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

Figure 18. The dynamic limiter function

Int. ref.0.855V

Line

30k

R10

Da

C5

7

RTC

R8

Db

Rectifier output

To gain regulation

Ref.

(1.16V)

10 GR

2.2k

+

C7

R14

R15

In ref.=0.855V

0V

Signal at GR without C7

DC 1

Figure 19. Transmitter output signal

limiter. See fig. 22 for data.

V

Amplitude limiter

16

VL

14

12

Amplitude limiter

10

ISR7

+

VTsat

(1x

1x

diode

Vce)

8

VTline 4Vp-p

6

4

2

IL

20

40

60

80

100

120

mA

Power down and input PD

During pulse dialling or register recall

(time controlled line break) the telephone

line is interrupted, hence the transmis-

sion and peripheral circuits are not

supplied during the breaks from the

line.The circuit has therefore an internal

power-down function that automatically

shuts down the current consuming parts

when the line voltage drops under a

certain level. This function reduces the

internal current consumption I+C

to≈120µA that in its turn minimizes the

charge up time of the capacitor C9 when

the line feed returns. The timing and pulse

shape at LD - dialling is improved. In

some cases the parameters around LD -

dialling can be improved by switching the

voltage at this input. Most of the modern

processors used for LD-dialling do also

supply a ”window” signal for the duration

of the LD-digit stream. This signal can be

used for the PD input. An improvement of

receiver and transmitter output swing at

very low line currents (IL<10mA) can be

achieved by controlling this PD input with

two resistors and a diode, maybe a

capacitor C1 is necessary, see fig. 21.

The circuit can be made to work down at

1.8V line voltage and 2.8mA line current.

Great care has to be taken to secure

against a possible latchup.

The PD input should not be held ”down”

at hook-on or at start to hook-off this

restricting the internal reference voltage

buid up and the circuit to ”wake up”. (It is

good practice to isolate the input with a

diode according to fig. 21, an open

collector drain can also be used). If the

adjusting feature with the two resistors is

used, it does not endanger the ”waking

up” process because the line voltage via

R19 will lift the level at PD input over the

critical reference voltage level of 1.16V. In

case this input is not used it should be left

”open”.

13

Share Link: