BL1062A1 [BELLING]

Low voltage transmission circuits with dialer interface; 与拨号接口的低电压传输电路


型号：	BL1062A1
厂家：	BELLING
描述：	Low voltage transmission circuits with dialer interface 与拨号接口的低电压传输电路
文件：	总7页 (文件大小：253K)
中文：	中文翻译
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BL1062A1

Low voltage transmission circuits with dialer interface

1. GENERAL DESCRIPTION

The BL1062A1 is integrated circuits that perform all speech and line interface functions

required in fully electronic telephone sets. It performs 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. BL1062A1 improves the EMC performance

in-circuit that 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 Κ Ω ) for dynamic, magnetic or piezoelectric

microphones

ꢀ

Asymmetrical high-impedance input (32 ΚΩ) for electret microphones

DTMF signal input with confidence tone

Mute input for pulse or DTMF dialling, 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 performanc

3. BLOCK DIAGRAM

Fig. 1 Block Diagram

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BL1062A1

4. Pin Configurations, Definitions

SYMBOL

DESCRIPTION

positive line terminal

GAS1

gain adjustment; transmitting

amplifier

GAS2

gain adjustment; transmitting

amplifier

non-inverting output; receiving

amplifier

gain adjustment; receiving

amplifier

GAR

Inverting microphone input

non-inverting microphone input

MIΧ−

MIC+

Negative line terminal

10 Receiving amplifier input

DTMF

MUTE

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

REG

AGC

SLPE

5. Function Description

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 ^VCCmay 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.

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BL1062A1

Input MUTE

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 V^EE. 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 BL1062A1 is added RC filters to improve the EMC performance, so the

telephone sets which used BL1062A1 are easily to handle the EMC design.

LIMITING VALUES

SYMBOL

PARAMETER

CONDITIONS

MIN. MAX. UNIT

positive continuous line voltage

13.2

−

LN(R)

repetitive line voltage during

switch-on or line interruption

repetitive peak line voltage for

a 1 ms pulse per 5 s

LN(RM)

R9 = 20 Ω; R10 = 13 Ω;

see Fig.6

−

line

line current

total power dissipation

operating ambient temperature

storage temperature

140

600

+75

+125

^oC

R9 = 20 Ω

−

−25

−40

tot

amb

stg

^oC

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BL1062A1

6. CHARACTERISTICS

line = 11 to 140 mA; VEE = 0 V; f = 800 Hz; Tamb =25 ^oC; unless otherwise specified.

SYMBOL

PARAMETER

voltage drop over

circuit between LN

and VEE

CONDITIONS

MIC inputs open-circuit

line = 1 mA

line = 4 mA

line = 15 mA

line = 100 mA

line = 15 mA;

VA(LN to REG)=68KΩ

VA(LN to SLPE)=39KΩ

CC = 2.8 V

MIN.

TYP. MAX. UNIT

1.6

1.9

4.0

5.7

3.55

4.9

4.25

6.5

Voltage drop over

circuit bewteen LN

and VEE

supply current

supply voltage

available for

3.5

4.5

1.35

−

0.9

Iline = 15 mA;

MUTE = LOW I

= 1.2 mA

= 0 mA

2.2

2.5

2.7

3.4

4.5

3.8

peripheral circuitry MUTE = LOW I

|Zi|

Input impedance

between MIC- and

MIC+

Common mode

rejection ratio

voltage gain MIC+

or MIC− to LN

Between MIC- and MIC+

KΩ

CMRR

MIC

52.0

45.5

54.5

47.0

line = 15 mA; R7 = 68 kΩ

line = 100 mA; R7 = 68 kΩ

50.5

44.0

Gain variation with F=300 and 3400 Hz

frequency

△Gvf

±0.2

reference

800Hz

Gain variation with Without R6;Iline=50mA;

△GvT

±0.2

temperature

Tamb=－25 and +75℃

reference to 25℃

Input impedance

of DTMT

voltage gain from

DTMF to LN

|Zi|

20.7

25.5

±0.2

KΩ

DTMF

27.0

line = 15 mA; R7 = 68 kΩ

24.0

Gain variation with F=300 and 3400 Hz

frequency

△Gvf

reference

800Hz

Gain variation with Without R6;Iline=50mA;

△GvT

±0.2

temperature

reference to 25℃

output voltage

(RMS value)

Input impedence

of receiving

amb=－25 and +75℃

LN(rms)

THD = 10% line = 15 mA

1.7

2.3

−

|Zi|

KΩ

amplifier

voltage gain from

IR to QR

29.5

24.5

32.5

27.5

line = 15 mA; R

line = 100 mA; R

= 300 Ω

Gain variation with F=300 and 3400 Hz

frequency

△Gvf

±0.2

reference

800Hz

Gain variation with Without R6;Iline=50mA;

△GvT

±0.2

temperature

Tamb=－25 and +75℃

reference to 25℃

o(rms)

output

(RMS value)

voltage THD = 2%; sine wave drive;

R4 = 100 kΩ; I^line=15 mA;

=0 mA = 150 Ω

= 450 Ω

0.22

0.3

0.33

0.48

−

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BL1062A1

o(rms)

output

(RMS value)

voltage

THD = 10%; R4 = 100 kΩ;

line =15 mA; R = 150 Ω

MIC- or MIC+ to MUTE=Low

Voltage gain from

DTMT to QR

△G

-17

R4=100kΩ; R

MUTE=Low

R6=110kΩ

L=300Ω

Controlling

the

-5.8

gain from IR to QR

and the gain from

MIC+,MIC- to LN

gain control range

(bewteen AGC and VEE

line=70mA

)

lineH

Hightest

current

maximum gain

Lowest

line

for

lineL

line

for

current

maximum gain

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BL1062A1

Fig2 Test circuit for defining BL1062A1 voltage gain of MIC+, MIC- and DTMF inputs

Fig3 Test circuit for defining BL1062A1 voltage gain of receiving amplifier

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BL1062A1

7. APPLICATION CIRCUITS

Fig4 Typical application of BL1062A1

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BL1062A1 [BELLING]

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