14.6.4.1 Overview

While IEEE 802.15.4 is targeting low cost and low power applications, solutions supporting higher transmit output power are occasionally desirable. To simplify the control of an optional external RF front-end, a differential control pin pair can indicate that the AT86RF212B is currently in transmit mode.

The control of an external RF front-end is done via digital control pins DIG3/DIG4. The function of this pin pair is enabled with the PA_EXT_EN bit in the TRX_CTRL_1 register (TRX_CTRL_1.PA_EXT_EN). While the transmitter is turned off, pin 1 (DIG3) is set to low level and pin 2 (DIG4) to high level. If the radio transceiver starts to transmit, the two pins change the polarity. This differential pin pair can be used to control PA, LNA, and RF switches.

If the AT86RF212B is not in a receive or transmit state, it is recommended to disable the PA_EXT_EN bit to reduce the power consumption or avoid leakage current of external RF switches and other building blocks, especially during SLEEP state. If register bits PA_EXT_EN = 0, output pins DIG3/DIG4 are pulled-down to analog ground.