Knowledge Booster Training Bytes - Switched Capacitor and C2V Converter-Based Circuits

15 Aug 2023 • 4 minute read

In this Knowledge Booster blog, let us talk about the simulation of the circuits based on switched capacitors and capacitance-to-voltage (C2V) converters using various analyses available under the Shooting Newton method using the Spectre RF Option. The videos described in this blog are a part of the course: Spectre RF Analysis Using Shooting Newton Method.

We characterize the videos in this blog in two parts:

1. Switched capacitor-based circuits: These circuits consist of switching capacitors instead of physical resistors, which facilitates better matching due to reduced silicon area.

Video 1: What Are Switched Capacitor Circuits? (Video) (cadence.com) Here, a brief explanation about the switched capacitor circuits, along with the parameters and steps to simulate these using the Shooting Newton Engine, is given.
Video 2: Impact of maxacfreq and Sample Capacitance (csample) Parameters In pnoise Simulations For Switched-Capacitor Circuits (Video) (cadence.com) After a brief description of switched capacitor circuits, here you see the impact of two important parameters, maxacfreq and sample capacitance (csample) in the context of switched capacitor-based circuits:
- maxacfreq: This parameter is available in the periodic steady state (pss) Options and is set to ensure the calculation of accurate waveshape. It specifies the highest frequency used by SpectreRF in the subsequent small-signal analyses.
- Sample capacitance (csample): This parameter is specific to the simulation example used in this set of videos. For the switched capacitor-based circuits, it impacts the theoretical noise equivalent voltage.
Video 3: Performing the fullspectrum pnoise Analysis on a Sample-and-Hold Circuit For a Swept maxacfreq Parameter (Video) (cadence.com) Now, the fullspectrum periodic noise (pnoise) analysis is performed on a sample-and-hold circuit with the swept maxacfreq parameter, and its optimum value is determined (in the context of the circuit used here). This value is used for carrying out further measurements on this circuit.
Video 4: Performing the fullspectrum pnoise Analysis on a Sample-and-Hold Circuit For a Swept csample Parameter (Video) (cadence.com) Next, the value of maxacfreq obtained from the previous video is employed and the fullspectrum pnoise analysis is run on the sample-and-hold circuit with a swept sample capacitance (csample).
Video 5: Plotting the Transfer Function of a Third Order Switched-Capacitor Elliptic Filter Using pac Analysis (Video) (cadence.com) Here, the periodic AC (pac) analysis is run on a third-order switched-capacitor filter to plot its transfer function.
Video 6: Plotting the Output Sidebands of a Multi-Phase Switching Circuit Using pxf Analysis (Video) (cadence.com) Next, the periodic transfer function (pxf) analysis is performed for a multi-phase switching circuit and its output sidebands are plotted.

2. Capacitance-to-voltage (C2V) converter-based circuits: These are readout analog front-end circuits for capacitive MEMS sensors. These are mainly employed in microphone-related applications.

Video 7: What Are Capacitance-To-Voltage (C2V) Converters? (Video) (cadence.com) Here, a brief description of capacitance-to-voltage (C2V) Converters along-with various block present inside these is given.
Video 8: Performing Linear Range and Sensitivity Measurements Of a C2V Converter Using pss Analysis (Video) (cadence.com) Now, the linearity and sensitivity of the C2V Converter is measured by performing the Periodic Steady-State (pss) analysis.
Video 9: Performing the fullspectrum pnoise Analysis On a C2V Converter (Video) (cadence.com) Next, the fullspectrum pnoise analysis is run on a C2V Coverter circuit for plotting the output noise response and noise summary.
Video 10: Performing the pstb Analysis On The Amplifier Driven By the Capacitor Bridge (Video) (cadence.com) Here, the periodic stability (pstb) analysis is run on the amplifier driven by sensor capacitor bridge, both being initial blocks of the C2V converter circuit. Here, the simulation is done to plot the magnitude and phase of loop gain and finally the phase margin.

Want to Learn More?

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