2.5 Photo-Diode (PD) Output Behavior
Output from the PD pin provides a minimum of 0.2 mA
of photo-diode drive current for the opto-coupler LED
anytime sealing current exceeds 1 mA.
Because LED current is interrupted whenever loop
current is interrupted, the opto-coupler provides an
excellent means of indicating loop availability for
designs with a sealing current requirement.
2.6 On-State Behavior
2.6.1 Typical Conditions
On-state sealing current levels are determined by the
network’s power feed circuit and the loop’s dc
impedance. To compensate for low loop resistance or
very high loop voltage, the CPC1465 limits the
maximum sealing current to 70 mA.
The CPC1465 manages package power dissipation
by shunting excess sealing current through the 2.2 kΩ
4W power resistor located between the PR+ and PR-
pins.
2.6.2 Over-Voltage Conditions
Potentials in excess of 100 V applied to the tip and
ring interface will cause the CPC1465 to disable the
sealing current hold circuit and enter a standby state
with very little current draw. Once the over-voltage
condition is removed, the CPC1465 automatically
resumes normal operation.
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