L9214A/G
Low-Cost Ringing SLIC
Preliminary Data Sheet
October 2001
halted to enable on-hook transmission. The ring trip
detector and common-mode current detector are active
during the ring mode. The user may adjust the crest
factor of the ring signal by selecting one of the two slew
rates. The two rates, high or low, allow the designer to
chose one set of external capacitors to meet the crest
factor range of 1.2 to 1.6 over a 3:1 frequency range by
software control alone. For increased power efficiency,
the crest factor should be kept as low as possible.
Description (continued)
Forward and reverse battery active modes are used for
off-hook conditions. Since this device is designed for
short- and medium-loop applications, the lower-voltage
VBAT2 is normally applied during the forward and
reverse active states. Battery reversal is quiet, without
breaking the ac path. The rate of battery reversal may
be ramped to control switching time.
With maximum VBAT1, the L9214 has sufficient power to
ring a 3 REN (2310 Ω + 24 µF) ringing load into 600 Ω
of physical wiring resistance. With maximum VBAT1, the
L9214 has sufficient power to ring a 2 REN (3500 Ω +
16 µF) ringing load into <1000 Ω of physical wiring
resistance. Loop ranges may be expanded by applying
a lower crest factor trapezoidal input waveform.
The magnitude of the overhead voltage in the forward
and reverse active modes allows for an undistorted sig-
nal of 3.17 dBm into 600 Ω. The ring trip detector is
turned off during active modes to conserve power.
On-hook transmission is not permitted in the scan
mode. In this mode, the tip ring voltage is derived from
the higher VBAT1 rather than VBAT2.
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.
In the scan and active modes, the overhead voltage is
set such that the tip/ring open loop voltage is 42.5 V
minimum for a primary battery of 63 V to 70 V for com-
patibility with maintenance termination units (MTUs).
Also, the maximum voltage with respect to ground
(tip or ring to ground) is 56.5 V to comply with UL™
1950/60950 ANNEX M.2 method B and IEC® 60950
(quiet interval of ringing). If the primary battery is below
–63 V, the magnitude of the tip/ring open circuit voltage
is approximately 17 V less than the battery.
Where PPM is required, it is injected into the audio
receive pins (ac-coupled). PPM shaping must be
done externally and the PPM level must be within the
1.12 Vrms (3.17 dBm, 600 Ω) level set by the amplifier
overhead in the active state.
Both the ring trip and loop closure supervision func-
tions are included. The loop closure has a fixed typical
10 mA on- to off-hook threshold in the active and scan
mode. In either case, there is a 2 mA hysteresis. The
ring trip detector requires a simple filter at the input.
The ring trip threshold internally at a given battery volt-
age is fixed, but the threshold can be adjusted through
an external voltage divider. Typical ring trip threshold is
20.1 mA for a –65 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.
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, the user, by use of the input states, performs
line reversals at the required frequency, which gener-
ates the power ringing signal. This signal may be
applied continuously but is normally cadenced to meet
country-specific requirements. The input states are
normally set to an active state when power ringing is
A common-mode current detector for tip or ring ground
detection is included for ground key applications. The
threshold is user programmable via external resistors.
See the Applications section of this data sheet for more
information on supervision functions.
Agere Systems Inc.
5
AGERE [ AGERE SYSTEMS ]
