Ericsson PBL38571-1NS, PBL38571-1SOS Datasheet

1
PBL 385 71
June 1999
PBL 385 71
High current Speech and
Line interface Circuit
1. Impedance to the line and radio interference suppression
2. Transmitter gain and frequency responce network
4. Sidetone balance network
Figure 1. Functional diagram.
16-pin plastic BW SO
16-pin plastic BW DIP
REC
7
9
14
6
3
2
16
15
1
8
AR
AT
PBL 385 71
+
11
10
AM
+
Mute
(active low)
1
3
2
4
Telephone line
4,5, 12,13.
Description.
PBL 38571 is a monolithic integrated speech transmission circuit for use in electronic telephones and as DECT line interface with balanced in - and output. It is designed to accomodate either a low impedance dynamic microphone or an electret microphone that can be supplied from the circuits own DC - supply. A signal summing point at the transmitter input is available. An internally preset line length compensation can be adjusted with external resistors to fit into different current feed systems as for ex. 48 V, 2 x 200 ohms, 48 V, 2 x 400 ohms and 48 V, 2 x 800 ohms.The line regulation can be shut off in low mode. Application dependent para­meters such as line balance, side tone level, transmitter and receiver gains and frequency responces are set independently by external components which means an easy adaption to various market needs. The setting of the parameters, if carried out in certain order will counteract the interaction between the settings. It features high line current capability on a small footprint. Function compatible with the PBL 3781 family of speech circuits.
Key features.
Minimum number of external components, 5 capacitors and 10 resistors.
Easy adaption to various market needs.
Mute control input for operation with DTMF - generator.
Transmitter and receiver gain regulation for automatic loop loss compensation. Disconnectable.
Extended current and voltage range 5 - 130 mA, down to 2 V.
Differential microphone input for good balance to ground.
Balanced receiver output stage.
In 16 - pin DIP and SO BW batwing packages.
Short start up time.
Excellent RFI performance.
PBL 38571
PBL38571
2
PBL 385 71
Figure 4. Circuit with external compon­ents for test set up.
Maximum Ratings
Parameter Symbol Min Max Unit
Line voltage, tp = 2 s V
L
018V
Line current, continuous, DIP (batwing) package I
L
0 130 mA
Line current, continuous, SO (batwing) package (dependent on mounting) I
L
0 120 mA
Operating temperature range T
Amb
-40 +70 °C
Storage temperature range T
Stg
-55 +125 °C
No input should be set on higher level than pin 6 (+C).
Figure 2. T est set up without rectifier bridge.
Figure 3. T est set up with rectifier bridge.
+
= 350
+ LINE
- LINE
ARTIFICIAL
LINE
I
L
V
2
V
1
V
L
R = 0 - 4k
L
0 ohm when artificial line is used
MUTE
PBL 38571 with external components
See fig. 4
Z
Mic
= 350
Z
Rec
MIC
REC
R
feed
= 400 + 400
600
C
E = 48.5V
V
3
V
4
C = 1µF when artificial line is used 470µF when no artificial line
V
M
5H + 5H
+
I
M
+
+ LINE
- LINE
I
L
V
2
V
1
V
L
R = 0 - 4k
L
MUTE
PBL 38571 with external components
See fig. 4
Z
Mic
Z
Rec
MIC
REC
R
feed
= 400 + 400
600
+
E = 50.0V
V
3
V
4
1µF
V
M
Uz= 15-16V
5H + 5H
= 350
= 350
I
M
REC 350
79
14
6
32
16
15
1
8
AR
AT
PBL 385 71
+
11
10
AM
4,5, 12,13.
310
47nF
2.7k
Mic. 350
R16
Mute
(active low)
910
62k
6.2k910
100nF
18k
R4
C3
R7
R8
R10
R11
R3
R14
+Line
+
15nF
47µF
11k
100nF
11k
560
75
22k
R5
R6
R9
C5
R12
C1
C2
-Line
C6
Rg
3
PBL 385 71
Electrical Characterisics
At T
Amb
= + 25° C. No cable and line rectifier unless otherwise specified.
