2.2.2 Typical 5V Triplexer Application with External Microcontroller

Figure 2-4 shows a typical vehicle side triplexer application circuit with an external host microcontroller running from a single 5V voltage regulator. The digital I/O pins are always part of the VS power domain, and therefore, set to 5V operation. All internal voltages are generated by the embedded power management circuitry. The DC-DC Converter is assembled and activated to supply the analog front end and the power amplifier to substantially reduce the required power in the 5V domain.

The ATA5835 is powered on when the host sets the PWRON pin PB4 to ‘high’. After the internal start-up procedure, the ATA5835 enters the IDLEMode, which is signaled to the host by a system ready event on PB6. The system is now ready for SPI communication with the host. The ATA5835 can also be EEPROM-configured to directly switch to RXMode, PollingMode or TXMode after start-up.

The RF antenna switch is assembled with three SAW filters for channel prefiltering in a high-end three-channel application. Together with the internal digital channel filter, this application provides excellent channel separation and robustness against interferences.

In a bidirectional application, the user has to ensure that the RF peak voltage on the pins, SPDT_ANTx and SPDT_TX, stays in the range between -0.3V and VS_PA + 0.3V.