M2901CEM データシートの表示（PDF） - Teridian Semiconductor Corporation

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M2901CEM

V.22bis Single Chip Modem

Teridian Semiconductor Corporation 

DS_2901CE_031

73M2901CE Data Sheet

The transformer used for coupling will have an influence on the values of the components in the DAA

circuitry. The winding resistance, inductances and other characteristics of the transformer affect the

values of the impedance matching components. Make sure you have the transformer manufacturer’s

recommended circuit values when using other transformers. The values can be determined through

simulations, but may still require some adjustment to optimize the design.

6.2 73M2901CE Design Compatibility

The Teridian 73M2901CE is an enhanced version of the Teridian 73M2901CL and has a number of

additional features. These parts are highly compatible with the earlier 73M2901, however, users should

pay special attention when changing an existing 73M2901 design to use the 73M2901CE or 73M2901CL.

From a hardware standpoint, the key differences involve the User I/O pins USR10 and USR11, the

ASRCH pin and the HBDEN pin. An additional user I/O pin, USR20, replaces the ASRCH pin on the

73M2901CE. This pin may remain safely connected to TXD as long as the host software does not

reconfigure USR20 as an output (S104 bit0=0).

The 73M2901CE contains a high-efficiency, low-power hybrid driver. Due to this enhancement, HBDEN is no

longer required. This pin is an internal no-connect and can safely remain connected to its previous VPD or

GND. The functions of USR10 and USR11 are related to Caller ID and Line In Use/Parallel Pickup support.

Software enhancements to the 73M2901CE are typically achieved by the addition of new AT commands.

The device can be considered a superset of the 73M2901CL and 73M2901C. When converting a design to

the 73M2901CE, it is recommended that the user check the commands and register settings for backward

compatibility to the earlier parts (refer to the 73M2901CE AT Command User Guide for complete details).

6.3 Telephone Line Interface

Transmit levels at the line are dependent on the interface used between the pins and the line. The internal

hybrid line drivers eliminate the need for additional active circuitry to drive the line-coupling transformer.

The analog outputs TXAP and TXAN can be connected directly to the transformer (with the required

impedance matching series resistor or network). Depending upon transformer design (specifically dry

transformers), operation may be affected by the limited amount of DC current generated by the analog

outputs (DC offset). For this reason, Teridian recommends using a coupling capacitor with those

transformers to insure maximum performance.

The line interface circuits shown in Section 7 Reference Designs represent the basic components and

values for interfacing the Teridian 73M2901CE analog pins to the telephone line. The values of these

components have been calculated to minimize the transmission and reception path hybrid losses and are

linked by the following equation: R3 and R6 in Figure 3 and R15=0.242 x R13 in Figure 4.

Rev. 3.4

15

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