CMX868 Low Power V.22bis Modem

This V.22bis modem is ideal for use in any telephone based information and telemetry system. Using V.22bis signalling, fast call set-up times and robust error-resistant transmission can be implemented by efficient low-power circuits.
The device uses low geometry CMOS techniques to provide multi-mode operation with very low power requirements.
The circuit can operate with full duplex operation at 2400/1200/300 b/s over 2 or 4 wire circuits.
Control of the device is via a simple high speed synchronous serial bus. This allows easy interfacing to a host μController. The data to be transmitted and received by the modem is also downloaded over the same high speed serial bus. This ensures a very efficient hardware implementation in systems with a host μController.
A V.22bis/V.22 compatible data randomiser and UART function is included in the device.
The integrated DTMF encoder/decoder can be used as part of the dial out function to enable the host μController to set up a data call easily. All 16 DTMF tone combinations are available along with encoder of a single tone melody mode.
A high current drive output is provided to drive an external off hook relay.
To allow simple line interfacing the device includes an on chip line hybrid driver.
The "answer", "originate" generators/detectors and call progress tone detectors included on the device make the set-up of the telephone call a simple matter for the host μController.
In many data collection and telemetry systems power consumption is of critical importance.
The device features a "Zero Power" standby mode. In this mode current consumption is typically 1μA. While in standby the device may be automatically activated by a ringing voltage or line voltage reversal input to the Ring/Line reversal detector. Once operating the device requires a minimum supply voltage of 2.7V and consumes 7mA typically.
The very low power requirement of the device makes it ideally suited to applications which draw their power supply from the telephone line itself.
On exiting from the "Zero power" standby mode the device will generate an interrupt signal. This can be used to wake the host μController allowing it to service the incoming data call.

For further information please contact kellyb@spectre-online.co.uk