L9313 datasheet(28/40 Pages) AGERE

28 / 40 page

Data Sheet

September 2001

Full-Feature SLIC and Ringing Relay for TR-57 Applications

L9313 Line Interface and Line Access Circuit

Agere Systems Inc.

Applications (continued)

dc Characteristics (continued)

Battery Feed (continued)

As illustrated in Figure 12, as loop length decreases,

the tip to ground voltage will decrease with a slope cor-

responding to one-half the internal dc feed resistance

of the SLIC (typical 75

Ω). The ring to ground voltage

will also decrease with a slope corresponding to one-

half the internal dc feed resistance of the SLIC, until the

SLIC reaches the current-limit region of operation. At

that point, the slope of the ring to ground voltage will

increase to the sum of one half the internal dc feed

resistance plus approximately 10 k

Ω.

The dc feed characteristic can be described by:

ILOOP =

VT/R =

where:

ILOOP = dc loop current.

VT/R = dc loop voltage.

VBAT = battery voltage magnitude.

VOH = overhead voltage.

RLOOP = loop resistance, including wire and handset

resistance.

RP = protection resistance.

Rdc = SLIC internal dc feed resistance.

12-3050.g (F)

Notes:

VBAT1 = –48 V.

VBAT2 = –24 V.

ILIM = 40 mA (RPROG = 66.5 k

Ω).

Figure 13. L9313 Loop Current vs. Loop Voltage

Refer to Figure 12 and Figure 13 in this section and to Fig-

ure 11 in the Automatic Battery Switch section.

Starting from the on-hook condition and going through

to a short circuit, the curve passes through two regions:

Region 1: on-hook and low loop currents: the slope cor-

responds to the dc feed resistance of the SLIC (plus

any series resistance). The open-circuit voltage is the

battery voltage less the overhead voltage of the device.

Region 2: current limit: the dc current is limited to a

value determined by VPROG. This region of the dc tem-

plate has a high resistance (10 k

Ω).

Notice that the I-V curve is uninterrupted when the

power is shifted from the high-voltage battery to the

low-voltage battery (if auxiliary battery option is used).

This is shown in Figure 11 in the Automatic Battery

Switch section.

Battery Reversal Rate

The rate of battery reverse is controlled or ramped by

capacitors FB1 and FB2. A chart showing FB1/FB2 val-

ues versus typical ramp time is given below. Leave

FB1 and FB2 open if it is not desired to ramp the rate of

battery reversal.

Table 15. FB1/FB2 Values vs. Typical

Ramp Time

* Typical recommended value for CFB1 and CFB2 is less

than 0.033

µF.

Longitudinal to Metallic Balance

Longitudinal to metallic balance at PT/PR is specified in

the Electrical Characteristics section of this data sheet.

VBAT

VOH

–

RLOOP

2RP

Rdc

------------------------------------------------------

VBAT

VOH

–

() RLOOP

•

RLOOP

2RP

Rdc

----------------------------------------------------------------

510

LOOP VOLTAGE (V)

Rdc

10 k

Ω

CFB1/CFB2*

Transition Time

0.01

µF

20 ms

0.1

µF

220 ms

0.22

µF

440 ms

0.47

µF

900 ms

1.0

µF1.8 s

1.22

µF2.25 s

1.3

µF2.5 s

1.4

µF2.7 s

1.6

µF3.2 s

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