes)

2

15

Status control

Scan path

Battery

detection

V

Ref

V

Batt

0.1 to 4 V

Temp. control

max

Sensor

T

Charge break

output

3

= 5 V

monitor

10

11

9

95 10648

TELEFUNKEN Semiconductors

Rev . A4, 05-Mar-97

4

5

Figure 1. Block diagram

67

8

1 (16)

U2407B

Input Voltage

8 V to 24 V

Mounted

heatsink

BYW52

Battery

10 mF

on

0.2

10

W

R

T

2

BC237

R

1 k

R

10 k

R

10 k

1

B1

W

B2

W

B3

W

R

1 k

W

BD649

T

1

I

ch

7

C

10

D

1

R

sh

W

2.2 k

10 k

R

R

4

W

100 k

6

W

R

8

W

1 mF

C

R

2.2 k

R

C

1 mF

C
1 mF

5

W

LED1
LED2
LED3

LED4

OP

V

7

Sensor

4

Batt

OP

O

I

V

S

10

2
3

15

4

U2407B

9

7

5

14

220 mF

C

1

GND

1

C

2

0.22 mF

V

Ref

13

R

T3

1.5 k

R

100 k

W

R

270 k

T2

W

O

W

95 10677

T

max

6

Output

16

Osc

12

C

O

8

t

S

p

TM

11

10 nF

Pin Description

Package: DIP16/ SO16

GND

LED2

LED3

OP

OP

T

Sensor

t

p

O

max

1

2

3

4

5

I

6

7

8

Figure 2. Scheme for DC linear regulation

Pin Symbol Function

1 GND Ground

Output

16

15

LED4

2 LED2 Display output “top-off/ trickle

3 LED3 Display output “Fast charge”
4 OP

14

V

S

5 OPIOperational amplifier input
6 T

13

V

Ref

7 Sensor Temperature sensor
8 t

12

Osc

9 V
10 LED1 Display output “failure mode”
11 S
12 Osc Oscillator
13 V
14 V
15 LED4 Display output “top-off charge”
16 Output Trigger output

95 10618

11

10

9

S

TM

LED1

V

Batt

charge”

Operational amplifier output

O

Maximum temperature

max

Charge break output

p

Battery voltage

Batt

Test mode switch (status control)

TM.

Reference output voltage

Ref

Supply voltage

S

2 (16)

TELEFUNKEN Semiconductors

Rev . A3, 05-Mar-97

General Description

The integrated circuit, U2407B, is designed for charging
Nickel-Cadmium (NiCd) and Nickel-Metal-Hydride
(NiMH) batteries. Fast charging results in voltage lobes
when fully charged (figure 3). It supplies two
identifications (i.e., + d
charge operation at the proper time.

As compared to the existing charge concepts where the
charge is terminated * after voltage lobes * according
to – DV and temperature gradient identification, the
U2407B takes into consideration the additional changes
in positive charge curves, according to the second
derivative of the voltage with respect to time (d
The charge identification is the sure method of switching
off the fast charge before overcharging the battery. This
helps to give the battery a long life by hindering any
marked increase in cell pressure and temperature.

Even in critical charge applications, such as a reduced
charge current or with NiMH batteries where weaker

2

V/dt2, and – DV) to end the

2

V/dt2).

U2407B

charge characteristics are present multiple gradient
control results in very efficient switch-off.

An additional temperature control input increases not
only the performances of the charge switching
characteristics but also prevents the general charging of
a battery whose temperature is outside the specified
window.

A specific preformation algorithm is implemented for
reactivating fully drained batteries especially in the case
of batteries that have been stored for a long time.

A constant charge current is necessary for continued
charge-voltage characteristic. This constant current is
generated from an external power supply and can be regu­lated with the help of an internal op-amp regulator
(figure 2). An external current source can also be con­trolled by the switch output Pin 16 (see figure 12).

For further information please refer to the applications.

Battery
voltage

5 V

1.6 V

95 10616

Battery insertion

preformation

I (R

B1)

t1 = 5 min

–DV

)

Fast charge rate I

Figure 3. Charge function diagram, f

Fast charge stop

d

)

dt

2

d

V

,–DV

2

dt

O

= 800 Hz

osc

2

V

2

Top-off charge stop

without

charge control

Top-off

charge rate

1/4 I

O

t2 = 20 min

–DV

Trickle

charge rate

1/256 I

O

t

TELEFUNKEN Semiconductors

Rev . A4, 05-Mar-97

3 (16)

U2407B

Flow Chart Explanation, f

= 800 Hz

osc

(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 V
5 minutes the d
–DV monitoring is activated. In case the detected V
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

(see figure 2).

R

B3

Preformation Procedure

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

. The fast charge starts only after the V

R

B1

than 1.6 V. During the first 10 minutes the green LED2 is
blinking. If after 10 minutes, V
reached the reference level, the indication changes to red
blinking LED1. The charge will continue with
preformation rate I (R
reference level, the fast charge rate current, I
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 d
In this actual charge stage, all stop-charge criteria are
active.

is higher than 1.6 V. For the first

Batt

2

V/dt2-gradient recognition is suppressed,

is higher

Batt

voltage has not

Batt

). In case V

B1

2

V/dt2 monitoring will be active.

increases to 1.6 V

Batt

o

Batt

, is

Top-Off Charge Stage

By charge disconnection through the +d2V/dt
device switches automatically to a defined protective
top-off charge with a pulse rate of 1/4 I

= 5.12 s, period, T = 20.48 s).

t

p

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.

2

mode, the

(pulse time,

O

Trickle Charge Stage

When top-off charge is terminated, the device switches
automatically to trickle charge with 1/256 I

(tp = 5.12 s,

O

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.

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, R

, to a maximum value of 25 mA. Series resistance

rent, I

S

is recommended to suppress the noise signal, even below
26 V limitation. It is calculated as follows.

1min

R

1max

v

25 mA

V

min

–8V

I

tot

–26 V

V

max

w

R

where
I

= IS + I

tot

V

max, Vmin

I

= Current consumption (IC) without load

S

I

= Current through resistance, R

RB1

+ I

RB1

1

= Rectified voltage

I1 = Trigger current at Pin 1

, regulates the supply cur-

1

B1

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

2

voltage curve will typically rise. As soon as the +d

V/dt
stop-charging criteria are met, the device will stop the fast
charge activities.

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2

TELEFUNKEN Semiconductors

Rev . A3, 05-Mar-97

U2407B

*) 70 mV > V

LED1 blinking

Fast charge

begins

Batt

> 5V

Start

no

Reset

Temp. range

ok ?

Power on reset

LED1,2,3,4 off

yes

Batt. inserted

yes

*)

Preformation

current I

RB1

LED3 blinking

yes

no

V

Temp. range

Charge stop

LED1 blinking

> 1.6 V

Batt

yes

no

ok ?

yes

no

tch > 10 min

V

4 V

Batt

yes

–dV

switch off

no

no yes

Batt. inserted

*)

no

yes

Charge time

t

–dV and d2V/dt

monitoring activated

no

LED1 blinking

> 5 min ?

1

Batt temp

range?

yes yes

no

2

yes

–dV

disconnect

LED2 on

Trickle charge

1/256 I

O

Batt. inserted

*)

yes

no

LED1 blinking

Batt. inserted

*)

no

no

2

d2V/dt

disconnect ?

LED2 on
LED4 on

Top off charge

1/4 I

O

t2 > 20 min

LED3 off

no

no

95 10671

TELEFUNKEN Semiconductors

Rev . A4, 05-Mar-97

Figure 4. Flow chart

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