AG2120-S

Overview

The Ag2120 is a fully featured PSTN interface circuit available in DIL or SIL packages. It supports +5V and +3.3V supplies with loop current ranging from 14mA to 85mA. The device provides transformer isolation for high common-mode rejection, an on-board loop switch, and ringing detection sensitivity of 22V RMS at +5V or 14V RMS at +3.3V. It meets FCC Pt68 requirements and safety standards including EN 60950-1:2001 and UL60950-1:2003.

Feature Summary

• Integrated loop start protocol with optical loop switch control via LSC pin
• Programmable DC mask and line/network impedances for global market compatibility
• On-hook reception capability for Caller Line ID and telemetry applications
• Tip-ring polarity detection for reverse battery signaling

Applications

• PABX systems requiring trunk interfaces
• Long loop applications with high common mode interference
• Systems without ground connections
• Voice communication modules needing integrated protection

Procurement Notes

Verify package type (DIL or SIL) against design requirements. Confirm supply voltage selection (+5V or +3.3V) matches system architecture. Ensure external protection components meet specific regional regulatory standards such as FCC Pt68 or UL60950. Check DM pin resistor values for correct DC termination per target market.

Selection Notes

Select the Ag2120D for dual-in-line mounting or Ag2120S for single-in-line configurations. Consider impedance matching networks for specific line types like CTR21 or 600 Ohm. Evaluate protection needs for metallic surges and power cross events. Verify codec compatibility for audio signal interfacing via VIN and VOUT pins.

Part Context

The Ag2120 belongs to Silvertel's PSTN interface family, designed for robust telephone line connectivity. It integrates functions typically requiring multiple discrete components into a single module. This consolidation reduces board space and simplifies design for telecommunications equipment manufacturers.

Replacement Considerations

No direct public substitutes are documented. Designers should evaluate other Silvertel SLICs for similar feature sets if availability is constrained.

FAQ

How is the DC mask adjusted?

Connect a resistor between the DMa and DMb pins. For North America, Europe, and Far East markets, a 390K resistor is typically used.

What is the function of the F/R pin?

The Forward/Reverse pin indicates tip-ring polarity reversal. A logic 1 signifies reversed polarity, useful for detecting Caller Line ID or far-end answer signals.

Can the device operate without a ground connection?

Yes, the transformer isolation provides high common-mode rejection, making it suitable for un-grounded systems and long loop applications.