Application Information

TS4975

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4.6

Notes on PSRR measurement

What is PSRR?

The PSRR is the Power Supply Rejection Ratio. The PSRR of a device is the ratio between a

power supply disturbance and the result on the output. In other words, the PSRR is the ability of

a device to minimize the impact of power supply disturbance to the output.

How we measure the PSRR?

Figure 61. PSRR measurement schematic

Principles of operation

●

The DC voltage supply (Vcc) is fixed

●

The AC sinusoidal ripple voltage (Vripple) is fixed

●

No bypasss capacitor Cs is used

The PSRR value for each frequency is calculated as:

RMS is a rms selective measurement.

PSRR

20Log

RMS

Output

()

RMS

Vripple

()

---------------------------------- dB

()

=