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Электронный компонент: L38812

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UTC L388 12 LINEAR INTEGRATED CIRCUIT

UTC
UNISONIC TECHNOLOGIES CO. LTD
1
QW-R108-013,A
VOICE-SWITCH CIRCUIT FOR
HANDSFREE SPEAKERPHONE
TAM
DESCRIPTION
The UTC L388 12 contains all the necessary circuitry,
amplifiers, detectors, comparators and control functions to
implement a high performance, voice-switched, "hands-free"
function in an answering machine.
The UTC L 388 12 is designed for answering machines
that are either powered from the telephone line or from a
mains powered dc. supply.
Filtering of both the audio and control signals in both
transmitter and receiver channels possible.
An external loudspeaker amplifier has to be used, normally
the same as used for the answering machine.

FEATURES
*Settable gain dynamics (25 or 50dB)
*Low power consumption, totally 1.0mA at 3.3V typical.
*Background noise compensation in the transmitting channel
*
with hold function.
*Excellent noise performance.
*Both channel input amplifiers have balanced inputs.
*Minimum of external components needed for function.
DIP-18
SOP-16
PIN CONFIGURATION
16-pin SO package
1
16
15
14
12
13
11
9
2
3
4
5
6
7
8
10
CTR
-Txin
+Txin
F2out
Txout
TxDetin
TxDetout
NDet
GND
+V
-Rxin
F5out
Rxout
RxDetin
RxDetout
CMP
1
16
15
14
12
13
11
2
3
4
5
6
7
8
10
9
17
18
F2out
Txout
TxDetin
TxDetout
N Det
CMP
RxDetout
Rxout
Rx Detin
+Txin
-Txin
CTR
NC
GND
+V
-Rxin
+Rxin
F5out
18-pin DIP package
UTC L388 12 LINEAR INTEGRATED CIRCUIT

UTC
UNISONIC TECHNOLOGIES CO. LTD
2
QW-R108-013,A
PIN DESCRIPTIONS
16-pin
SO
18-pin
DIP
SYMBOL DESCRIPTION
1
16
CTR
Control input for gain dynamics (25 or 50dB), mute and disable.
2
17
-Txin
Transmitter channel negative input. Input impedance 3k.
3
18
+Txin
Transmitter channel positive input. Input impedance 100k.
4
1
F2out
Output of the second amplifier in the transmitter channel.
5
2
Txout
Transmitter channel output. Min. ac load impedance 10k.
6
3
TxDetin
Input of the transmitter channel signal detector. Input impedance 13k.
7 4
TxDetout
Output of the transmitter channel signal detector. Goes negative referred
to the internal ref. voltage of app.2V when a transmitter signal is present.
8 5 NDet
Background noise detector output. Goes positive referred to the internal
ref. Voltage of app.2V when a background noise signal is present.
9 6 CMP
Comparator input..
Summing point to the different Detector outputs.
10 7
RxDetout
Output of the receiver channel signal detector. Goes positive referred to
the internal ref. Voltage of app.2V when a receiver signal is present
11
8
RxDetin
Input of the receiver channel signal detector. Input impedance 13k.
12
9
Rxout
Receiver channel output. Min. ac load impedance 10k.
13
10
F5out
Output of the second amplifier in the receiver channel.
11
+Rxin
Receiver channel positive input. Input impedance 140k.
14
12
-Rxin
Receiver channel negative input,Input impedance 20k.
15 13 V+
Supply of the speech switching circuitry. A shunt regulator, voltage
apprx. 3.3V at 1.0mA.
16 14 GND
System
ground.
15 NC
Not
connected.

BLOCK DIAGRAM(16-pin SO package)
1
13
16
12
11
14
10
9
7
8
3
2
15
6
4
5
F3
F2
-
+
F6
F5
F4
Ref.
Control
F1
+
+

UTC L388 12 LINEAR INTEGRATED CIRCUIT

UTC
UNISONIC TECHNOLOGIES CO. LTD
3
QW-R108-013,A
MAXIMUM RATINGS
PARAMETER SYMBOL RATINGS
UNIT
Speech switch supply current
I
D
10
mA
Voltage Pin 1-14
-0,5 ~ Vpin
15
+0.5
V
Operating temperature
T
opr
-20 ~ +70
Storage temperature
Tstg
-55 ~ +125

