1.5.3 Typical 5V Application Circuit with External Microcontroller

The preceding figure shows a typical base station side application circuit with an external host μC running from a 5V voltage regulator. In contrast to the 3V application with external μC, directly connect the pin PB4 (PWRON) to VS; the ATA8510/15 enters the IDLEMode after power-on. In this configuration, the ATA8510/15 can work autonomously and the μC stays powered down to keep the current consumption low while remaining sensitive to RF telegrams.

To achieve a low current in IDLEMode, configure the ATA8510/15 in the EEPROM to work with the RC oscillators. Also, configure the ATA8510/15 for autonomous multi-channel and multi-application PollingMode. The external μC is notified by an event on pin 28 (EVENT) if an appropriate RF message is received. Until this event, the ATA8510/15 periodically switches to RXMode, checks the different services and channels configured in the EEPROM, and returns to power-down while the external host μC is still in Deep Sleep mode to keep the average current low. Upon valid RF message reception, the embedded receive buffer of the ATA8510/15 contains the message. After which, the transceiver can trigger a wake-up event for the external µC to retrieve this data for further processing.

In applications using the 2.4-5.5V supply (VS), it is important to note that only the ATA8510/15 ports PB0..PB7, PC0..PC5, and the external host μC use this supply. The power amplifier of the ATA8510/15 is limited to 3.6V; therefore, an internal LDO delivers a 2.2V or 3.0V supply voltage in TXMode on pin VS_PA. The capacitor on pin VS_PA is needed to stabilize this regulator and decouple the power amplifier supply voltage. The ports PC0..PC5 have internal 50-kΩ pull-up resistors and can be left open. The ANT_TUNE pin must be left open because the application example uses a non-loop antenna.

Independent of the type of application, match the RF_OUT and RF_IN to SPDT_TX and SPDT_RX by absorbing the parasitics of the SPDT switch into the matching network; hence, the SPDT_ANT is a 50Ω RX and TX port. Improve the harmonic suppression by using an optional filter on the antenna side.

For example, if the transmit path uses a SAW filter, the user must ensure that the RF peak voltage on the pins SPDT_ANT and SPDT_TX stays in the range between -0.3V and VS_PA + 0.3V. For more details, refer to RF Transmit Characteristics, parameters 12.45 and 12.50.