UTCL6726

LINEAR INTEGRATED CIRCUIT

7

QW-R108-015,A

+

-

1.2V

15kΩ

15kΩ

+

0~470Ω

14

7

9

8

+

4.7~47μF

0~470Ω

+Line

1

Figure 5. DC regulator for external CMOS devices

APPLICATIONS INFORMATION

Refer to figure 6.

Gain regulation (R1, R2):

These resistors set the starting point for the gain-and side tone regulation.

Input impedance pin 6 is about 5.5 kΩ±20%.

Below are some typical values for R1 and R2, for some different supplies from telephone stations.

Battery feed

R1

R2

R6

No regulation

Set for short line gain.

All feedings

22kΩ

47~100Ω

Regulation:

48V, 2·200Ω

48V, 2·400Ω

36V, 2·500Ω

∞

∞

∞

∞

180kΩ

47Ω

75Ω

100Ω

Impedance to line (R3, C1, C2):

C1 in series with R3 and those in parallel with C2 give the impedance to the line from the set.

C2 must normally be there for the interference too.

The network is optimized with regard to the return loss.

The time constant R3, C1 cannot be allowed to be too small. If the time constant is to small, distortion at low

frequencies may be generated.

If R3 is changed this will change the DC-characteristic too, which set by the voltage at pin 4. The input current at pin

4 is about 1mA

Microphone selection (M1, R16):

The microphone can be either dynamic, magnetic or electrets. See figures 12,14 and 15.

The input impedance between pin 12 and 13 is about 1.7kΩ with typical variation ±20%

Transmitting gain and frequency response (R4, R5, C3, C4):

The network gives the amplification and frequency response for the transmitter. R5 is used when a greater

reduction of the gain is wanted. Input impedance at pin 3 is about 17 kΩ with typical variation ±20%.The sum of the