A switching regulator can provide an efficient means to deliver a well-regulated voltage for the GTM transceiver analog power supply. Unlike the linear regulator, the switching regulator does not depend on the voltage drop between the input voltage of the regulator and the output voltage to provide regulation. Therefore the switching regulator can supply large amounts of current to the load while maintaining high power efficiency. It is not uncommon for a switching regulator to maintain efficiencies of 95% or greater. This efficiency is not severely impacted by the voltage drop between the input of the regulator and the output. It is impacted by the load current in a much lesser degree than that of the linear regulator. Because of the efficiency of the switching regulator, the system does not need to supply as much power to the circuit, and it does not need to provide a means to dissipate power consumed by the regulator.
The disadvantages to the switching regulator are complexity of the circuit and noise generated by the regulator switching function. Switching regulator circuits are usually more complex than linear regulator circuits. This shortcoming in switching regulators has recently been addressed by several switching regulator component vendors. Normally, a switching power supply regulation circuit requires a switching transistor element, an inductor, and a capacitor. Depending on the required efficiency and load requirements, a switching regulator circuit might require external switching transistors and inductors. Besides the component count, these switching regulators require very careful placement and routing on the printed circuit board to be effective.
Switching regulators generate significant noise and therefore usually require additional filtering before the voltage is delivered to the GTM transceiver analog power supply input of the GTM transceiver. As the amplitude of the noise should be limited to less than 10 mVpp over the frequency range 10KHz to 80MHz, the power supply filter should be designed to attenuate the noise from the switching regulator to meet this requirement.