Application information

TS4998

28/33

4.13

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 68.

Figure 68.

PSRR measurement

Principles of operation

●

●

●

The PSRR value for each frequency is calculated as:

RMS is an rms selective measurement.

Cin1

4.7uF

Cb

1uF

Rin1

Rin2

Rin3

Rin4

Cin2

4.7uF

Cin3

4.7uF

Cin4

4.7uF

RL

8Ohms

RL

8Ohms

Vcc

Vripple

1

2

4

3

14

12

11

9

10

BIAS

STBY

LEFT

RIGHT

LI N-

RIN-

LI N+

RIN+

Bypass

GND

GND

LOUT-

LOUT+

ROUT-

ROUT+

-

+

+

-

Vcc

TS4998

U1

TS4998 - QFN16

PSRR

20

Log

RMS

Output

()

RMS

Vripple

()

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

×

dB

()

=