FM1062 [ETC]
Low Voltage Transmission Circuit ; 低压输电线路\n
| 型号： | FM1062 |
| 厂家： | 
ETC |
| 描述： | Low Voltage Transmission Circuit
|
| 文件： | 总6页 (文件大小：104K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
Low voltage transmission circuits with dialler interface
FM1062 / FM1062A
1. GENERAL DESCRIPTION
The FM1062 and FM1062A are integrated circuits that perform all speech and line interface
functions required in fully electronic telephone sets. They perform electronic switching between
dialling and speech. The ICs operate at line voltage down to 1.6 V DC (with reduced performance)
to facilitate the use of more telephone sets connected in parallel. FM1062 / FM0162A improve the
EMC performance in-circuit which can enhance the telephone sets’ EMC.
2. FEATURES
• Low DC line voltage; operates down to 1.6 V (excluding polarity guard)
• Voltage regulator with adjustable static resistance
• Provides a supply for external circuits
• Symmetrical high-impedance inputs (64 κW) for dynamic, magnetic or piezoelectric microphones
• Asymmetrical high-impedance input (32 κW) for electret microphones
• DTMF signal input with confidence tone
• Mute input for pulse or DTMF dialling
– FM1062: active HIGH (MUTE)
– FM1062A: active LOW (MUTE)
• Receiving amplifier for dynamic, magnetic or piezoelectric earpieces
• Large gain setting ranges on microphone and earpiece amplifiers
• Line loss compensation (line current dependent) for microphone and earpiece amplifiers
• Gain control curve adaptable to exchange supply
• DC line voltage adjustment facility
• enhanced EMC performance
3. BLOCK DIAGRAM
Fig. 1 Block Diagram
ꢀ
4. Pin Configurations, Definitions
SYMBOL
LN
PIN
1
DESCRIPTION
positive line terminal
GAS1
2
gain adjustment; transmitting
amplifier
gain adjustment; transmitting
amplifier
non-inverting output; receiving
amplifier
gain adjustment; receiving
amplifier
ꢃ
ꢀ
ꢂ
ꢁ
5
6
7
8
ꢃꢄ
ꢃꢅ
ꢃꢁ
ꢃꢂ
12
11
ꢆꢇ
ꢊꢆꢍꢎ
ꢉꢈꢏ
GAS2
QR
3
4
5
ꢈꢉꢊꢃ
ꢈꢉꢊꢀ
ꢌꢎꢈ
ꢋꢌ
ꢈꢉꢌ
ꢐꢏꢏ
GAR
ꢑꢕꢓꢎ
6
7
8
9
inverting microphone input
non-inverting microphone input
NC
MIΧ−
MIC+
NC
VEE
IR
DTMF
MUTE
VCC
REG
AGC
SLPE
ꢑꢒꢏꢇ
ꢖꢓꢑꢗ
negative line terminal
ꢑꢒꢏꢍ
ꢊꢓꢉꢔ
10 ꢒꢌ
10 receiving amplifier input
11 dual-tone multi-frequency input
12 mute input (see note 1)
13 positive supply decoupling
14 voltage regulator decoupling
15 automatic gain control input
16 slope (DC resistance) adjustment
9
ꢐꢎꢎ
Note
Pin 12 is active HIGH (MUTE) for FM1062 and LOW (MUTE) for FM1062A.
5. ꢀꢁꢂꢃꢄꢅꢆꢂꢇꢈꢉꢊꢃꢋꢅꢌꢄꢅꢆꢂ
Supplies VCC , LN, SLPE, REG
Power for the IC and its peripheral circuits is usually obtained from the telephone line. The
supply voltage is derived from the line via a dropping resistor and regulated by the IC. The supply
voltage VCC may also be used to supply external circuits e.g. dialling and control circuits. Decoupling
of the supply voltage is performed by a capacitor between VCC and VEE . The internal voltage
regulator is decoupled by a capacitor between REG and VEE . The DC current flowing into the set is
determined by the exchange supply voltage Vexch , the feeding bridge resistance Rexch and the DC
resistance of the telephone line Rline .
At line currents below 9 mA the internal reference voltage is automatically adjusted to a lower
value (typically 1.6 V at 1 mA). This means that more sets can be operated in parallel with DC line
voltages (excluding the polarity guard) down to an absolute minimum voltage of 1.6 V. At line
currents below 9 mA the circuit has limited sending and receiving levels. The internal reference
voltage can be adjusted by means of an external resistor (RVA ). This resistor when connected
between LN and REG will decrease the internal reference voltage and when connected between
REG and SLPE will increase the internal reference voltage.
Microphone inputs MIC+ and MIC− and gain pins GAS1 and GAS2
The circuit has symmetrical microphone inputs. Its input impedance is 64 kΩ (2 x 32 kΩ) and
its voltage gain is typically 52 dB (when R7 = 68 kΩ, see Figures 2 and 3). Dynamic, magnetic,
piezoelectric or electret (with built-in FET source followers) can be used. The gain of the
microphone amplifier can be adjusted between 44 dB and 52 dB to suit the sensitivity of the
ꢁ
transducer in use. The gain is proportional to the value of R7 which is connected between GAS1
and GAS2.
