DESCRIPTION
The 73M1903C Analog Front End (AFE) IC includes fully differential hybrid driver outputs, which connect to the telephone line interface through a transformer-based DAA. The receive pins are also fully differential for maximum flexibility and performance. This arrangement allows for the design of a high performance hybrid circuit to improve signal to noise performance under low receive level conditions, and compatibility with any standard transformer intended for PSTN communications applications.
The device incorporates a programmable sample rate circuit to support soft modem and DSP based implementations of all speeds up to V.92 (56 kbps). The sampling rates supported are from 7.2 kHz to 16.0 kHz by programming the pre-scaler NCO and the PLL NCO.
The 73M1903C device incorporates a digital host interface that is compatible with the serial ports found on most commercially available DSPs and processors and exchanges both payload and control information with the host. This interface can be configured as a single master/slave mode or as a daisy chain mode that allows the user to connect up to eight 73M1903C devices to a single host for multi Analog Front End applications, such as, central server modems.
Costs saving features of the device include an input reference frequency circuit, which accepts a range of crystals from 4.9-27 MHz. It also accepts external reference clock values between 1 MHz and 40 MHz generated by the host processor. In most applications, this eliminates the need for a dedicated crystal oscillator and reduces the bill of materials (BOM).
The 73M1903C also supports two analog loop back and one digital loop back test modes.

FEATURES
• Two pairs of software selectable transmit differential outputs for worldwide impedance driver implementations.
• Up to 56 kbps (V.92) performance
• Programmable sample rates (7.2-16.0 kHz)
• Reference clock range of 1-40 MHz
• Crystal frequency range of 4.9-27 MHz
• Master or slave mode operation
• Daisy chain configurable synchronous serial Host interface
• Low power modes
• Fully differential receiver and transmitter
Drivers for transformer interface
• 3.0 V – 3.6 V operation
• 5 V tolerant I/O
• Industrial temperature range (-40 to +85 °C)
• JATE compliant transmit spectrum
• Package option: 32-pin QFN

APPLICATIONS
• Central site server modems
• Set Top Boxes
• Personal Video Recorders (PVR)
• Multifunction Peripherals (MFP)
• Fax Machines
• Internet Appliances
• Game Consoles
• Point of Sale Terminals
• Automatic Teller Machines
• Speaker Phones
• Digital Answering Machines
• RF Modems