Si3056
Si3018/19/10
5.22. Overload Detection
5.23. Gain Control
The Si3056 can be programmed to detect an overload The Si3056 supports different gain and attenuation
condition that exceeds the normal operating power settings depending on the line-side device being used.
range of the DAA circuit. To use the overload detection For both devices, gains of 0, 3, 6, 9, and 12 dB can be
feature, the following steps should be followed:
selected for the receive path with the ARX[2:0] bits. The
receive path can also be muted with the RXM bit.
Attenuations of 0, 3, 6, 9, and 12 dB can also be
selected for the transmit path with the ATX[2:0] bits. The
transmit path also can be muted with the TXM bit
(Register 15).
When using the Si3019 line-side device, the Si3056
provides even more flexible gain and attenuation
settings. The TXG2 and RXG2 bits (registers 38–39)
enable gain or attenuation in 1 dB increments up to
15 dB for the transmit and receive paths. The TGA2 and
RGA2 bits select either gain or attenuation for these
registers. The TXG3 and RXG3 bits (registers 40–41)
enable gain or attenuation in 0.1 dB increments up to
1.5 dB for the transmit and receive paths. The TGA3
and RGA3 bits select either gain or attenuation for these
registers. These additional gain/attenuation registers
are active only when the ARX[2:0] and ATX[2:0] bits are
set to all 0s.
1. Set the OH bit (Register 5, bit 0) to go off-hook, and
wait 25 ms to allow line transients to settle.
2. Enable overload detection by then setting the OPE
bit high (Register 17, bit 3).
If the DAA then senses an overload situation, it
automatically presents an 800 Ω impedance to the line
to reduce the hookswitch current. At this time, the DAA
also sets the OPD bit (Register 19, bit 0) to indicate that
an overload condition exists. The line current detector
within the DAA has a threshold that is dependant upon
the ILIM bit (Register 26). When ILIM = 0, the overload
detection threshold equals 160 mA. When ILIM = 1, the
overload detection threshold equals 60 mA. The OPE
bit should always be cleared before going off-hook.
DAC
ACT
TX
Analog
Hybrid
To
Link
CO
Si3056
ADC
Figure 24. Line-Side Device Signal Flow Diagram
IIRE
TXG3
TXG2
Digital
TXA2
SDI
TXA3
Filter
1 dB
Attenuation
Steps
1 dB
Gain
0.1 dB
Gain/ATT
Steps
Steps
To
Digital
Hybrid
Line-side
Device
Link
0.1 dB
1 dB
1 dB
Gain
Gain/ATT
Steps
Attenuation
Steps
Steps
IIRE
Digital
Filter
RXG3
RXA3
RXG2
RXA2
SDO
Figure 25. Si3056 Signal Flow Diagram
Rev. 1.05
35
SILICON [ SILICON ]
