MH88435-P データシートの表示（PDF） - Mitel Networks

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MH88435-P

Data Access Arrangement

Mitel Networks 

MH88435-P

Preliminary Information

30

25

20

(V(t-r)

15

10

5

Iloop=26mA

Iloop=20mA

Iloop=15mA

0

200

600

1000

1400

1800

2200

2600

3000

3400 3800

R2(kOhms)

Figure 3 - DC Programming Capabilities

Input Impedance

The MH88435 has a programmable input impedance

set by fitting external components between the ZA

pin and AGND.

For complex impedances the configuration shown in

Figure 4 is most commonly found.

ZA

R1

R2

Where the input impedance (Z) = 600R the equation

can be simplified to:

Zext = (10 x Z) - 1k3Ω

Zext = 4k7Ω

Note: A table of commonly used impedances can be

found in the DAA Application’s document MSAN-154.

Zext = external network connected between ZA and

AGND, Zint = 1.3kΩ (internal resistance).

C1

Figure 4 - Complex Impedances

To find the external programming components for

configuration 4, the following formula should be

used:

Zext = [(10 x R1)-1k3]+ [10 x R2)//(C1/10)]

e.g. If the required input impedance = 220Ω +

(820Ω//115nF), the external network to be connected

to ZA will be:

Zext = 900Ω + (8k2Ω//12nF)

Network Balance

The network balance impedance of the device can

be programmed by adding external components

between NB1 and NB2. For countries where the

balance impedance matches the line impedance, a

15kΩ resistor should be added between NB1 and

NB2.

Ringing Voltage Detection

The sensitivity of the ringing voltage detection

circuitry can be adjusted by applying an external

resistor between the RS and LOOP pins. With a

short circuit, the threshold sensitivity is ~10Vrms R7

can be calculated using the equation:

2-42

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