L38812 [UTC]
LINEAR INTEGRATED CIRCUIT; 线性集成电路
| 型号： | L38812 |
| 厂家： | 
Unisonic Technologies |
| 描述： | LINEAR INTEGRATED CIRCUIT |
| 文件： | 总8页 (文件大小：179K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
UTC L388 12 LINEAR INTEGRATED CIRCUIT
VOICE-SWITCH CIRCUIT FOR
HANDSFREE SPEAKERPHONE
TAM
SOP-16
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.
DIP-18
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.
PIN CONFIGURATION
18-pin DIP package
16-pin SO package
F2out
Txout
18
17
16
15
14
13
12
11
10
+Txin
-Txin
CTR
NC
1
2
3
CTR
-Txin
+Txin
F2out
16 GND
+V
1
2
3
4
5
6
15
14
13
12
11
10
9
TxDetin
-Rxin
TxDetout
4
5
6
F5out
N Det
CMP
GND
+V
Txout
TxDetin
Rxout
RxDetin
-Rxin
+Rxin
RxDetout
Rx Detin
7
8
9
TxDetout
7
8
RxDetout
CMP
NDet
Rxout
F5out
1
UTC UNISONIC TECHNOLOGIES CO. LTD
QW-R108-013,A
UTC L388 12 LINEAR INTEGRATED CIRCUIT
PIN DESCRIPTIONS
16-pin
18-pin
DIP
16
17
18
1
SYMBOL
DESCRIPTION
SO
1
CTR
-Txin
+Txin
F2out
Txout
TxDetin
Control input for gain dynamics (25 or 50dB), mute and disable.
Transmitter channel negative input. Input impedance 3kΩ.
Transmitter channel positive input. Input impedance 100kΩ.
Output of the second amplifier in the transmitter channel.
Transmitter channel output. Min. ac load impedance 10kΩ.
Input of the transmitter channel signal detector. Input impedance 13kΩ.
Output of the transmitter channel signal detector. Goes negative referred
to the internal ref. voltage of app.2V when a transmitter signal is present.
Background noise detector output. Goes positive referred to the internal
ref. Voltage of app.2V when a background noise signal is present.
Comparator input..
2
3
4
5
2
3
6
7
4
5
6
7
TxDetout
8
NDet
9
CMP
Summing point to the different Detector outputs.
Output of the receiver channel signal detector. Goes positive referred to
the internal ref. Voltage of app.2V when a receiver signal is present
Input of the receiver channel signal detector. Input impedance 13kΩ.
Receiver channel output. Min. ac load impedance 10kΩ.
Output of the second amplifier in the receiver channel.
Receiver channel positive input. Input impedance 140kΩ.
Receiver channel negative input,Input impedance 20kΩ.
Supply of the speech switching circuitry. A shunt regulator, voltage
apprx. 3.3V at 1.0mA.
10
RxDetout
11
12
13
8
9
10
11
12
RxDetin
Rxout
F5out
+Rxin
-Rxin
14
15
16
13
V+
14
15
GND
NC
System ground.
Not connected.
BLOCK DIAGRAM(16-pin SO package)
1
5
12
16
Control
F3
F6
F5
13
11
4
6
15
+
F2
2
3
14
-
+
F4
F1
Ref.
