DS_1x22_017
73M1822/73M1922 Data Sheet
12.7 Voltage and Current Detection
The 73M1x22 is capable of detecting the following circumstances:
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Under voltage on the line
Over voltage on the line
Over current
These 73M1x22 built-in mechanisms provide protection to both the device itself and the external line
circuitry.
If enabled, Over Voltage and Over Current detection will cause the 73M1x22 to go on-hook without the
intervention of the host.
If configured in Line Powered mode, the detection of an Under-voltage condition causes the 73M1x22 to
switch automatically to Barrier Powered Operation (see Section 10.2.1). This is done without the
intervention of the host.
For each of the detection functions there are enable control and detection status. For each of the functions
there is a master detection function enable bit that is to be set in order for the functions to work.
12.8 Under Voltage Detection (UVD)
Under Voltage Detection is an important feature of 73M1x22. It is intended to determine if the phone line is
not capable of supplying the current that the 73M1x22 requires from the line for proper operation. If this
function is enabled and If the line is not capable of providing this current, the UVD condition will be asserted
and can become a source of interrupt from 73M1x22 to its connected host.
12.9 Over Voltage Detection (OVD)
If enabled, Over Voltage Detection is indicated if the device senses that the line voltage exceeds a defined
threshold. The device allows the selection of choice of either 60 Vpk or 70 Vpk (depending upon the
attenuation ratio, typically this is 100:1).
If enabled the 73M1x22 will automatically go on-hook if over voltage is detected.
12.10 AC Signal Over Load Detection
This is the same feature as used for the detection of billing tones (see Section 11.4). In this most generic
sense, this detector provides an indicator that the AC signal on the line exceeds a value of
3.5 Vpk.
12.11 Over Current Detection (OID)
When the line current exceeds the safe operating range of the 73M1x22 or the external transistors, the
device indicates this condition. If enabled, the 73M1x22 will automatically go on-hook if an over current
event is detected.
Rev. 1.6
71
TERIDIAN [ TERIDIAN SEMICONDUCTOR CORPORATION ]
