UTC L6726 Universal speech circuit Datasheet

UNISONIC TECHNOLOGIES CO., LTD
L6726
LINEAR INTEGRATED CIRCUIT
UNIVERSAL SPEECH
CIRCUIT
„
DESCRIPTION
The UTC L6726 is a mask-programmable, monolithic
integrated speech circuits for using in electronic telephones.
It is designed for using with a low impedance microphone.
Transmitting and receiving gain are regulated with line length.
Different regulation for various current feeds can be set by
external resistors. Typical current feeds as 48V 2·200Ω, 48V,
2·400Ω, and 36V, 2·500Ω, can be handled. Application
dependent parameters such as line balance, side tone level,
amplification and frequency response are set by external
components. Parameters are set independently which means
easy adaptation for various market needs.
The UTC L6726 is developed for using with CMOS-type dialer
ICs. A separate DTMF input is switched when the circuit is
muted, and an adjustable DC supply is provided for feeding an
external CMOS device.
„
*Pb-free plating product number: L6726L
FEATURES
*Minimum number of inexpensive external components, 5
capacitors and 11 resistors.
*Mute function for operation with DTMF-generator.
*Transmit and receive gain regulation for automatic loop loss
compensation.
*Extended current and voltage range 5~130mA, down to 2V.
*Differential microphone input for good balance to ground.
*Balanced receiver output stage.
*Short start-up time.
*Stabilized DC-supply for low current CMOS dialers and/or
electret microphones.
*DTMF-input controlled by mute.
„
ORDERING INFORMATION
Ordering Number
Normal
Lead Free
L6726-D18-T
L6726L-D18-T
L6726-S18-R
L6726L-S18-R
L6726-S18-T
L6726L-S18-T
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Package
Packing
DIP-18
SOP-18
SOP-18
Tube
Tape Reel
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L6726
LINEAR INTEGRATED CIRCUIT
PIN CONFIGURATION
„
+L
1
18
RE 2
TO
2
17
RE 1
TI
3
16
DR
+C
4
15
RI
Mute
5
14
-L
GR
6
13
MI 2
DCS
7
12
MI 1
DCO
8
11
MO
DCC
9
10
DI
PIN DESCRIPTIONS
„
Pin
No.
Pin
Name
1
+L
2
TO
3
TI
4
+C
5
Mute
6
7
8
9
10
11
12
13
14
15
16
17
18
GR
DCS
DCO
DCC
DI
MO
MI 1
MI 2
-L
RI
DR
RE 1
RE 2
Description
Output of the DC-regulator and transmit amplifier. This pin is connected to the line through a polarity
guard and diode bridge.
Output of the transmit amplifier. This pin is connected through a resistor of 47 to 100Ω to -L, which
sets the DC-resistance of the circuit. The output has a low AC output impedance and the signal is
used to drive a side tone balancing network.
Input of transmit amplifier. Input impedance 17kΩ±20%
The positive power supply terminal for most of the circuitry inside the UTC L6726 (about 1mA current
consumption).The +C-PIN shall be connected to a decoupling capacitor of 47µF to 150µF
When low, speech circuit is muted and the DTMF input is enabled. Maximum voltage (at mute) is
0.3V,current sink requirement of external driver is 50µA
Control input for the gain regulation circuitry.
The sense input to the DC-supply.
The output from the DC-supply.
The control output from the DC-supply
The input for the DTMF-signal. Input impedance is 25kΩ±20%
Output of the microphone amplifier or DTMF-amplifier
Input to the microphone amplifier. Input impedance 1.7kΩ±20%
The negative power terminal, connected to the line though a polarity guard diode bridge
Input of receiver amplifier. Input impedance is approximately 38kΩ±20%
The control input for the receiver amplifier driving capability.
Receiver amplifier outputs. Output impedance is approximately 3Ω.
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„
LINEAR INTEGRATED CIRCUIT
ABSOLUTE MAXIMUM RATINGS
PARAMETER
SYMBOL
RATINGS
UNIT
Line Voltage, tp =2s
VL
0~22
V
Line Current, Continuous
IL
0~130
mA
Ambient Operating Temperature
TOPR
-40~+70
°C
Storage Temperature
TSTG
-55~+125
°C
Note: Absolute maximum ratings are those values beyond which the device could be permanently damaged.
Absolute maximum ratings are stress ratings only and functional device operation is not implied.
„
ELECTRICAL CHARACTERISTICS (Ta=25℃ unless otherwise specified)
PARAMETER
FIG.
