HC55151 datasheet(13/35 Pages) INTERSIL

13 / 35 page

4-13

23. Four-Wire to Two-Wire Gain Tracking - The 4-wire to 2-wire

gain tracking is referenced to measurements taken for

ERX = -10dBm, 1.0kHz signal, EG source removed from circuit,

RL = 600Ω and is computed using the following equation:

G4-2 = 20 • log (VTR/ERX) vary amplitude -40dBm to +3dBm,

or -55dBm to -40dBm and compare to -10dBm reading.

VTR, RL and ERX are defined in Figure 8. The level is specified at

the 4-wire receive port and referenced to a 600

Ω impedance level.

24. Two-Wire Idle Channel Noise - The 2-wire idle channel noise

at VTR is specified with the 2-wire port terminated in 600Ω (RL)

and with the 4-wire receive port (VTX) floating (Reference

Figure 9).

25. Four-Wire Idle Channel Noise - The 4-wire idle channel noise

at VTX is speciﬁed with the 2-wire port terminated in 600Ω (RL).

The noise specification is with respect to a 600

Ω impedance

level at VTX. The 4-wire receive port (VTX) floating (Reference

Figure 9).

26. Harmonic Distortion (2-Wire to 4-Wire) - The harmonic

distortion is measured within the voice band with the following

conditions. EG = 0dBm at 1kHz, RL = 600Ω. Measurement

taken at VTX. (Reference Figure 7).

27. Harmonic Distortion (4-Wire to 2-Wire) - The harmonic

distortion is measured within the voice band with the following

conditions. ERX = 0dBm0. Vary frequency between 300Hz and

3.4kHz, RL = 600Ω. Measurement taken at VTR. (Reference

Figure 8).

28. Constant Loop Current - The constant loop current is

calculated using the following equation:

IL = 1000/RLIM = VTR/600 (Reference Figure 10).

29. Ground Key Detector - (TRIGGER) Ground the Ring pin

through a 2.5k

Ω resistor and verify that GKD goes low.

(RESET) Disconnect the Ring pin and verify that GKD goes

high.

(Hysteresis) Compare difference between trigger and reset.

30. Electrical Test - Not tested in production at -40oC.

Circuit Operation and Design Information

The UniSLIC14 family of SLICs are voltage feed current

sense Subscriber Line Interface Circuits (SLIC). For short

loop applications, the voltage between the tip and ring

terminals varies to maintain a constant loop current. For long

loop applications, the voltage between the tip and ring

terminals are relatively constant and the loop current varies

in proportion to the load.

The tip and ring voltages for various loop resistances are

shown in Figure 13. The tip voltage remains relatively

constant as the ring voltage moves to limit the loop current

for short loops.

The loop current for various loop resistances are shown in

Figure 14. For short loops, the loop current is limited to the

programmed current limit, set by RILIM. For long loop

applications, the loop current varies in accordance with

Ohms law for the given tip to ring voltage and the loop

resistance.

The following discussion separates the SLIC’s operation into

its DC and AC paths, then follows up with additional circuit

and design information.

DC Feed Curve

The DC feed curve for the UniSLIC14 family is user

programmable. The user deﬁnes the on hook and off hook

overhead voltages (including the overhead voltage for off

hook pulse metering if applicable), the maximum and

minimum loop current limits, the switch hook detect

threshold and the battery voltage. From these requirements,

the DC feed curve is customized for optimum operation in

any given application. An Excel spread sheet to calculate the

external components can be downloaded off our web site

www.intersil.com/telecom/unislic14.xls.

FIGURE 13. TIP AND RING VOLTAGES vs LOOP RESISTANCE

LOOP RESISTANCE (

Ω)

-5

-10

-15

-20

-25

-30

-35

-50

-40

-45

200

600

1000 1400 1800 2000

10K

CONSTANT

LOOP CURRENT

REGION

VBH = -48V

RD = 41.2k

Ω

ROH = 38.3k

Ω

RDC_RAC = 19.6k

Ω

RILim = 33.2k

Ω

CONSTANT TIP TO RING

VOLTAGE REGION

-44.5V

-2.5V

TIP

RING

FIGURE 14. LOOP CURRENT vs LOOP RESISTANCE

LOOP RESISTANCE (

Ω)

200

600

1.4K 1.8K

2.2K 2.6K

3.8K

3.0K 3.4K

CONSTANT

LOOP CURRENT

REGION

VBH = -48V

RD = 41.2k

Ω

ROH = 38.3k

Ω

RDC_RAC = 19.6k

Ω

RILim = 33.2k

Ω

CONSTANT TIP TO RING

VOLTAGE REGION

HC55120, HC55121, HC55130, HC55131, HC55140, HC55141, HC55142, HC55143, HC55150, HC55151

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