ST75C52

·Transmission
 The hybrid will use the differential output TXA1 and TXA2 of the ST75C52/520.
  The nominal output level for each tone and each carrier must be equal to 0dBm when no attenuation is selected in the ST75C52/520 (default setting of the ST75C52/520).
· Reception
  The hybrid will only use the RXA1 input of the ST75C52/520 rather than RXA1 and RXA2 differential inputs in the basic hybrid.
  The far end carrier (modem signal) can be received between -1dBm and -44dBm.
· Power Supply
  Uses only one +12V power supply.

The ST75C52/520 uses basically a hybrid interface which allows to receive a V.17 signal between 0dBm and -45dBm with very good performances (see test report of the ST75C52/520). Such hybrid interface is perfect for high end equipment. The drawback is that the user has to use 4 operationnal amplifiers rather than 3 usally. As some manufactuers need to reduce the cost of their design we are going to introduce in this application note a simpler hybrid circuit which will save cost but also provide high performances.