Line Voltage
1
Transmitting Gain, Note 1
1
Transmitting Range Of Regulation
Transmitting Frequency Response
1
1
Receiving Gain, Note 1
1
Receiving Range Of Regulation
Receiving frequency response
Microphone Input Impedance
Pin12,13
Transmitter Input Impedance Pin 3
1
1
TEST CONDITIONS
IL=15mA
IL=100mA
20·10log(V2/V3), 1kHz
RL=0Ω
RL=400Ω
RL=900Ω~2.2kΩ
1kHz, RL=0 ~ 900 Ω
200Hz ~ 3.4kHz
20·10log (V4/V1), 1kHz
RL=0Ω
RL=400Ω
RL=900Ω~2.2kΩ
1kHz, RL=0 ~ 900 Ω
200Hz ~ 3.4kHz
1
1kHz, note 3
1
Transmitter Dynamic Output
1
Transmitter Max Output
1
Receiver Output Impedance
1
Receiver Dynamic Output (Note 2)
1
Receiver Max Output
2
Transmitter Output Noise
1
Receiver Output Noise
1
1kHz
200Hz~3.4kHz
≤2% distortion, IL=20~100mA
200 Hz~3.4kHz
IL=0-100mA,V3=0.1V
1kHz, note 3
200Hz~3.4kHz
≤2% distortion, IL=20~100mA
Measured with line rectifier
200 Hz~3.4kHz, IL=0~100mA, V1=0~50V
Psof-weighting, Rel1 Vrms, RL=0
A-weighting, Rel 1Vrms, with cable
0~5km, φ=0.5mm, 0~3km, φ=0.3mm
Mute Input Voltage at Mute
(Active Low)
1
DC-Supply Voltage
1
TYP
3.7
13
MAX UNIT
4.1
V
15
41
43.5
46
43
45.5
48
45
47.5
50
dB
dB
dB
3
-1
5
7
1
dB
dB
-18.5
-16
-13.5
-16.5
-14
-11.5
-14.5
-12
-9.5
dB
dB
dB
3
-1
5
7
1
dB
dB
1.7(//2.7)
kΩ
17
kΩ
1.5
Vp
3
Vp
3(+310)
Ω
0.5
Vp
0.9
Vp
-75
dBpsof
-85
dBA
0.3
IL=10~100mA, IDC=0mA
IL=10~100mA, IDC=2mA
DC-Supply Current, Pin8
1
Dc-Output Pin8 Input Leakage
3 VDC=2.35V
Current (No Supply)
DTMF Transmitting Gain
1 VM=0.3V
Notes: 1. Adjustable to both higher and lower values with external components.
2. The dynamic output can be doubled, see applications information.
3. External resistor in the test set up.
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MIN
3.3
11
2.35
2.2
V
2
mA
0.1
24.5
V
26.5
µA
28.5
dB
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LINEAR INTEGRATED CIRCUIT
FUNCTIONAL DIAGRAM
1
DTMF
input
UTC L6726
10
17
AD
AR
AT
12
Telephone
Line
18
AM
13
DC
8 9 7
5
11
3
2
15
16 6
14
4
DC output for external
3
CMOS device
1
Mute
(active low)
5
2
4
1.Impedance to line and radio interference suppression.
2.Transmit gain and frequency response network.
3.Receive gain and frequency response network.
4.Side tone balance network.
5.DC-supply components.
MUTE
RL=0~4KΩ
0 Ω when artificail line is used
5H+5H
RLoad
=400Ω+400Ω
+
E=48.5V
C1
1μF
V2
+
VM
ARTIFICAIAL
LINE
IL
DTMF
600Ω
VL
IDC
+LINE
VDC
V3
UTC 6726
with external
component
see fig 3
REC
V1
ZMIC=350 Ω
MIC
V4
ZRec=350 Ω
-LINE
C1= 1μF when artificial line is used
470μF when not used
Figure 1. Test setup without rectifier bridge
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LINEAR INTEGRATED CIRCUIT
FUNCTIONAL DIAGRAM(Cont.)
+Line
1
DTMF
input
C8
10
220nF
DC
8 9 7
CMOS device
1
8
AM
13
DC supply OUT
5
Sense input
Control output
R4
18k
11
3
C3
100nF
MUTE
R5
22k
+
47μF
R14
310Ω
AR
AT
12
MIC R16
350Ω 27k
1
7
UTC 6726
AD
R6
75 Ω
C7
15 14 6
2
R7
910 Ω
C4
47nF
R11
560Ω
3kΩ
R8
R9
11k
Note : * Not used in test setup
R13
C5 11k
REC
350 Ω
14 4
R10
82k
910 Ω R3
R1 *
R15 R2 *
10 Ω
47μF
+
C1
C2
15nF
-Line
100nF
Figure 3. Circuit with external components for test setup.
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„
LINEAR INTEGRATED CIRCUIT
FUNCTIONAL DESCRIPTION
The gain of the transmitting and receiving amplifiers are continuously and euqually changed with the line length.
