TSH343

Power Supply Considerations and improvement of the PSRR

Rev. 2

9/14

3

Power Supply Considerations and improvement of

the PSRR

Correct power supply bypassing is very important for optimizing performance in low and

high-frequency ranges. Bypass capacitors should be placed as close as possible to the IC

necessary to improve the PSRR in low frequencies. For better quality bypassing, a capacitor

the higher frequencies.

Figure 25. Circuit for power supply bypassing

The following graph in

Figure 26 shows the evolution of the PSRR against the frequency

when the power supply decoupling is achieved carefuly or not.

Figure 26. PSRR improvement

+

TSH343

Y

Pb

Pr

4

5

1k

10k

100k

1M

10M

100M

-80

-70

-60

-50

-40

-30

-20

-10

0

without C

LF

C

HF

=470nF

without C

LF

C

HF

=100nF

C

LF

=100uF

C

HF

=470nF

without

capacitor

Vcc=5V

Load=150

Ω

PSRR=20 log (

∆VCC/∆Vout)

Frequency (Hz)