Ref.
Parameter fig. Conditions Min Typ Max Unit
Line voltage, V
L
2I
L
= 15 mA 3.3 3.7 4.1 V
2I
L
= 100 mA 11 13 15 V Transmitting gain, note 1 2 20 •10 log (V2 / V3); 1 kHz No gain regulation, low mode Rg = 20k 41 43 45 dB Transmitting gain, note 1 2 20 •
10
log (V2 / V3); 1 kHz
With gain regulation R
L
= 0, RG = 41 43 45 dB
R
L
= 400 43.5 45.5 47.5 dB
RL = 900 - 2.2 k 46 48 50 dB Transmitting range of 2 1 kHz, RL = 0 to 900 3 5 7 dB regulation Transmitting frequency 2 200 Hz to 3.4 kHz -1 1 dB response Microphone input impedance 2 1.7//(2.7) note 3 k Transmitter input impedance 2 1 kHz 13.5 17 20.5 k pin 3 Transmitter dynamic output 2 200 Hz - 3.4 kHz 1.5 V
p
2% distortion, IL = 20 - 100 mA Transmitter max output 2 200 Hz - 3.4 kHz 3 V
p
IL = 0 - 100 mA, V3 = 0 - 1 V Transmitter output noise 2 Psoph-weighting, Rel 1 V
rms
, RL = 0 -75 dB
Psoph
Receiving gain, note 1 2 20 • 10 log (V4 / V1); 1 kHz No gain regulation, low mode Rg ™ = 20k -18.5 -16.5 -14.5 dB Receiving gain, note 1 2 20 • 10 log (V4 / V1); 1 kHz With gain regulation R
L
= 0, RG = -18.5 -16.5 -14.5 dB
R
L
= 400 -16 -14 -12 dB
RL = 900 - 2.2 k -13.5 -11.5 -9.5 dB Receiving range of regulation 2 1 kHz, RL = 0 to 900 3 5 7 dB Receiving frequency response 2 200 Hz to 3.4 kHz -1 1 dB Receiver input impedance 2 1 kHz, 38 k Receiver output impedance 2 1 kHz, 3(+310)note 3 Receiver dynamic output 2 200 Hz - 3.4 kHz 0.5 V
p
note 2 2% distortion, IL = 20 - 100 mA Receiver max. output 3 Measured with line rectifier 0.9 V
p
200 Hz - 3.4 kHz, IL = 0 - 100 mA, V1= 0 - 50 V
Receiver output noise 2 A-weighting, Rel 1V
rms
, with cable -85 dB
A
0 - 3 km, Ø = 0.4 mm 0 - 5 km, Ø = 0.5 mm, Mute input voltage 2 0.3 V at mute (active low) pin 7.
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.
4
PBL 385 71
16-pin BW DIP 16-pin BW SO
Figure 5. Pin configurations.
Pin Descriptions
Refer to figure 5.
Pin Name Function
1 +L Output of the transmitter amplifier. Connected to the line through a polarity guard diode bridge. 2 TO Output of the transmitter amplifier. Connected through a resistor of 47 to 100 ohm to -L,
sets the DC-resistance of the circuit. The output has a low ac. impedance and the signal is used
to drive a side tone balancing network. 3 TI Input of transmitter amplifier. Input impedance 17 kohm ± 20 %. 4,12
- L Negative power terminal, connected to the line through a polarity guard diode bridge.
