IA3223-C-FU Silicon Laboratories Inc, IA3223-C-FU Datasheet - Page 33

• Manufacturer Part Number: IA3223-C-FU
• Description: IC EZ DAA SYST SIDE WORLD 16QSOP
• Manufacturer: Silicon Laboratories Inc
• Series: EZ DAA™r

Specifications of IA3223-C-FU

• Function: Data Access Arrangement (DAA)
• Interface: Serial
• Number Of Circuits: 1
• Voltage - Supply: 3 V ~ 3.6 V
• Current - Supply: 7.9mA
• Power (watts): 2W
• Operating Temperature: -25°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 16-QSOP
• Includes: "911" Detection, Line-In-Use Detection, Parallel Pick-Up Detection, Ring Detection
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant, Lead free / RoHS Compliant

Line Drop
Line drop or wink is a complete drop in loop current from the Central Office switch, usually indicating call disconnect or call waiting
depending on the duration of the drop. Drops over 500 ms indicate disconnect while shorter drops indicate call waiting.
Consequently, it is important to time the duration of line drops with at least 10 ms resolution. Line drop is detected by the IA3223
System Side and flagged as the LD (Line Drop) status bit when the IA3222 Line Side receives insufficient loop current to keep it
operational (less than 10 mA).
Parallel Pickup
Generally, the primary reason for parallel-pickup detection is to allow automatic telephone devices (set-top box modems, fax
machines, etc.) to drop the line if a parallel telephone device attempts to dial. When a parallel telephone device goes off hook, the
loop current into the IA3222 Line Side decreases. The parallel-pickup circuit detects the low-frequency (less than 100Hz) transients
associated with a parallel pickup or hang up. To prevent spurious detects due to large, low frequency audio signals, the parallel-
pickup circuit attenuates audio-band signals. At the most sensitive setting, the parallel-pickup circuit will spuriously detect maximum
amplitude voice and DTMF signals but not modem signals. Parallel pickup dI/dt may be very low either because the parallel phone
has a high off hook voltage relative to Line Side IC or because the parallel phone holding circuit (electronic inductor) may turn on
slowly. The parallel-pickup circuit must therefore be very sensitive.
In a modem or fax application, lower parallel-pickup sensitivity can be set when dialing DTMF tones to prevent a spurious detection.
A higher sensitivity can then be set after dialing. Typically, a -10 dBm modem signal transmitted from the DAA will not trigger the
parallel-pickup detector on its most sensitive setting. One method for setting the levels is to raise the sensitivity until spurious
detects occur and then reducing the sensitivity by one step. Each step has about a 6dB difference in sensitivity.
Because the transmit-to-receive trans-hybrid return loss is poor at frequencies below 100 Hz, it is important that there be no low-
frequency transients in the transmitted audio signal, so as to prevent spurious parallel-pickup detections. Modem software can
create low-frequency settling transients when switching modes, typically during training or DTMF dialing. These may cause spurious
parallel-pickup detections. If adjusting the modem software is not possible, another solution is to put a low-frequency blocking
capacitor in the transmit path.
The LineStat Pin as Interrupt (Off Hook)
In the off-hook state, the LineStat pin behaves in a way similar to the on-hook state. The table below suggests criteria for qualifying
the interrupt when the DAA is off hook:
LSR required setting
High
Possible Cause of Interrupt
Line drop
Loop-current reversal
Parallel pickup
PPU bit high
Criterion
LD bit high
LP bit changed compared to before interrupt
IA3222/IA3223
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