TEST CIRCUIT
L388 12
RxDetin 11
RxDetout 10
15 V
+
GND
16
100nF
V
Ref
V
+
I
D
ISOLATION AND MEASUREMENT OF V
R
ef
L388 12
I
D
15
5
6
4
3
2
8
7
9
10
1
16
12
11
13
14
100F/16V
+
Txout
V+
Tx
Detin
F2
out
+Tx
in
-Txin
N
Det
Tx
Detout
CMP Rx
Detout
CTR
-Rx in
F5out
Rx
Detin
Rxout
GND
V
+
10F
R
Txout
V
Txout
+
10F
+
C
Tx
F2out
RF2out
V
Txin
1F
+
4.7F
I
Txin
V
NDet
V
TxDet
V
CMP
V
RxDet
V
CTR
I
NDet
I
TxDet
CTxDet
+
0.1F
C
RxDet
+
I
RxDet
R
CTR
I
CTR
V
Rxin
I
Rxin
1F
+
R
F5out
F5out
10F
+
C
RX
R
Rout
V
Rout
10F
+
+

ELECTRICAL CHARACTERISTICS
(Ta=25,f=1kHz, R
CTR
=0,C
TxDet
=0,R
Tx
out=
,R
RXout
=
,R
F2
out=
, R
F5
out=
,R
TX
=0,R
RX
=0,C
RxDet
=0 and
I
D
=1.0mA unless otherwise noted)
PARAMETER TEST
CONDITIONS
MIN
TYP
MAX
UNIT
Speech control section
Terminal voltage, V
+
I
D
=1.0mA
3.3
V
Internal reference voltage, V
R
ef
1.96
V
Frequency response for all amplifiers
200-3400Hz,Relative 1 kHz
-1
1
dB
Transmit gain, 20Iog(V
Txout
/V
Txin
)
V
CMP
=V
R
ef
-0.1V
V
CMP
=V
R
ef
+0.1V
V
CMP
=V
R
ef
-0.1V R
CTR
=100k,V
CTR
=V+
V
CMP
=V
R
ef
+0.1V R
CTR
=100k,V
CTR
=V+
41.5
41.5
44
-6
44
19
-3.5
21.5
dB
dB
dB
dB
Receive gain, 20Iog(V
R
xout/V
R
xin)
V
CMP
=V
R
ef
+0.1V
V
CMP
=V
R
ef
-0.1V
V
CMP
=V
R
ef
+0.1V R
CTR
=100k,V
CTR
=V+
V
CMP
=V
R
ef
-0.1V R
CTR
=100k,V
CTR
=V+
26.5
26.5
29
-21
29
4
-18.5
6.5
dB
dB
dB
dB
Max transmit detector gain,
20Iog(V
T
xdet/V
T
xin)
V
TxDet
<200mV
P
,C
TX
=100nF
V
CMP
=V
R
ef
+0.1V
V
CMP
=V
R
ef
-0.1V

37

67.5
42.5
dB
dB
Max transmit detector gain,
20Iog(V
R
xdet/V
R
xin)
V
RxDet
<200mV
P
,C
TX
=100nF
V
CMP
=V
R
ef
+0.1V
V
CMP
=V
R
ef
-0.1V

22.5
53
28
dB
dB
Background noise rectifier gain,(note 1) V
CMP
=V
R
ef
-0.1V,C
txdet
=1F
V
CMP
=V
R
ef+
0.1V,C
txdet
=1F
6.0
Hold
dB
UTC L388 12 LINEAR INTEGRATED CIRCUIT