+
9
10
8
7
2
UTC UNISONIC TECHNOLOGIES CO. LTD
QW-R108-013,A
UTC L388 12 LINEAR INTEGRATED CIRCUIT
MAXIMUM RATINGS
PARAMETER
Speech switch supply current
Voltage Pin 1-14
SYMBOL
ID
RATINGS
10
-0,5 ~ Vpin15+0.5
-20 ~ +70
UNIT
mA
V
℃
Operating temperature
Storage temperature
Topr
Tstg
-55 ~ +125
℃
TEST CIRCUIT
+
V+
100μF/16V
15
ID
GND 16
12
+
V+
5 Txout
10μF
+
VTxout
VRout
RRout
Rxout
10μF
RxDetin 11
RTxout
6
RxDetin 11
TxDetin
100nF
ID
CTx
L388 12
9
CRX
10μF
10μF
15 V+
L388 12
+
+
F2out
4
F2out
+Txin
F5out
RF5out
F5out 13
1μF IRxin
+
ITxin
4.7μF
RF2out
+
-Rx in
14
V+
3
2
VRef
RxDetout 10
GND
16
RxDetout CTR
10
NDet TxDetout CMP
-Txin8
7
1
+
CTxDet
1μF
CRxDet
+
0.1μF
VTxin
VRxin
+
RCTR
ICTR
ISOLATION AND MEASUREMENT OF VRef
ITxDet
IRxDet
INDet
VNDet
VTxDet VCMP VRxDet VCTR
ELECTRICAL CHARACTERISTICS
(Ta=25℃,f=1kHz, RCTR=0,CTxDet=0,RTxout= ∞,RRXout= ∞,RF2out= ∞, RF5out= ∞,RTX=0,RRX=0,CRxDet=0 and
ID=1.0mA unless otherwise noted)
PARAMETER
Speech control section
Terminal voltage, V+
TEST CONDITIONS
ID=1.0mA
MIN
TYP MAX UNIT
3.3
V
Internal reference voltage, VRef
Frequency response for all amplifiers
Transmit gain, 20·Iog(VTxout/VTxin)
1.96
V
200-3400Hz,Relative 1 kHz
VCMP=VRef-0.1V
-1
41.5
1
dB
dB
dB
dB
dB
dB
dB
dB
dB
44
-6
VCMP=VRef+0.1V
-3.5
21.5
-18.5
6.5
VCMP=VRef-0.1V RCTR=100k,VCTR=V+
VCMP=VRef+0.1V RCTR=100k,VCTR=V+
VCMP=VRef+0.1V
41.5
26.5
26.5
44
19
29
-21
29
4
Receive gain, 20·Iog(VRxout/VRxin)
VCMP=VRef-0.1V
VCMP=VRef+0.1V RCTR=100k,VCTR=V+
VCMP=VRef-0.1V RCTR=100k,VCTR=V+
VTxDet<200mVP ,CTX=100nF
VCMP=VRef+0.1V
Max transmit detector gain,
20·Iog(VTxdet/VTxin)
67.5
42.5
dB
dB
VCMP=VRef-0.1V
37
Max transmit detector gain,
VRxDet<200mVP ,CTX=100nF
20·Iog(VRxdet/VRxin)
VCMP=VRef+0.1V
53
28
6.0
Hold
dB
dB
dB
VCMP=VRef-0.1V
VCMP=VRef-0.1V,Ctxdet=1μF
VCMP=VRef+0.1V,Ctxdet=1μF
22.5
Background noise rectifier gain,(note 1)
3
UTC UNISONIC TECHNOLOGIES CO. LTD
QW-R108-013,A
UTC L388 12 LINEAR INTEGRATED CIRCUIT
PARAMETER
TEST CONDITIONS
MIN
TYP MAX UNIT
kΩ
kΩ
kΩ
kΩ
kΩ
kΩ
kΩ
+TxIn input impedance
80
100
3.0
20
120
3.6
24
-TxIn input impedance
-RxIn input impedance
Txout ac, load impedance
Rxout ac, load impedance
F2out ac, load impedance
F5out ac, load impedance
2.4
16
10
10
10
10
2% distortion, RTxout=RRxout=25 kΩ
2% distortion, RTxout=RRxout=25 kΩ
VCMP=VRef-0.1V,vTXIn=0V
VCMP=VRef+0.1V,vRXIn=0V
VtxDetIn=VRef+0.1V
VRxIn=VRef-0.1V
Transmitter channel output swing, VTXOut
Receiver channel output swing, VRxOut
Transmitter output noise, VTxOut
Receiver output noise, VRxOut
TxDet sink current, ITxDetOut
RxDet source current, IRxDetOut
TxDet source current, ITxDet
500
500
-75
-75
-6.0
6.0
mVp
mVp
dBpsof
dBA
mA
mA
μA
μA
-2.5
30
2.5
-30
VCMP=VRef-0.1V
RxDet sink current, IRxDetOut
VRxDetIn=VRef+0.1V
VTxDetIn=VRef+0.1V
VRxDetIn=VRef-0.1V
VTxDetIn=VRef-0.1V
VCMP=VRef-0.1V
VTxDetIn=VRef+0.1V
VCMP=VRef+0.1V
VTxDetIn=VRef-0.1V
VCMP=VRef+0.1V
VCMP=VRef-0.1V
TxDet swing relative to VRef, VTxDetOut
RxDet swing relative to VRef, VRxDetOut
NDet sink current (fast charge), INDet
(note 2) -0.7
(note 2) +0.7
-4.5
V
V
mA
-1.5
7
μA
nA
V
NDet source current, INDet
3
5
NDet Ieakage current(hold),INDet
NDet swing relative to VRef,VNDet
-100
-0.45
50
VTxDetIn=VRef+0.1V
Tx mode=max Tx gain,
Rx mode=max Rx gain
CMP(comparator) sensitivity,
Transmit(Tx) mode to receive
(Rx) mode or vice versa
CTR voltage for 25 dB dynamics,VCTR
CTR voltage for mute,ICTR
100
mV
VCMP=VRef+0.35V,RCTR=100kΩ
VCMP=VRef+0.35V
V+
V
μA
CTR voltage for disable,VCTR
0.55
V
Notes:
VNDet-VRef
1. 20· log (
)
VTxDet-VTxDetO
VNDet=voltage at noise detector output
VRef=reference voltage (about 1.9V)
VTxDet=Voltage at transmit detector output
VTxDetO=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.
