Supply Allocation Exposure across Dual Sourced Low Tier Commercial Sensor Topologies
Dual sourcing low tier commercial sensors demands matching ASIC DSP group delays and thermal offset drift profiles to prevent host control loop instability.
Switched Capacitor AFE
Discrete Circuitry
Analog interface circuits use a network of switches and capacitors to sample voltages and perform mathematical operations without resistors. A switched capacitor afe provides a way to implement filters and gain stages on a small silicon area. This architecture is common in high resolution sensors due to its low power consumption.
It operates by moving packets of charge between capacitors at a high frequency.
Charge Transfer
The basic circuit mimics the behavior of a resistor by rapidly switching a capacitor between two nodes. The equivalent resistance is inversely proportional to the switching frequency and the capacitance. This allows for the creation of very high resistance values that would be impossible to fabricate with physical resistors.
Accuracy depends on the ratio of the capacitors rather than their absolute values.
Sampling Clock
A precise timing signal controls the opening and closing of the electronic switches. Jitter in this clock can introduce noise into the signal path. The switching frequency must be much higher than the highest signal frequency to avoid aliasing.
This clock signal is often generated by an internal oscillator.
Input Impedance
The switching action causes the input to look like a dynamic load. High impedance sensors may require a buffer to prevent signal distortion.