Si3016 Datasheet, PDF (15/48 Pages) List of Unclassifed Manufacturers – 3.3 V ENHANCED GLOBAL DIRECT ACCESS ARRANGEMENT

Si3016
current can be monitored via the LVCS bits. A significant
drop in loop current can signal a parallel handset going
off-hook. If a parallel handset causes the LVCS bits to
read all 0’s, the Drop-Out Detect (DOD) bit may be
checked to verify a valid line still exists.
When on-hook, the LVCS bits may also be read to
determine the line voltage. Significant drops in line
voltage may also be used to detect a parallel handset.
For the Si3016 to operate in parallel with another
handset, the parallel handset must have a sufficiently
high dc termination to support two off-hook DAAs on the
same line. The OFF bit in Register 16 is designed to
improve parallel handset operation by changing the dc
impedance from 50 Ω to 800 Ω and reducing the DCT
pin voltage.
Line Voltage/Loop Current Sensing
The Si3016 has the ability to measure both line voltage
and loop current. The five bit LVCS register reports line
voltage measurements when on-hook, loop current
measurements when off-hook, or on-hook line monitor
data depending on the state of the MODE, OH, and
ONHM bits. Using the LVCS bits, the user can
determine the following:
„ When on-hook, detect if a line is connected.
„ When on-hook, detect if a parallel phone is off-hook.
„ When off-hook, detect if a parallel phone goes on or
off-hook.
„ Detect if enough loop current is available to operate.
„ Detect if there is an overload condition which could
damage the DAA (see overload protection feature).
Line Voltage Measurement
The Si3016 reports the line voltage with the LVCS bits in
Register 19. LVCS has a full scale of 87 V with an LSB
of 2.75 V. The first code (0 → 1) is skewed such that a 0
indicates that the line voltage is < 3 V. The accuracy of
the LVCS bits is ±20%. The user can read these bits
directly through the LVCS register when on-hook and
the MODE bit is set to 1. A typical transfer function is
shown in Figure 8.
Loop Current Measurement
When the Si3016 is off-hook, the LVCS bits measure
loop current in 3 mA/bit resolution. These bits enable
the user to detect another phone going off-hook by
monitoring the dc loop current. The line voltage current
sense transfer function is shown in Figure 9 and is
detailed in Table 10.
30
25
20
LVCS
BITS
15
10
5
0
0 3 6 9 12 15 18 21 24 27 30 33 36 39 42 45 48 51 54 57 60 63 66 69 72 75 78 81 84 87
100
Loop Voltage (V)
Figure 8. Typical Loop Voltage LVCS Transfer Function
Rev. 0.44
15