4
UTC UNISONIC TECHNOLOGIES CO. LTD
QW-R108-013,A
UTC L388 12 LINEAR INTEGRATED CIRCUIT
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 1μA. 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 200kΩresistor 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
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UTC UNISONIC TECHNOLOGIES CO. LTD
QW-R108-013,A
UTC L388 12 LINEAR INTEGRATED CIRCUIT
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
5
12
16
L388 12
L388 12
Rxout
GND
CTR
Txout
Control
I
F3
F2
F6
F5
F2
F5
F4
Ref.
13
11
4
6
15
120k
120k
+
V+
+
100k
3k
100k
-F1+
-
2
3
2
3
20k
-Txin
+Txin
14
-
Rxi
n
14
F4 -
Rx
F1
3k
Tx
+
Ref.
10
16
8
7
9
VRxin
VTxin
NDet
R5
TxDet
CMP
PxDet
+
+
+
C4
C3
C1
C2
Figure 1. Passive networks setting the speech control function
Figure 2. Receiver and transmitter channel input arrangement
Power
amplifier
input
Transmitter
channel output
CTR
1
5
R
Rxout
GND
L388 12
C
12
13
11
16
Txout
C
P1
Control
+L
F3
F2
F6
F5
4
Receiver
input
6
R
15
+
+
C
R
R
C
+
R
R
C
2
3
-
14
-Txin
+Txin
F4 -
F1
Ref.
Rxin
+
C
8
7
10
9
C
NDet
TxDet
PxDet
CMP
C
Mic.
C
R5
C3
+
+
+
C4
C1
C2
Figure 3. Speech switching arrangement
6
UTC UNISONIC TECHNOLOGIES CO. LTD
QW-R108-013,A
UTC L388 12 LINEAR INTEGRATED CIRCUIT
L388 12
The circuit has a buit in shunt voltage
ID=1mA
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 ID will not exeed 10 mA
15
+V
+
Figure 4. Circuit supply function
VRxDet
+600
+400
+200
+
F2
F1
Ref.
R3
R4
R7
-
+
2.5
7.5
1.0
VRxin
mV
5.0
10
C2
C1
R6
R5
R2
2
Vref
Vref=2V
p
R1
VTxin
1.5
0.5
16
3
-200
-400
-600
R1=R2=3k
R3=R4=100k
R5=R6
Mic.
C4
C3
C1=C2
VTxDet
Figure 5. Transmitter channel input amplifier used
to suppress ripple in the mic.supply.(CMRR).
Figure 6. Transmitter and receiver channel
rectifier characteristics.
VTxout
(mV)
VRxout
(mV)
Txin
500
400
300
200
100
500
400
TxDetout
NDet
300
200
100
V+(V)
V+(V)
2.4 2.6 2.8 3.0 3.2 3.4
2.4 2.6 2.8 3.0 3.2 3.4
Figure 7. Relationship in timing between
the voltage levels at TxIN,TxDet and NDet
Figure 8. Transmitter and receiver channel output dynamics.
Receive
gain=
Transmit
gain=
dB
dB
30
Rxdet
Txdet
40
30
20
10
20
10
0
VCTR=V+
VCTR=V+
A
B
E
F
Full recieve level
G
C
D
-10
-20
VCTR=open
20 40 60
0
CMP
VCTR=open
VCTR = VREF
Full transmit level
VCMP - VREF
mV
-60 -40 -20
0
Figure 9. Transmit and reveive gain as a
function of VCMP and VCTR
Figure 10. Timing of the transmitter and receiver
channels at the CMP-input
7
UTC UNISONIC TECHNOLOGIES CO. LTD
QW-R108-013,A
UTC L388 12 LINEAR INTEGRATED CIRCUIT
Mode
Vref
25 dB speech
control
50 dB speech
control
DTMFMute
Total mute
2
3
0
1
Figure 11. Control modes as function of voltage applied to
gain dynamics control input CTR;ID=1mA
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.
8
UTC UNISONIC TECHNOLOGIES CO. LTD
QW-R108-013,A
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