73M1866B/73M1966B Data Sheet
DS_1x66B_001
An example of the use of the Seize state is for Australia, which requires this state for the first 300 ms
immediately after going off hook.
DCVI Performance
14
Australian
12
Prohibited Region
10
DCIV=xx
8
6
4
Australian Not Recommended Region
2
0
0
10
20
30
40
50
60
70
80
90
100
DC current, mA
Figure 35: Voltage versus Current in the Seize Mode is the Same for All DCIV Settings
To facilitate the quick capture of the loop, the bandwidth of the DC loop is high upon power up. On the
completion of DC loop capture, it should be lowered to avoid the interaction of DC and AC loops. See the
description of the ENNOM bit in Section 10.6.
10.2.1 Current Limit Detection
If the DAA Current Limiting feature is enabled and the device detects an I-limit condition, a status bit is set
to report this event.
10.3 AC Termination
The 73M1x66B supports 16 impedance configurations. This set of AC impedances has been selected to
provide global coverage without the need for changing external components.
The AC Termination function is controlled by an enable and a disable control bit and by writing the
appropriate network configuration code to the device. The AC Terminations provided include ones
suitable for ETSI ES 203 021-2, Australia, FCC and China, among others. See Section 10.7 on how to
select a configuration.
When using the 900 Ω termination, an additional gain of 1.75 dB should be added to the transmitter
path.
Upon selection of a particular AC impedance configuration, the 73M1x66B monitors the line and controls
the AC current back to the line, such that the desired impedance looking into the RXP pins is realized.
The 73M1x66B provides an AC transconductance circuit that is used to modulate the AC signal onto the
line as well as to regulate the current and provide the AC load in the AC signal path.
Figure 36 shows the magnitude response of the impedance matching filter for the case of ES 203 021-2.
66
Rev. 1.6
TERIDIAN [ TERIDIAN SEMICONDUCTOR CORPORATION ]
