2 Application

Figure 2-1 shows an example application of the AMC7924 and TMUX6234. The 24 DACs, DAC banks with different output voltages, and wide supply range of the TMUX6234 allow for multiple circuit implementations. In the application, the first two switches supply negative voltage for GaN PAs, and the last two switches supply positive voltage for LDMOS PAs.

The first switch shows DAC_A0 providing the GaN on voltage, and DAC_A1 providing the pinch-off voltage. The second switch shows the pinch-off voltage being provided by the negative supply. The third switch shows DAC_B0 providing the LDMOS on voltage, and DAC_B1 providing the pinch-off voltage. The last switch shows the pinch-off voltage being provided by ground.

The fast switching of the TMUX6234 allows for the PA to turn off quickly when not being used. This stops PA from drawing current and thus saves significant system power. This functionality is also desirable in wireless infrastructure that implements time division duplex. Fast switching allows for less downtime where the antenna cannot receive or transmit information, thus improving system functionality and efficiency.

In addition, the 24 ADCs can be used to monitor the output voltages, the input supplies, and GaN and LDMOS current with the use of a current shunt monitor (CSM). All 24 ADCs have user-programmable high and low limits that can trigger alarms in the device. Furthermore, the AMC7924 has a dedicated GPIO pin that can function as an ALARMOUT indicator, giving the host a signal when the AMC has detected an alarm condition. Figure 2-2 shows some examples of possible monitor circuits.