7.13 THD + Noise

The total harmonic distortion (THD) of a signal is a measurement of the harmonic distortion, and is defined as

the ratio of the sum of the powers of all harmonic components to the power of the fundamental frequency at the

mux output. The on-resistance of the device varies with the amplitude of the input signal and results in distortion

when the drain pin is connected to a low-impedance load. Total harmonic distortion plus noise is denoted as

THD.

GND

S

D

Audio Precision

0.1 µF

0.1 µF

50

SxA / SxB / Dx

40

Figure 7-13. THD Measurement Setup

7.14 Power Supply Rejection Ratio (PSRR)

PSRR measures the ability of a device to prevent noise and spurious signals that appear on the supply voltage

pin from coupling to the output of the switch. The DC voltage on the device supply is modulated by a sine wave

of 620 mVPP. The ratio of the amplitude of signal on the output to the amplitude of the modulated signal is the

ACPSRR. A high ratio represents a high degree of tolerance to supply rail variation.

Figure 7-14 shows how the decoupling capacitors reduce high frequency noise on the supply pins. This helps

stabilize the supply and immediately filter as much of the supply noise as possible.

Network Analyzer

DC Bias

Injector

GND

S

D

0.1 µF

With & Without

Capacitor

SxA / SxB / Dx

50

Ω

50

Ω

50

Ω

0.1 µF

Figure 7-14. ACPSRR Measurement Setup

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TMUX6236

SCDS449 – APRIL 2022

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