The starting point for the gain regulation is externally set .The gain regulation can be cut-off externally, see table
under gain regulation below.
The outputs of the transmitting and receiving amplifiers have internals limitations of the output amplitudes.
The circuit includes a temperature independent voltage reference used for regulation of the DC line voltage and for
the transmitting and receiving gain regulation. The DC voltage is very fast settled to its final value with a minimum of
overshoot.
The circuit uses a minimum of external components. In a normal practical case only 5 external capacitors of which
only one is an electrolytic/tantalum filter capacitor .The other capacitor are needed as radio interference suppression
capacitor over the line, one capacitor in the side-tone balancing network and one capacitor for low frequency cut-off
in each of the transmitting and receiving amplifiers. The frequency response is except for that, flat for both amplifiers.
The circuit will with external components get a very good return loss behavior both against purely resistive lines as
for instance 600 Ω and against complex networks as 900 Ω in parallel with 30nF.
To get a good CMRR the microphone input is balanced.
It is possible to add a push-button controlled cut-off of the transmitting amplifier to the circuit without any
disturbance of the other circuit functions
A mute input is included in the circuit. It gives:
1. Cut-off the microphone amplifier.
2. Reduced gain in the receiving amplifier.
3. Connection of the DTMF input.
The receiver amplifier is equipped with a high impedance input stage. This gives a less expensive RC-network on
the input.
Only resistive elements are used to set the receiving gain.
A push-pull power stage in the receiving amplifier gives a high output swing.
To get the extended low current and voltage range two resistors have to be connected from microphone input to
ground.
The side-tone balanced can be set by a RC-network without influence on other parameters. An inexpensive
solution requires only one capacitor while more capacitors can give better performance.
In fig.4①②③ and ④ are RC-links with the following functions:
1. For radio interference suppression and to give the correct return loss behavior.
2. To set the gain and frequency response for transmitting.
3. To set the gain and frequency response for receiving.
4. To set the side-tone level
A stabilized DC output, with a pre-set output voltage of 2.35 Volts, is provided to facilitate interfacing to external
COMS dialer ICs. The voltage is adjustable with two resistors, as indicated in figure 5. The output requires some
filtering to avoid distortion on the telephone line. Note that a high current consumption of the external device will
alters the DC characteristics of the speech circuit.
+Line
1
3
AM
2
AR
AT
4
Transmitting
cut-off
-Line
Mute
Figure 4. Block interconnections
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FUNCTIONAL DESCRIPTION(Cont.)
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LINEAR INTEGRATED CIRCUIT
APPLICATION INFORMATION
Refer to figure 6.
Gain regulation (R1, R2):
These resistors set the starting point for the gain-and side tone regulation.
Input impedance pin 6 is about 5.5 kΩ±20%.
Below are some typical values for R1 and R2, for some different supplies from telephone stations.
Battery feed
R1
R2
R6
No regulation
Set for short line gain.
22kΩ
47~100Ω
All feedings
Regulation:
47Ω
∞
∞
48V, 2·200Ω
75Ω
∞
∞
48V, 2·400Ω
100Ω
180kΩ
36V, 2·500Ω
Impedance to line (R3, C1, C2):
C1 in series with R3 and those in parallel with C2 give the impedance to the line from the set.
C2 must normally be there for the interference too.
The network is optimized with regard to the return loss.
The time constant R3, C1 cannot be allowed to be too small. If the time constant is to small, distortion at low
frequencies may be generated.
If R3 is changed this will change the DC-characteristic too, which set by the voltage at pin 4. The input current at pin
4 is about 1mA
Microphone selection (M1, R16):
The microphone can be either dynamic, magnetic or electrets. See figures 12,14 and 15.
The input impedance between pin 12 and 13 is about 1.7kΩ with typical variation ±20%
Transmitting gain and frequency response (R4, R5, C3, C4):
The network gives the amplification and frequency response for the transmitter. R5 is used when a greater
reduction of the gain is wanted. Input impedance at pin 3 is about 17 kΩ with typical variation ±20%.The sum of the
resistors R4 and R5 must not be less than 35 kΩ because of DC-current to ground. Below is some simple variations
of this network. (See figure 7).
DC-characteristics (R6):
Sets the DC-characteristic and take care of some of the supplied power. The resistor have also function with the
protection of the circuit, the transmitter, the gain regulation and side tone. Common values are 47 Ω to 100 Ω.
Side tone level, receiving gain and frequency response.(R7,R8,R9,R10,R11,C5):
The network sets the side tone balance. The network in the application is one of many possibilities. R10 and R11
balance together the signals that go two different ways from the transmitter output stage one from pin1 and the other
from pin2. The balance network consist of R8, R9 and C5.
The example is not optimized to any specified line, it is only given to show the principle.
