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L9215A

Short-Loop Sine Wave Ringing SLIC

Agere -> LSI Corporation 

Data Sheet

September 2001

L9215A/G

Short-Loop Sine Wave Ringing SLIC

Description (continued)

Forward and reverse battery active modes are used for

off-hook conditions. Since this device is designed for

short-loop applications, the lower-voltage VBAT2 is

applied during the forward and reverse active states.

Battery reversal is quiet, without breaking the ac path.

Rate of battery reversal may be ramped to control

switching time.

The magnitude of the overhead voltage in the forward

and reverse active modes has a typical default value of

6.0 V, allowing for an undistorted signal of 3.14 dBm

into 900 Ω. This overhead can be increased to accom-

modate higher signal levels and/or PPM. The ring trip

detector is turned off during active modes to conserve

power.

Because on-hook transmission is not allowed in the

scan mode, an on-hook transmission mode is defined.

This mode is functionally similar to the active mode,

except the tip ring voltage is derived from the higher

VBAT1 rather than VBAT2.

In the on-hook transmission modes with a primary bat-

tery whose magnitude is greater than a nominal

51 V, the magnitude of the tip-to-ground and ring-to-

ground voltage is clamped at less than 56.5 V.

To minimize on-hook power, a low-power scan mode is

available. In this mode, all functions except off-hook

supervision are turned off to conserve power. On-hook

transmission is not allowed in the scan mode.

In the scan mode with a primary battery whose magni-

tude is greater than a nominal 51 V, the magnitude of

the tip-to-ground and ring-to-ground voltage is clamped

at less than 56.5 V.

A forward disconnect mode is provided, where all cir-

cuits are turned off and power is denied to the loop.

The device offers a ring mode, in which a power ring

signal is provided to the tip/ring pair. During the ring

mode, a user-supplied, low-voltage ring signal (ac cou-

pled) is input to the device’s RINGIN input. This signal is

amplified to produce the power ring signal. This signal

may be a sine wave or filtered square wave to produce

a sine wave on trapezoidal output. Ring trip detector

and common-mode current detector are active during

the ring mode.

This feature eliminates the need for a separate external

ring relay, associated external circuitry, and a bulk ring-

ing generator. See the Applications section of this data

sheet for more information.

PPM is injected at the PPMIN pin (ac coupled). This is a

high-impedance input that controls the PPM differential

voltage on tip and ring. The PPM signal may be

present at this pin at all times; however, PPM will only

be transmitted to tip and ring during a PPM active

mode. There are forward and reverse active, and for-

ward and reverse on-hook transmission modes with

PPM active.

No PPM shaping is done by the device. It is assumed

that a shaped PPM input is presented to PPMIN.

The maximum allowed PPM current at the 200 Ω ac

meter pulse load to avoid saturation of the device’s

internal AAC amplifier is 3 mArms. This signal level

is sufficient to provide a minimum 200 mVrms to the

200 Ω PPM load under maximum specified dc loop

conditions. Above 3 mArms PPM current, external

meter pulse rejection may be required. See the Appli-

cations section of this data sheet for more information if

on-hook transmission of PPM is required. Sufficient

overhead to accommodate on-hook transmission must

be programmed by the user at the OVH input.

Both the ring trip and loop closure supervision func-

tions are included. The loop closure has a fixed typical

10.5 mA on- to off-hook threshold in the active mode

and a fixed 11.5 mA on- to off-hook threshold from the

scan mode. In either case, there is a 2 mA hysteresis.

The ring trip detector requires only a single-pole filter at

the input, minimizing external components. The ring

trip threshold at a given battery voltage is fixed. Typical

ring trip threshold is 42.5 mA for a –75 V VBAT1.

Agere Systems Inc.

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