LUCL8576BP-D AGERE [Agere Systems], LUCL8576BP-D Datasheet - Page 8

• Manufacturer Part Number: LUCL8576BP-D
• Description: Dual Ringing SLIC
• Manufacturer: AGERE [Agere Systems]

L8576B Dual Ringing SLIC
Functional Description
Transmit and Receive Interface
A second gain setting is provided to accommodate ring
trip. A switch is built into TG2. In ringing mode, TG1
and TG2 are internally connected, thus shorting out the
external gain resistor R
mit gain for ringing since ring trip is accomplished by
monitoring the voltage at DC
DC
higher currents of the ring trip.
The receive interface circuitry couples the differential
signal on receive inputs RCVP and RCVN to the
tip/ring drivers.
Data Interface
A 4-wire parallel interface (B2, RNGNG, NDISC, and
NSTAT) is provided for each channel to control signals
to and from the system controller. B2 controls the for-
ward/reverse battery in normal talk mode while
RNGNG enables the balanced ringing mode of opera-
tion, and NDISC performs a disconnect state. NSTAT
reflects either the loop detector output or the ring trip
detector output, depending on the mode of the section.
It is the responsibility of the system controller to recog-
nize ring trip detection and set RNGNG to a logic 0
state to terminate ringing. The system controller should
also use RNGNG to set ringing cadence.
Loop Current Detector
Each section of the device has an integral loop current
detector set at a nominal 12 mA of dc current. This is
used to detect off-hook transitions in the normal talk
state. When current less than the current threshold
(including no current) is flowing, NSTAT is at logic 1.
When loop current exceeds 12 mA, the output NSTAT
switches to a logic 0. No hysteresis is included.
8 8
OUT
at the appropriate level to accommodate the
GX1
. This provides a lower trans-
OUT
. This lower gain sets
(continued)
(continued)
Operating States
The L8576B device has four operating states:
Talk state—normal battery:
— Normal talk state.
— Battery feed is connected to the battery supply
— Both receive and transmit transmission paths are
— dc loop and instantaneous current limiters are
— NSTAT reflects the status of the switchhook
— PR is negative with respect to PT.
Talk state—reverse battery:
— Normal talk state.
— Battery feed is connected to the battery supply
— Both receive and transmit transmission paths are
— dc loop current limiter is powered up and active.
— NSTAT reflects the status of the switchhook
— PR is positive with respect to PT.
Ringing state:
— Normal ringing state.
— Both receive and transmit transmission paths are
— Balanced ringing is applied to PR and PT, in
— Current limiter is set for ringing limit.
— NSTAT reflects the status of the ring trip detector.
— Only one channel should be in this state at a time
Disconnect state:
— Tip and ring drive amplifiers are powered down.
— Pins PT and PR are high impedance (>100 k ).
— NSTAT is undefined.
— PT and PR voltage is undefined.
(V
powered up.
powered up and active.
detector.
(V
powered up.
detector.
inactive.
accordance with B2.
to control power dissipation.
BAT
BAT
).
).
Agere Systems Inc.
May 2001