L3000N datasheet(8/32 Pages) STMICROELECTRONICS

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In the same condition the power dissipation of

L3092 is typically 100mW.

2) STAND-BY (SBY) MODE

In this mode the bias currents of both L3000N

and L3092 are reduced as only some parts of the

two circuits are completely active, control inter-

face and current sensors among them. The cur-

rent supplied to the line is limited at 10mA, and

the slope of the DC characteristic corresponds to

2 x RFS.

The AC characteristic in Stand-by corresponds to

a low impedance (2 x RP)

In Stand-by mode the line voltage polarity is just

in direct condition, that is the TIP wire more posi-

tive than the RING one as in Conversation Mode.

When the SLIC is in Stand-by mode, the power

dissipation

L3000N

does

not

exceed

120mW from – 48V) eventually increased of a

certain amount if some current is flowing into the

line.

The power dissipation of the L3092 in the same

condition is typically 50mW.

SBY Mode is usually selected when the tele-

phone is in on-hook. It allows a proper off-hook

detection also in presence of high common mode

line current or with telephone set sinking few mil-

liAmpere of line current in on hook condition.

3) POWER DOWN (PD) MODE

In this mode the L3000N present a high imped-

ance (> 1 Mohm) to the line and cannot feed any

line current.

The L3092 forces L3000N in Power Down discon-

necting its bias Resistor, RH, from the ground

through the output pin PD0.

The power dissipation from the battery volt-

age (– VB) is almost equal to zero and the power

dissipation of L3092 is typically 50mW.

The PD mode is normally used in emergency

condition but can be used also in normal on-hook

condition.

In this case the off-hook detection is performed

using the line sense comparator integrated in the

L3092.

The fig. 4 shows the functional circuit to perform

the off hook detection in Power down mode.

The resistor RR and RT feed the line current. The

voltage at the terminal of the resistor RS con-

nected to RING wire is normally – 48V.

When there is a loop resistor between TIP and

Figure 1: DC Characteristics in Conversation

Mode

Figure 2: Line Current versus Loop Resistance -

RFS = 200

Ω; Limiting Currents:

25/40/60mA

Figure 3: DC Characteristics in Stand-by Mode

L3000N - L3092

8/32

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