Application information

TS4974

22/25

4.10

Notes on PSRR measurement

What is the 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 is the PSRR measured?

The PSRR is measured as shown in Figure 43.

Figure 43.

PSRR measurement

Principles of operation

●

●

●

No bypasss capacitor Cs is used

The PSRR value for each frequency is calculated as:

RMS is an rms selective measurement.

Cin1

330nF

Cin2

330nF

Cb

1µF

STBY control

Vcc

Vripple

8 Ohms

RL

10 Ohms

10 Ohms

S1

Volume DOWN

S2

Volume UP

470k

Rpd1

470k

Rpd1

470k

Rpu1

470k

Rpu2

VCC

VCC

DIGITAL VOLUME

CONTROL

BIAS

STBY

+

1

2

3

9

8

Vin-

Vin+

BYP ASS

STBY

Vout-

Vout+

U1

TS4974 DFN10

PSRR

20

Log

RMS

Output

()

RMS

Vripple

()

----------------------------------

×

dB

()

=