L9215A/G
Short-Loop Sine Wave Ringing SLIC
Data Sheet
September 2001
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.
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.
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.
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.
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.
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.
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.
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.
Agere Systems Inc.
5
AGERE [ AGERE SYSTEMS ]