Input MUTE (FM1062)
When MUTE is HIGH the DTMF input is enabled and the microphone and receiving amplifier
inputs are inhibited. The reverse is true when MUTE is LOW or open-circuit. MUTE switching
causes only negligible clicking on the line and earpiece output. If the number of parallel sets in use
causes a drop in line current to below 6 mA the speech amplifiers remain active independent to the
DC level applied to the MUTE input.
Input MUTE (FM1062A)
When MUTE is LOW or open-circuit, the DTMF input is enabled and the microphone and
receiving amplifier inputs are inhibited. The reverse is true when MUTE is HIGH. MUTE switching
causes only negligible clicking on the line and earpiece output. If the number of parallel sets in use
causes a drop in line current to below 6 mA the DTMF amplifier becomes active independent to the
DC level applied to the MUTE input.
Dual-tone multi-frequency input DTMF
When the DTMF input is enabled dialling tones may be sent on to the line. The voltage gain
from DTMF to LN is typically 25.5 dB (when R7 = 68 kΩ) and varies with R7 in the same way as the
microphone gain. The signalling tones can be heard in the earpiece at a low level (confidence tone).
Receiving amplifier IR, QR and GAR
The receiving amplifier has one input (IR) and a non-inverting output (QR). The IR to QR gain is
typically 31 dB (when R4 = 100 kΩ). It can be adjusted between 20 and 31 dB to match the
sensitivity of the transducer in use. The gain is set with the value of R4 which is connected between
GAR and QR. The overall receive gain, between LN and QR, is calculated by subtracting the anti-
sidetone network attenuation (32 dB) from the amplifier gain. The output voltage of the receiving
amplifier is specified for continuous-wave drive. The maximum output voltage will be higher under
speech conditions where the peak to RMS ratio is higher.
Automatic Gain Control input AGC
Automatic line loss compensation is achieved by connecting a resistor (R6) between AGC and
VEE . The automatic gain control varies the gain of the microphone amplifier and the receiving
amplifier in accordance with the DC line current. The control range is 5.8 dB which corresponds to a
line length of 5 km for a 0.5 mm diameter twisted-pair copper cable with a DC resistance of 176
Ω/km and average attenuation of 1.2 dB/km). Resistor R6 should be chosen in accordance with the
exchange supply voltage and its feeding bridge resistance. The ratio of start and stop currents of
the AGC curve is independent of the value of R6. If no automatic line-loss compensation is required
the AGC pin may be left open-circuit. The amplifiers, in this condition, will give their maximum
specified gain.
Enhanced EMC performance
The input pins FM1062 / FM1062A are added RC filters to improve the EMC performance, so
the telephone sets which used FM1062 / FM1062A are easily to handle the EMC design.
ꢂ
6. LIMITING VALUES
SYMBOL PARAMETER
VLN
CONDITIONS
MIN. MAX. UNIT
positive continuous line voltage
12
13.2
V
V
−
−
VLN(R)
repetitive line voltage during
switch-on or line interruption
repetitive peak line voltage for a
1 ms pulse per 5 s
VLN(RM)
28
V
R9 = 20 Ω; R10 = 13 Ω;
see Fig.6
−
Iline
Ptot
Tamb
Tstg
line current
total power dissipation
operating ambient temperature
storage temperature
140
ꢀꢁꢁ
+75
+125
mA
mW
oC
oC
R9 = 20 Ω
R9 = 20 Ω
−
−
−25
−40
7. CHARACTERISTICS
Iline = 11 to 140 mA; VEE = 0 V; f = 800 Hz; Tamb =25 oC; unless otherwise specified.
SYMBOL
VLN
PARAMETER
voltage drop over
CONDITIONS
MIC inputs open-circuit
MIN.
TYP. MAX. UNIT
circuit between LN Iline = 15 mA
Iline = 100 mA
3.55
4.9
4.0
5.7
V
V
4.25
6.5
ICC
VCC
supply current
supply voltage
available for
VCC = 2.8 V
Iline = 15 mA;
MUTE = HIGH Ip = 1.2 mA
1.35
mA
−
0.9
1.9
2.7
3.5
V
peripheral circuitry MUTE = HIGH Ip = 0 mA
MUTE = LOW Ip = 1.2 mA
2.5
2.2
3.4
2.7
3.8
4.5
V
V
MUTE = LOW Ip = 0 mA
2.5
3.4
3.8
V
Gv MIC
voltage gain MIC+
or MIC− to LN
voltage gain from
DTMF to LN
output voltage
(RMS value)
52.0
45.5
25.5
54.5
47.0
27.0
dB
dB
dB
Iline = 15 mA; R7 = 68 kΩ
Iline = 100 mA; R7 = 68 kΩ
Iline = 15 mA; R7 = 68 kΩ
50.5
44.0
24.0
Gv DTMF
VLN(rms)
Gv RA
THD = 10% Iline = 15 mA
1.7
2.3
V
−
voltage gain from
IR to QR
29.5]
24.5
31
26
32.5
27.5
dB
dB
Iline = 15 mA; RL = 300 Ω
Iline = 100 mA; RL = 300 Ω
Vo(rms)
output
voltage THD = 2%; sine wave drive;
(RMS value)
R4 = 100 kΩ; Iline =15 mA;
Ip =0 mA RL = 150 Ω
RL = 450 Ω
0.22
0.3
0.33
0.48
−
−
V
V
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8. APPLICATION CIRCUITS
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