5,13 6 +C Positive power supply terminal for most of the circuitry inside the PBL 385 71 (about 1 mA current
consumption). The +C pin should be connected to a decoupling capacitor of 47 µF to 150 µF. 7 Mute Mute input. Maximum voltage (to mute) is 0.3 V, current sink requirement of external driver is 100 µA. 8 GR Input for the gain regulation control circuitry. 9 MO Output of the microphone amplifier. 10 MI 1
Inputs of the microphone amplifier. Input impedance 1.7 kohm ± 20%. 11 MI 2
14 RI Input of receiver amplifier. Input impedance is 38 kohm ± 20 %. 15 RE 1
Receiver amplifier outputs. Output impedance approximately 3 ohms. 16 RE 2
}
}
+L
TO
TI
+C
GR
-L
1 2 3 4 5 6 7 8
14 13 12 11
9
10
RE 2 RE 1
-L
MO
-L
15
16
-L
Mute
M1
M2
RI
1 2
3 4 5 6 7 8
16 15
14 13
TO
+L
GR
-L
RE1
MI
TI
+C
RI
-L
MO
9
12
10
11
-L
RE2
Mute
MI
-L
}
5
PBL 385 71
Figure 7. Block connections.
Figure 6. AC-impedance.
Functional description
Design procedure; ref. to fig.4. The design is made easier through that all
settable parameters are returned to gro­und (-line), this feature differs it from bridge type solutions.To set the parameters in the following order will result in that the interaction between the same is minimized.
1. Set the circuit impedance to the line, either resistive (600) or complex. (R3 and C1). C1 should be big enough to give low impedance compared with R3 in the telephone speech frequency band.Too large C1 will make the start-up slow. See fig. 6.
2. Set the DC-characteristic that is required in the PTT specification or in case of a system telephone,in the PBX specification (R6).There are also internal circuit dependent requirements like supply voltages etc.
3. Set the attac point where the line length regulation is supposed to cut in (R1 and R2 in fig. 18). Note that in some countries the line length regulation is not allowed. In most cases the end result is better and more readily achieved by using the line length regulation (line loss compensation) than without. See fig. 13.
4.Set the transmitter gain and frequency response.
5. Set the receiver gain and frequency response. See text how to limit the max. swing to the earphone.
6. Adjust the side tone balancing network.
7. Set the RFI suppression components in case necessary. In two piece telephones the often ”helically” wound cord acts as an aerial. The microphone input with its high gain is especially sensitive.
8. Circuit protection. Apart from any other protection devices used in the de­sign, a good practice is to connect a 15V 1W zener diode across the circuit , from pin 1 to -Line.
Impedance to the line
The AC- impedance to the line is set by R3, C1 and C2. Fig.4. The circuits relatively high parallel impedance will not influence it to any noticeable extent. At low frequencies the influence of C1 can not be neglected. Series resistance of C1 that is dependent on the temperature and the quality of the component will cause some of the line signal to enter pin 6. This generates a closed loop in the transmitter amplifier that in it´s turn will create an active impedance thus lowering the impedance to the line. The impedance at high frequencies is set by C2 that also acts as a RFI suppressor.
In many specifications the impedance towards the line is specified as a complex network. See fig. 6. In case a). the error signal entering pin 6 is set by the ratio Rs/R19 (910), where in case b). the ratio at high frequencies will be Rs/ 220 because the 820 resistor is
bypassed by a capacitor. To help up this situation the complex network capacitor is connected directly to ground, case c). making the ratio Rs/220+820 and thus lessening the error signal. Conclusion: Connect like in case c) when complex impedance is specified.
DC - characteristic
The DC - characteristic that a telephone set has to fulfill is mainly given by the network administrator. Following parameters are useful to know when the DC behaviour of the telephone is to be set:
The voltage of the feeding system
The line feeding resistance 2 x.......
ohms.
The maximum current from the line at
zero line length.
The min. current at which the telephone
has to work (basic function).
The lowest and highest voltage
permissible across the telephone set.
The highest voltage that the
telephone may have at different line currents. Normally set by the network owners specification.The lowest voltage for the telephone is normally set by the voltages that are needed for the different parts of the telephone to function. For ex. for transmitter output amplifier, recei­ver output amplifier, dialler, speech switching.
1
2
+Line
R3
R6
PBL 38 571
+
3
C1
C2
-Line
Rs 1
How to connect a complex network. 220+820//Cx
Example:
a) b) c)
6
220
820
Cx
+
1
AM AT
AR
2
Transmitter summing input
Mute
+ Line
- Line
3
4
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