CMOS RF Switch Control Without Charge Pumps or Capacitors
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Solution Overview
Problem
Conventional RF switch circuits for mobile devices face challenges in achieving high performance and low cost due to the need for charge pumps, which result in power loss and voltage spurs, and the addition of capacitors increases size and slows switching speed, while weakly biased MOSFETs do not provide competitive performance.
Innovation Solution
A CMOS-compatible RF switch circuit with a high voltage control circuit (HVCC) that uses standard CMOS logic circuits to supply high and low voltage signals to MOSFET switches, eliminating the need for charge pumps and capacitors by employing a medial voltage between the power supply and reference voltage to fully turn on and off the switches.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If charge pumps are used to provide high voltage signals to MOSFET switches, then the switches can be fully turned on and off, but power loss and voltage spurs occur
Solution Approach 1:
The patent extracts and removes the charge pump circuit from the RF switch design, replacing it with a voltage controller that generates appropriate gate voltages using standard CMOS circuits. This eliminates the source of power loss and voltage spurs while maintaining the necessary switch control functionality.
Solution Approach 2:
The patent replaces the charge pump mechanism with an electric field-based voltage control mechanism. The voltage controller uses electric fields to directly control the MOSFET gate voltages, substituting the mechanical charge pumping process with a more efficient electric field control approach that avoids power loss and voltage spurs.
2Reliability
If capacitors are added to provide voltage signals, then MOSFET switches can be controlled, but die size increases and switching speed decreases
Solution Approach 1:
The patent removes the capacitor-based voltage signal provision mechanism and replaces it with a voltage controller that directly generates the necessary gate voltages. This extraction eliminates the capacitive charging/discharging delays that limit switching speed while maintaining effective switch control.
Solution Approach 2:
The voltage controller performs preliminary action by pre-generating the appropriate high and low voltage signals needed for MOSFET control before the switching operation. This eliminates the need for capacitors to charge and discharge during switching, thereby maintaining fast switching speed while ensuring proper turn-on and turn-off states.
3Ease of manufacture
If standard CMOS circuits are used to control MOSFET switches, then cost is reduced and die size is minimized, but achieving full turn-on and turn-off becomes difficult
Solution Approach 1:
The patent applies parameter changes by modifying the voltage controller to generate gate voltages with amplitudes that exceed the MOSFET threshold voltage. By adjusting the voltage parameters (generating voltages greater than Vth), the system achieves full turn-on and turn-off of MOSFETs using standard CMOS circuits, thereby maintaining both cost-effectiveness and reliable switch performance.
Data Source
AI summary
A complementary metal-oxide semiconductor (CMOS) compatible radio frequency (RF) switch circuit and high voltage control circuit (HVCC) are disclosed. In a mobile device, an RF switch circuit couples a first RF circuit to a shared antenna through a low resistance path while electrically isolating other RF circuits from the antenna by a high resistance path. Each path in the RF switch circuit includes a series metal-oxide semiconductor (MOS) Field-Effect Transistor (FET) MOSFET switch which provides a low resistance path when fully turned on by a strong positive gate-to-source voltage and a corresponding body bias voltage, and a high resistance path when fully turned off by a strong negative gate-to-source voltage and corresponding body bias voltage. The RF switch circuit paths are controlled by a CMOS compatible HVCC which supplies high and low voltage signals to the gate node and body bias node of each MOSFET in each path.