stlc3040 STMicroelectronics, stlc3040 Datasheet - Page 8

• Manufacturer Part Number: stlc3040
• Description: Subscriber Line Interface Codec Filter, Cofislic
• Manufacturer: STMicroelectronics

STLC3040
4.3.2 - ACTIVE
This operating mode is selected by the card proc-
essor after an Off-Hook detection in order to allow
signal transmission on the line. Both Off-Hook
and ground-key detectors are operating.
GCI Command - Indicate channel and CR1 regis-
ter configuration (programmed by GCI Monitor)
defining Active modes are herebelow shown:
Table 5:
(*) This condition refers to STLC3040 only. If CR1.3 and CR1.2 are
equal (either 0 or 1) both STLC3040 and HV (L3000N, L3000S,
STLC3170) are in Active State. If CR1.3 and CR1.2 are different, one
of two line wires will be set in high impedance, while the STLC3040
will still be in Active mode.
Current Limit and Off-Hook threshold are pro-
grammable by CR6 register. If the fifth bit of the
Command-Indicate channel is set to 1 the Teletax
Signal is superimposed to the voice signal.
4.3.2.1 - DC feeding
As far as DC characteristic is concerned, SLIC is
basically working as a constant current device. It
turns automatically into a resistive feeding when
the programmed current limitation value cannot
be held due to high line resistance. In active
mode the constant current value is programmable
Figure 6: TTX Shaping
8/49
SLIC MODE
ACTIVE
ACTIVE + TTX
TIM
V
V
V
S
SS
S
C/I
(7)
0
0
2 CR10 LSB
PROGRAMMED VOLTAGE AS PROG IN CR10
C/I
(6)
1
1
C/I
(5)
0
1
CR1
(7)
X
X
(*)CR1
1/0
1/0
(3)
(*)CR1
1/0
1/0
(2)
in 1.1mA steps ranging from 0mA to 69.3mA. In
resistive feeding region SLIC kit operates like a
constant voltage source with a series impedance
Rfeed = 2Rp+n 2 50
protection resistor and n a value set from 1 to 8
via CR8 register).
Voltage drop (Fig. 4) can be programmed in order
to optimize voltage feeding characteristic, accord-
ing to AC signal swing requested (ex: voice, voice
+ 2Vrms TTX, voice + 5Vrms TTX):
Vd3000 = drop due to internal HV (L3000N,
L3000S, STLC3170) architecture
VdAC = AC headroom on Vout (170mV typ.)
VdTTX = TTX headroom on Vout (from 0 to 465mV
(15x31) typ. depending on programmed TTX level).
At HV (L3000N, L3000S, STLC3170) two wires
the following equation must be used:
V
4.3.2.2 - Metering Generation
TTX signal is internally generated, filtered and
shaped. Shaping is carried out by a gradual in-
crease of metering pulse level of a level step (see
CR10 register) per signal half period (please see
Fig. 6). TTX can be programmed both in fre-
quency (12 or 16 KHz ) and open loop amplitude
(from 0 to 10Vrms in 255 steps). The output im-
pedance at TTX frequency is just 2 x R
fore the proper value should consider the drops
DROP(TIP/RING)
V
SS
V
DROP
(2.8V typ.)
= Vd3000 + 40 (VdAC + VdTTX)
= 9.6V + CR10 [7..3] 15mV 40.
(being Rp the external
D96TL265A
p
; there-