Fig8, 9 and 10 are examples of balance networks. Fig.10 is especially suited for lines with high current supply.
R12, R13, C6, (R10, R11):
The networks gives the gain and frequency response for the receiver.
Input impedance at pin 15 is about 38 kΩ with a typical variation of ±20%.For different possibilities for the design
of the network, see the network for the transmitter (R4, R5, C3)
REC, R14:
R14 generates the output impedance to the magnetic earphone (fig.11). If a dynamic earphone is used it should
be placed between pin 17 and 18.See figure 16.
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LINEAR INTEGRATED CIRCUIT
APPLICATION INFORMATION(Cont.)
R15:
This resistor is used to set the driving capability of the receiver output amplifier. Common values are 0 Ω to 50 Ω.
Setting it for low driving capability results in function at lower line current. Breaking up pin 16 will give lower power
consumption and total mute of the receiver when muting the circuit. Disconnecting pin 15 will of cause also give total
receiver mute.
D1, D2, D3, D4, D5:
Rectifier bridge and over voltage protector. The zener voltage at D5 should be as low as possible. Common values
are between 12V~16V.
RDC1, RDC2:
Refer to figure 5.
The pre-set output voltage of 2.35V can easily, if needed, be changed to another value by applying one or two
resistor(RDC1,RDC2) in parallel with the internal resistors (each 15kΩ+/-20%).It is possible to get a rather high voltage
and current from the DC-supply as long as the high current and voltage is available from the line. The DC voltage
has to be filtered by a capacitor and this can, at high DC-voltage and low line current, interfere with the signal on the
line and cause distortion. You can minimize the interference, with a resistor in series with the filter capacitor. The DC
voltage will, of course, be more dependent of the DC-supply current. The DC-output pin has a very low input leak
current, to allow stand-by feeding of the dialer. It is also possible to use pin 9 to feed microphones etc. that do not
need stand-by feeding, without interfering with the stand-by feeding on pin 8. Note that a high current consumption
by the external device will alter the DC characteristics of the speech circuit
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LINEAR INTEGRATED CIRCUIT
APPLICATION INFORMATION(Cont.)
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APPLICATION INFORMATION(Cont.)
DESIGN PROCEDURE:
1. Circuit impedance to the line.
2. DC-characteristic
3. Gain regulation.
4. Transmitter gain and frequency response.
5. Receiver gain and frequency response.
6. Side-tone.
7. Components to suppress radio interference, specially the wires up to the handset.
Others:
The circuit can be placed either in the telephone or in the handset.
Cut off the transmitter can be done at F1 without interference of other functions of the circuit.
When using the extended low current and low voltage range (5mA, 2V), two resistors have to be connected from the
microphone inputs to ground as shown in figure 13.
11
11
3
3
2
15
RA
RA
CA
CA
RA
RB
CB
11
RA
R6
11
3
3
RB
2
RA
CA
3
11
CA
RA
RB
3
RA
11
RB
CA
RB
R10 +Line
RB
3
R6
CA
CB
R11
CB
RA
RA
15
2
CA
RB
11
CA
RC
3
CA
RA
R10 +Line
R11
RB
RB
CB
RB
R6
11
15
RA
CA
CB
R10 +Line
R11
RC
CA
Figure 8. Examples of network "4"
CB
Figure 7. Examples of network "2"
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LINEAR INTEGRATED CIRCUIT
APPLICATION INFORMATION(Cont.)
„
+Line
R10
+Line
2
C6
R12
Zbal
15
2
R11
RA
C6
R12
RB
R6
Rc
15
R6
C
Low impedance
network.
* To get flat response
for receiving
Figure 10. Sidetone network especially
suited for applicatons with a high line
current,when R6 has a low value
Figure 9. Typical sidetone network
4
R14
17
200Ω
200Ω
1μF
1μF
12
13
18
14
Figure11. Magnetic reciever connection
Figure 12. Electret microphone with FET buffer
12
12
MIC
13
50k
11
AM
50k
-Line
Figure 13. Additional components for
extended low current/voltage oeration
Figure 14. Connection of a magnetic
microphone
12
17
13
18
Figure 15. Connection of a dynamic microphone
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Figure 16. Dynamic reviever connection
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LINEAR INTEGRATED CIRCUIT
UTC assumes no responsibility for equipment failures that result from using products at values that
exceed, even momentarily, rated values (such as maximum ratings, operating condition ranges, or
other parameters) listed in products specifications of any and all UTC products described or contained
herein. UTC products are not designed for use in life support appliances, devices or systems where
malfunction of these products can be reasonably expected to result in personal injury. Reproduction in
whole or in part is prohibited without the prior written consent of the copyright owner. The information
presented in this document does not form part of any quotation or contract, is believed to be accurate
and reliable and may be changed without notice.
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