TSH344(2006) 查看數據表（PDF） - STMicroelectronics

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TSH344
(Rev.:2006)

340MHz Single-Supply Triple Video Buffer

STMicroelectronics 

TSH344

Power Supply Considerations and improvement of the PSRR

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

pin (pin 4) to improve high-frequency bypassing. A capacitor (CLF) greater than 100uF is

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

of 470nF (CHF) is added using the same implementation conditions to improve the PSRR in

the higher frequencies.

Figure 25. Circuit for power supply bypassing

+VCC

CLF

+

CHF

4

R

G

TSH344

B

5

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

0

Vcc=5V

-10 Load=150Ω

PSRR=20 log (∆VCC/∆Vout)

-20

-30

-40

-50

C =100uF

LF

C =470nF

HF

-60

without

capacitor

-70

-80

10k

100k

1M

10M

Frequency (Hz)

100M

Rev. 2

9/14

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