Fax Modems

The Silicon Labs Si2417 and Si2435 ISOmodem® devices are complete two-chip fax modems integrating our proprietary Direct Access Arrangement (DAA) to provide a globally-programmable telephone line interface with an unparalleled level of integration. Available in two small outline packages, these compact modem solutions eliminate the need for a separate DSP, modem controller, codec, isolation transformer, relays, opto-isolators, and a 2/4 wire hybrid. The Si2417 and Si2435 ISOmodems provide conventional fax formats with connect rates of up to 14,400 bps and 33,600 bps, over the Public Switched Telephone Network (PSTN). Other features include parallel phone detection, line-in-use monitoring, global caller ID, data/fax/voice discrimination, V.253 event reporting, and excellent surge immunity. 



  • AT command set
  • Fax protocols up to 33.6 kbps
  • DTMF generation and detection
  • General purpose tone detectors
  • Integrated DAA:
    • Over 6 kV surge immunity
    • On- and off- hook line voltage monitoring
    • Parallel phone (intrusion) detection
    • Over-current detection
  • Global Caller ID type 1 and type 2 decoding
  • Advanced voice signal processing (optional)
    • Acoustic Echo Cancellation
    • Line Echo Cancellation
    • Limiter for “Soft Clipping”
    • Programmable filtering and pre-emphasis
  • UART host interface
  • Low power; single 3.3 V supply
    • 20 mW in wake-on-ring or wake-on-polarity
    • 86 mW in normal operation
  • Firmware upgradeable
  • EEPROM interface
  • Lead-free, RoHS-compliant packages

Product Matrix

Part Number Max Fax Rate (bps) Line Side Device Host Interface Handset, TAM and Speakerphone Error Correction/Data Compression Package Type
14400 Si3018 UART; SPI No No TSSOP24
33600 Si3018 UART; SPI No No TSSOP24
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