e-stlc3095 STMicroelectronics, e-stlc3095 Datasheet - Page 15

• Manufacturer Part Number: e-stlc3095
• Description: Integrated Pots Interface For Home Gateway And Wll
• Manufacturer: STMicroelectronics

STLC3095
Figure 6.
By selecting the proper capacitor value it is possible to get different crest factor values.
The following table shows the crest factor values obtained with a 20Hz and 25Hz ring
frequency and with 1REN. These value are valid either with European or USA specification:
Table 9.
1. Distortion already less than 10%.
The ring trip detection is performed by sensing the variation of the AC line impedance from
on hook (relatively high) to off-hook (low). This particular ring trip method allows to operate
without DC offset superimposed on the ring signal. Therefore the maximum possible ring
level on the load is obtained, starting from a given negative battery.
It should be noted that such a method is optimized for operation on short loop applications
and may not operate properly in the presence of long loop applications (> 500Ω).
Once ring trip is detected, the DET output is activated (logic level low), at this point the card
controller or a simple logic circuit should stop the D2 toggling in order to effectively
disconnect the ring signal and then set the STLC3095 in the proper operating mode
(normally ACTIVE).
Ring level in presence of more telephone in parallel
As already mentioned above the maximum current that can be drawn from the Vpos supply
is controlled and limited via the external RSENSE.
This also limits the power available at the self generated negative battery.
If for any reason the ringer load is too low the self generated battery drops in order to keep
the power consumption to the fixed limit. Consequently, the ring voltage level is also
reduced.
In the typical Buck Boost configuration with R
limited to about 770mA, which corresponds to an average current of 600mA max. In this
condition the STLC3095 can drive up to 2REN with a ring frequency fr=25Hz
(1REN = 1800Ω + 1.0µF, European standard).
In Fly-Back configuration the value of R
USA standards.
CREV
TIP/RING typical ringing waveform
Crest factors
22nF
27nF
33nF
GND
VBAT
TIP
RING
CREST factor @20Hz
dV/dT set
by CREV
SENSE
2.5V typ.
2.5V typ.
1.25
1.33
1.2
SENSE
= 220mΩ matches both the European and
= 130mΩ the peak current from Vpos is
59V
typ.
CREST factor @25Hz
Functional description
Not significant
1.26
1.32
(1)
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