L3000N datasheet(7/32 Pages) STMICROELECTRONICS

7 / 32 page

c) Ringing (RING)

d) Boost Battery (BB),(see Appendix B).

The fifth status, Power down (PD), is set by the

output pin PDO of the L3092 that disconnect the

Bias Resistor, RH, of L3000N from ground.

The main difference between Stand-by and

Power down is that in SBY the power consump-

tion on the voltage battery VB– (– 48V) is reduced

but the L3000N DC Feeding and monitoring cir-

cuits are still active, in PD the power consumption

on VB- is reduced to zero, and the L3000N is

completely switched off.

SLIC OPERATING MODES

Through the L3092 Digital Interface it is possible to

select six different SLIC OPERATING MODES :

1) Conversation or Active Mode (CVS)

2) Stand - By Mode (SBY)

3) Power - Down Mode (PD)

4) Automatic Stand - By Mode (ASBY)

5) Test Mode (TS)

6) Ringing Mode (RNG)

1) CONVERSATION (CVS) OR ACTIVE MODE

This operating mode is set by the control proces-

sor when the Off hook condition has been recog-

nized,

As far as the DC Characteristic is concerned two

different feeding conditions are present :

a) Current limiting region : the DC impedance of

the SLIC is very high (> 20K

Ω) and therefore the

system works like a current generator. By the

L3092 Digital Interface it is possible to selects the

value of the limiting current.:

60mA, 40mA or 25mA.

b) A standard resistive feeding mode : the charac-

teristic is equal to a battery voltage (VB-) minus

5V, in series with a resistor, whose value is set by

external components (see external component list

of L3092).

Switching between the two regions is automatic

without discontinuity, and depends on the loop re-

sistance. The SLIC AC characteristics are guar-

anteed in both regions.

Fig. 1 shows the DC characteristic in conversa-

tion mode.

Fig. 2 shows the line current versus loop resis-

tance for two different battery values and RFS =

200

Ω.

The allowed maximum loop resistance depends

on the values of the battery voltage (VB), on the

RFS and on the value of the longitudinal current

(IGDK). With a battery voltage of 48V, RFS = 200

Ω

and IGDK = 0mA, the maximum loop resistance is

over 3000

Ω and with IGDK = 20mA is about

2000

Ω (see Application Note on maximum loop

resistance for L3000N/L3092 SLIC KIT).

In conversation mode the AC impedance at the

line terminals is synthetized by the external com-

ponents ZAC and RP, according to the following

formula :

ZML =

ZAC

+ 2 ⋅ RP

Depending the characteristic of the ZAC network,

ZML can be either a pure resistance or a complex

impedance. This allows for ST SLIC to meet dif-

ferent standards as far as the return loss is con-

cerned. The capacitor CCOMP guarantees stabil-

ity to the system.

The two to four wire conversion is achieved by

means of a circuit that can be represented as a

Wheatstone bridge, the branches of which being:

1) The line impedance (Zline).

2) The SLIC impedance at line terminals (ZML).

3) The balancing network ZA connected between

RX input and ZB pin of L3092.

4) The network ZB between ZB pin and ground

that shall copy the line impedance.

It is important to underline that ZA and ZB are not

equal to ZML and to Zline. They both must be

multiplied by a factor in the range of 10 to 25, al-

lowing use of smaller capacitors.

In case the L3000N/L3092 kit is used with a second

generation

programmable

COMBO

(EG

TS5070FN) which is able to perform the two to four

wire conversion, the two impedances ZA and ZB

can be removed and the ZB pin connected to GND.

The -6dB Tx gain of the L3000N/L3092 SLIC kit in

fact allows to keep the echo signal always within

the COMBO Hybrid Balance Filter dynamic range.

In conversation mode, the L3000N dissipates

about 250mW for its own operation. The dissipa-

tion related to the current supplied to the line shall

be added, in order to get the total dissipation.

Table 1.

Pin 12 of L3092 Pin 12 of L3000N (C2)

–3

Pin 13 of L3092

Stand-by

Conversation

Not Used

(C1)

Not Used

B.B

Not Used

Pin 11 of L3000N

–3

Not Used

Ringing

Not Used

L3000N - L3092

7/32

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