PBL3852 查看數據表（PDF） - Ericsson

零件编号

产品描述 (功能)

比赛名单

PBL3852

Universal Transmission Circuit

Ericsson  

PBL 3852

V

16

V telephone line

14

V line

V pin 4

12

10

8

V pin 2

6

4

V pin 8

2

V pin 9

IL

20

40

60

80

100

120

mA

Figure 8. DC-Characteristics. (R7 = 75 Ω)

Vcirc. = IPIN4 ⋅R19 + k1⋅ Vref + R7 ⋅Iline + k 2 ⋅ Vpin2 + a

( ) a = Ipin5 ⋅ 5. 5 ⋅103 if function DC − control at pin5 is used

k1⋅ Vref = 1.1V

k 2 ⋅ Vpin2 = 0. 5 ⋅R7 ⋅Iline

IPIN4 ≈ 1mA

The R7 will set the slope of the DC-char.

and the rest of the level is set by some

constants in the circuits as shown in the

equation. The slope of the DC-char. will

also influence the line length regulation

(when used) and thus the gain of both

transmitter and receiver. R7 acts also as

current protection for the circuit, must be

considered when low values are to be

used. The level of DC-characteristic can

be adjusted up at input pin 5 (some

100mV´s). The R21 adjusts a fix amount

where R20 couples the adjusted value to

line current. See fig. 32.

Microphone amplifier

The microphone amplifier in the PBL

3852 is divided into two stages. The first

stage is a true differential amplifier

providing high CMRR (-55 to -65 dB

typical) with voltage gain of 19 dB. This via a capacitor to the - input at pin 13.

stage is followed by a gain regulated

The DC supply resistors for the

amplifier with a regulation range from 6.5 microphone should be round 200Ω (in

dB to 14.5 dB, see fig. 15. The input of order not to overdrive the microphone

the microphone amplifier can be used for amplifier) and the feedback resistor (17k)

electret, magnetic or dynamic transducers is of that magnitude that it either

see fig. 9. The PBL 3852 has basically a influences the CMRR balance at the

higher gain regulation range (8 dB) than input or destroys the send mute by

the more or less standard 6 dB´s for gain bypassing signal round the microphone

regulation with line length, this in order to amplifier in mute state. For a dynamic

be able to be used in applications where microphone some more components are

”softclipping” is required. In case lower necessary, see fig. 10c. In order not to

regulation range is necessary, it is

influence the send mute the feedback

possible with some additional

signal is taken from transmitter output at

components.

pin 2 and because this signal is in

See reference figs. 4, 10c, 10f, 32 and opposite phase with the signal at pin 11,

33. For an electret microphone the

it is taken to the other input at pin 12. Also

circuitry will be simple, see fig. 10f. A

in order not to influence the DC-balance

resistor is added from the microphone of the microphone amplifier a capacitor

amplifier output, pin 11, to the positive has to be included in the feedback path

termination of the microphone and further and to maintain the CMRR of the

6

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