UTC
UNISONIC TECHNOLOGIES CO. LTD
4
QW-R108-013,A
PARAMETER TEST
CONDITIONS
MIN
TYP
MAX
UNIT
+Tx
In
input impedance
80
100
120
k
-Tx
In
input impedance
2.4
3.0
3.6
k
-Rx
In
input impedance
16
20
24
k
Tx
out
ac, load impedance
10
k
Rx
out
ac, load impedance
10
k
F2
out
ac, load impedance
10
k
F5
out
ac, load impedance
10
k
Transmitter channel output swing, V
TXOut
2% distortion, R
Txout
=R
Rxout
=25 k
500 mV
p
Receiver channel output swing, V
RxOut
2% distortion, R
Txout
=R
Rxout
=25 k
500 mV
p
Transmitter output noise, V
TxOut
V
CMP
=V
R
ef
-0.1V,v
TXIn
=0V
-75
dB
psof
Receiver output noise, V
RxOut
V
CMP
=V
R
ef
+0.1V,v
RXIn
=0V
-75
dB
A
Tx
Det
sink current, I
TxDetOut
V
txDetIn
=V
R
ef
+0.1V
-6.0
-2.5
mA
Rx
Det
source current, I
RxDetOut
V
RxIn
=V
R
ef
-0.1V 2.5
6.0
mA
T
xDet
source current, I
TxDet
V
CMP
=V
R
ef
-0.1V
30
A
Rx
Det
sink current, I
RxDetOut
V
RxDetIn
=V
R
ef
+0.1V -30
A
Tx
Det
swing relative to V
Ref
, V
TxDetOut
V
TxDetIn
=V
R
ef
+0.1V (note
2)
-0.7
V
Rx
Det
swing relative to V
Ref
, V
RxDetOut
V
RxDetIn
=V
R
ef
-0.1V (note
2) +0.7
V
N
Det
sink current (fast charge), I
NDet
V
TxDetIn
=V
R
ef
-0.1V
V
CMP
=V
R
ef
-0.1V
-4.5
-1.5
mA
N
Det
source current, I
NDet
V
TxDetIn
=V
R
ef
+0.1V
V
CMP
=V
R
ef
+0.1V
3 5 7
A
N
Det
Ieakage current(hold),I
NDet
V
TxDetIn
=V
R
ef
-0.1V
V
CMP
=V
R
ef
+0.1V
-100 nA
N
Det
swing relative to V
Ref
,V
NDet
V
CMP
=V
R
ef
-0.1V
V
TxDetIn
=V
R
ef
+0.1V
-0.45 V
CMP(comparator) sensitivity,
Transmit(Tx) mode to receive
(Rx) mode or vice versa
Tx mode=max Tx gain,
Rx mode=max Rx gain
50
100
mV
CTR voltage for 25 dB dynamics,V
CTR
V
CMP
=V
R
ef
+0.35V,R
CTR
=100k
V
+
V
CTR voltage for mute,I
CTR
V
CMP
=V
R
ef
+0.35V
A
CTR voltage for disable,V
CTR
0.55
V


Notes:
V
NDet
-V
R
ef
1. 20
log ( )
V
TxDet
-V
TxDetO
V
NDet
=voltage at noise detector output
V
R
ef
=reference voltage (about 1.9V)
V
TxDet
=Voltage at transmit detector output
V
TxDetO
=voltage at transmit detector at the point
when the voltage at the noise detector starts
moving when a signal at transmit channel input is
gradually increased (threshold, typical value 30 mV)
2.
Depends on V
+.
Channels are tracking.

