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LSD20463

SmartHCF™ Mobile Modem

Conexant Systems 

SmartHCF Mobile Modem Designer’s Guide

The SmartDAA Interface communicates with, and supplies power and clock to, the LSD through the DIB.

1.4.2 Digital Isolation Barrier (DIB) (OEM Supplied)

The DIB electrically DC isolates the HSD from the LSD and telephone line. The HSD is connected to a fixed digital ground

and operates with standard CMOS logic levels. The LSD is connected to a floating ground and can tolerate high voltage input

(compatible with telephone line and typical surge requirements).

The DIB power and clock transformer (PCXFMR) couples power and clock from the HSD to the LSD. (See Mobile Product

Updates for qualified transformers.)

The DIB data channel supports bidirectional half-duplex serial transfer of data, control, and status information between the

HSD and the LSD.

1.4.3 SmartDAA Line Side Device (LSD)

The LSD includes a Line Side DIB Interface (LSDI), a coder/decoder (codec), and a Telephone Line Interface (TLI).

The LSDI communicates with, and receives power and clock from, the SmartDAA interface in the HSD through the DIB.

LSD power is received from the DIB PCXFMR secondary winding through a half-wave rectifying diode and capacitive power

filter circuit. The CLK input is also accepted from the PCXFMR secondary winding through a capacitor and a resistor in

series.

Information is transferred between the LSD and the HSD through the DIB_P and DIB_N pins. These pins connect to the HSD

DIB_DATAP and DIB_DATAN pins, respectively, through the DIB.

The TLI integrates DAA and direct telephone line interface functions and connects directly to the line TIP and RING pins, as

well as to external line protection components.

Direct LSD connection to TIP and RING allows real-time measurement of telephone line parameters, such as the telephone

central office (CO) battery voltage, individual telephone line (copper wire) resistance, and allows dynamic regulation of the off-

hook TIP and RING voltage and total current drawn from the central office (CO). This allows the modem to maintain

compliance with U.S. and world-wide regulations and to actively control the DAA power dissipation.

1.4.4 Voice Codec (VC) (S Models)

The optional VC, packaged in a 32-pin TQFP, supports voice/full-duplex speakerphone (FDSP) operation with interfaces to a

microphone and speaker and to a telephone handset/headset.

100475A

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