BL1240/1240A Electronic Two –Tone Ringer
Description
BL1240 is a monolithic integrated circuit designed to
TelephoneLine
1
5
Telephone line
Rectifier capacitor
N.C
3
Output frequency control resistor
7
BUZZER
4
8
replace mechanical bell in telephone sets in connection
with an electro-acoustical converter. It can drive directly
a piezoelectricity converter (buzzer) or a dynamic
loudspeaker.
The output current capability of BL1240 is higher than
standard ringer. For driving a dynamic loud-speaker
BL1240 can simply use a decoupling capacitor, thus
eliminating the usual transformer.
No current limitation is provided on the output stage of
BL1240, so a minimum load DC of 50 ohm is advised,
in series with a proper capacitor.
The two tone frequencies generated are switched by an
internal oscillator in a fast sequence and made audible
GND
Sweep Rate Control capacitor
2
6
8pin DIP package
Features
Low current consumption, in order to allow the parallel operation of 4 devices.
Integrated rectifier bridge with zener diodes to protect against overvoltages.
Little external circuitry.
Tone and switching frequencies adjustable by external components.
Integrated voltage and current hysteresis.
Pin connection
Pin
1
2
3
4
5
6
7
8
Symble
LINE
GND
Csw
R
A
OUT
NC
C
r
LINE
Function Description
Telephone line
Ground
Sweep rate control capacitor
Output frequency control resistor
Output frequency
Not connected
Rectifier capacitor
Telephone line
Address： No.810, YiShan Road ShangHai China Tel：86-021-64850700
Fax：86-64852222 Zip.200233
BL1240/1240A Electronic Two –Tone Ringer
BLOCK DIAGRAM
TELEPHONE
LINE
8
IN
RECTIFIER
CAPACITOR
7
N.C.
6
THRESHOLD
CIRCUIT
WITH
HYSTERESIS
BUZZER
5
+
RECTIFIER
BRIDGE
OUTPUT
STAGE
-
IN
SWITCHING
FREQUENCY
GENERATOR
TONE
FREQUENCY
GENERATOR
1
TELEPHONE
LINE
2
GND
3
SWEEP RATE
CONTROL CAPACITOR
4
OUTPUT FREQUENCY
CONTROL RESISTOR
Figure 1 :
Test Circuit
1 uF
2.2 k
8
V
AB
10 uF
Vs
7
1
2
C1
100
nF
5
R
L
3
4
R1
14 k
V
OUT
2 .7 2
*
0
4
1
f
1
*
(1
−
0.04 ln
R
1
=
)
f
1 (
Hz
)
1943
f
2
=
0.725
f
1
f
SWEEP
=
750
C
1 (
nF
)
ABSOLUTE MAXIMUM RATING
( Ta = 25
°C
unless otherwise specified )
Address： No.810, YiShan Road ShangHai China Tel：86-021-64850700
Fax：86-64852222 Zip.200233
BL1240/1240A Electronic Two –Tone Ringer
Parameter
Calling Voltage (f = 50 Hz) Continuous
Calling Voltage (f = 50 Hz) 5s ON/10s OFF
DC Supply Current
Operating Temperature
Storage and Junction Temperature
Symbol
V
AB
(ON)
V
AB
(ON/OFF)
I
DC
Tamb
Tstg
Value
120
200
30
-20 to +70
-65 to +150
Unit
Vrms
Vrms
mA
°C
°C
RECOMMENDED OPERATING CONDITION
( Ta = 25
°C
unless otherwise specified )
Parameter
Symbol
Calling Voltage (f=25Hz) Continuous
VAB(ON)
Min
.
60
Typ.
75
Max
.
90
Unit
Vrms
ELECTRICAL CHARACTERISTICS ( Ta = 25
°C
)
Parameter
DC Power Supply Voltage
Current Consumption without Load
(pins 8-1)
Activation Voltage
Sustaining Voltage
Differential Resistance in OFF
Condition (pins 8-1)
Output Voltage Swing
Short Circuit Current (pins 5-2)
Symbol
V
DC
I
DCO
V
ON
V
OFF
R
D
V
OUT
I
OUT
V
DC
= 20 V,
R
L
= 250
Ω
V
DC
= 9.3
to 2.5 V
12.2
8
Test Conditions
Min.
Typ.
Max.
26
Unit
V
1.5
1.8
13.2
9
mA
V
V
kΩ
6.4
V
DC
- 5
70
V
mA
Output Frequency
f1
V
DC
= 26 V,
R
A
= 14 kΩ,
V3 = 0V
V
DC
= 26 V,
R
A
= 14 kΩ,
V3 = 6V
1.74
2.14
kHz
Output Frequency
f2
f1 / f2
1.22
1.33
1.6
1.43
kHz
Sweep Frequency
f sw
V
DC
= 26 V,
R
A
= 14 kΩ,
Csw = 0.1 uF
7.5
Hz
AC OPERATION
Address： No.810, YiShan Road ShangHai China Tel：86-021-64850700
Fax：86-64852222 Zip.200233
BL1240/1240A Electronic Two –Tone Ringer
Figure 2 :
Typical Application with BUZZER
1 uF
2.2 k
LINE
8
7
5
BUZZER
Z
LOAD
> 1kohm
10 uF
1
2
C1
100
nF
3
4
R1
14 k
Figure 3 :
Typical Application with Loudspeaker (no transformer needed)
1 uF
2.2 k
C1
8
5
LINE
10 uF
7
1
2
C1
100
nF
3
4
RL = 50
Ω
to 1000
R1
14 k
Address： No.810, YiShan Road ShangHai China Tel：86-021-64850700
Fax：86-64852222 Zip.200233
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