UTC L388 12 LINEAR INTEGRATED CIRCUIT

UTC
UNISONIC TECHNOLOGIES CO. LTD
5
QW-R108-013,A
FUNCTIONAL DESCRIPTION SPEECH CONTROL SECTION
Transmitter and Receiver Channels
The transmitter and receiver channels consist of three amplifying stages each, F1,F2,F3 and F4,F5,F6.The inputs
of the amplifiers must be ac. coupled because they are dc. vise at the internal reference voltage(2V) level. F1 and
F4 are fixed gain amplifiers of 30,5 dB and 15.5 dB respectively, while the rest of them are of controlled gain type.
The gain of F2,F3 as well as F5 and F6 is controlled by comparators. The comparator receives its information partly
from the summing point of the transmitter, receiver and background noise detectors at CMP input and partly through
the control input, CTR, which controls the gain dynamics (25 or 50 dB). Amplifiers F2 and F3 have the maximum
gain when the transmitter channel is fully open, consequently the amplifiers F5 and F6 will have minimum gain and
vice versa. See figure.1 and figure. 9.
The positive input on transmitter and the negative input on receiver channel has a rather high input impedance. It
renders a good gain precision and noise performance when used with low signal source impedance. The differential
input of the transmitter channel can be used to suppress unwanted signals in the microphone supply, see figure. 5.
Signal Detectors and Comparator
The signal detectors sense and rectify the receiver and microphone signals to opposite polarities referenced to the
internal reference voltage of approx. 2V.The voltage at RxDet will go positive and at TxDet negative in the presence
of a signal at the respective channel input. In the idle(no signal) state, the voltages at RxDet, TxDet and CMP are
equal to the internal reference voltage. Signal at Txin will result in an decreasing level at TxDetout and hence also at
CMP input. the transmitter channel and decrease it in the receiver channel. Signal at Rxin will do vice versa. The
voltages RxDetout and TxDetout controlthus the gain setting in respective channel through the comparators using
the CMP input as a summing point with an input current of less than 1A. The attack time in the receiver channel is
set by C2 together with C1 and either by the maximum current capability of the detector output or it with R2 added.
The transmitter channel works likewise. See figure.5.
The decay time in the receiver and transmitter channels is set by C2 and C3 respectively. The resistor in the time
constant is formed by an internal 200kresistor in parallel with the external resistors R3 and R4 respectively. The
influence of eventual R1 and R2 can be omitted.
The text above describes the case when only one channel is open at a time and there is a distinctive pause
between signals at receiver and transmitter channel inputs so the circuit will have time to reach its idle state. See
figure.10 A) to E). If one of the channels gets an input signal immediately after the signal has disappeared from the
other channel input the effective decay time , as the CMP input sees it, will be shorter than in the first case. See
figure.10 F) to G). The capacitor C4 at CMP -input sets the speed of the gain change in the transmitter and receiver
channels. The capacitors C2 and C3 should be dimensioned for a charging time of 0.5-10mS and for a discharge
time of 150-300mS. The question of switching times being a highly subjective proposition, is in large dependent of
the language being spoken in the system , caused by the varying sound pressure picture of the different languages.
A hysteresis effect is achieved in the switching since the level detectors sense the signals after F2 and F5
respectively (F2 and F5 are affected by the gain setting). For example: If the transmitter channel is open (maximum
gain),a smaller signal at Txin is enough to keep the channel open than would be necessary to open it when the
receiver channel is open. The output swing of the level detectors is matched for variations in the supply voltage. The
detectors have a logarithmic rectifier characteristic whereby gain and sensitivity is high at small signals. There is a
break point in the curve at a level of + 200mV from the internal reference voltage app.2V,where the sensitivity for
increasing input signals decreases with factor of 10, increasing the detectors dynamic range. See figure.8.

Background Noise Detector
The general function of the background noise detector in the transmitting channel is to create a positive signal (in
respect to the reference) so that, when coupled to the summing point at the CMP input, will counteract the signal
from the transmitter level detector representing the actual sound pressure level at the microphone. This counteracts
the noise from influencing the switching characteristics. The input signal to the background noise level detector is
taken from the output of the transmitter detector, a voltage representing the envelope of the amplified microphone
signal. The detector inverts and amplifies this signal 2 X (transmitting mode) and has on it is output a RC network
consisting of an internal resistor of 100k and an external capacitor C4.The voltage across C4 is connected to the
CMP input (summing point) via a resistor R5.The resistor R6 is important in order to keep the charging current of C4
within safe limits in regard of high charge peaks that could be audible in the system. The extent to which the NDet
UTC L388 12 LINEAR INTEGRATED CIRCUIT

UTC
UNISONIC TECHNOLOGIES CO. LTD
6
QW-R108-013,A
output will influence the potential at CMP input is set by the gain of the detector, the maximum swing and R5.If a
continuous input signal is received from the microphone (>10sec.) the voltage across C4 is pulled negative(relative
to the reference)with a time constant set by C4 to e.g.5 sec. A continuous input signal is thus treated as noise. Since
the output of the noise detector is going negative it thereby counteracts the signal from the transmitter detector and
thus helping the receiver detector signal to maintain a set relation to the transmitter detector signal If the transmitter
input signal contains breaks like breath pauses the voltage at TxDetout decreases. If the voltage across C3 gets less
than the inverted voltage across C4 divided by the detector gain a rapid charge of C4 towards reference will follow
(all levels referred to the reference).If the breaks are frequent as in speech the background detector will not influence
the switching characteristic of the system. See figure.9. There is a threshold of approx. 50mV at TxDetout to prevent
the activation of background noise detection in noiseless environment. In the receiver mode some of the
loudspeaker output signal will be sensed by the microphone. In order not to treat this input signal as noise, the noise
detector goes into a hold state and "remembers" the level from the previous transmitting mode periode.

CTR Input
For full speech control (50dB attenuation between the channels) this input can be left unconnected. To set the
function to 25dB attenuation the input has to be higher than 600mV below V+. See figure 11. To set the circuit into a
mute state(results in, reduced gain in receiver channel for the DTMF confidence tone in the loudspeaker and closed
transmitter channel) a voltage below Vref has to be connected to the input. By lowering the voltage at the input
below 0.9V a condition will emerge where both receiver and transmitter channels are closed. See figure.4 and 9.
1
13
16
12
11
14
10
9
7
8
3
2
15
6
4
5
F3
F2
-
+
F6
F5
F4 -
Control
L388 12
CTR
Txout
V+
-Txin
+Txin
+
N
Det
C4
+
+
+
C3
C1
C2
R5
TxDet CMP PxDet
Rxi
n
GND
Rxout
16
3
2
F2
-
+
F5
L388 12
Tx
V
Txin
100k
100k
3k
3k
-
+
120k
120k
20k 14
Ref.
I
Rx
V
Rxin
Figure 2. Receiver and transmitter channel input arrangement
Figure 1. Passive networks setting the speech control function
F1
F1
F4
Ref.
C
1
13
16
12
11
14
10
9
7
8
3
2
15
6
4
5
F3
F2
+
F6
F5
F4 -
Control
L388 12
CTR
Txout
-Txin
+Txin
+
N
Det
C4
+
+
+
C3
C1
C2
R5
TxDet CMP
PxDet
Rxin
GND
Rxout
C
C
C
+
Transmitter
channel output
R
+L
R
R
R
C
+
Mic.
C
C
Power
amplifier
input
P1
Receiver
input
R
C
C
R
Figure 3. Speech switching arrangement
F1
-
Ref.
UTC L388 12 LINEAR INTEGRATED CIRCUIT

UTC
UNISONIC TECHNOLOGIES CO. LTD
7
QW-R108-013,A
L388 12
I
D
=1mA
+V
+
The circuit has a buit in shunt voltage
generator.It needs a minimum 1mA
current for its function.The voltage at
this current will be 3.3V.If the voltage
+V is not constant care must be taken
so that the I
D
will not exeed 10 mA
Figure 4. Circuit supply function
15
F2
- +
R7
R6
R5
C4
Mic.
C1
C2
C3
+
16
2
3
R2
R4
R3
Ref.
R1
Figure 5. Transmitter channel input amplifier used
to suppress ripple in the mic.supply.(CMRR).
+600
+400
+200
Vref
-200
-400
-600
Vref=2V
V
TxDet
V
RxDet
V
Rxin
mV
p
V
Txin
Figure 6. Transmitter and receiver channel
rectifier characteristics.
F1
R1=R2=3k
R3=R4=100k
R5=R6
C1=C2
10
7.5
5.0
2.5
1.5
1.0
0.5
Txin
TxDetout
N
Det
Figure 7. Relationship in timing between
the voltage levels at Tx
IN
,Tx
Det
and N
Det
Figure 8. Transmitter and receiver channel output dynamics.
500
100
200
300
400
3.4
3.2
3.0
2.8
2.6
2.4
V
Txout
(mV)
V+(V)
500
100
200
300
400
3.4
3.2
3.0
2.8
2.6
2.4
(mV)
V+(V)
V
Rxout
~ ~
~ ~
40
30
20
10
0
-60 -40
-20
0
20
40
60
-20
-10
0
10
20
30
Transmit
gain=
Receive
gain=
VCTR=V+
VCTR=V+
VCTR=open
VCTR=open
V
CTR
= V
REF
dB
dB
V
CMP
- V
REF
mV
Figure 9. Transmit and reveive gain as a
function of VCMP and VCTR
Rxdet
Txdet
CMP
Full transmit level
A
B
C
D
E
F
G
Figure 10. Timing of the transmitter and receiver
channels at the CMP-input
Full recieve level
UTC L388 12 LINEAR INTEGRATED CIRCUIT

UTC
UNISONIC TECHNOLOGIES CO. LTD
8
QW-R108-013,A
25 dB speech
control
50 dB speech
control
DTMFMute
Total mute
0
3
2
1
Vref
Mode
Figure 11. Control modes as function of voltage applied to
gain dynamics control input CTR;I
D
=1mA























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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
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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.