AD7843 查看數據表（PDF） - Analog Devices

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AD7843

Touch Screen Digitizer

Analog Devices 

AD7843

0

VCC = 3V, VREF = 2.5V

100mV p-p SINEWAVE ON +VCC

–20 fSAMPLE = 125kHz, fIN = 20kHz

–40

–60

–80

–100

–120

0

10 20 30 40 50 60 70 80 90 100

VCC RIPPLE FREQUENCY (kHz)

Figure 16. AC PSRR vs. Supply Ripple Frequency

Figure 16 shows the power supply rejection ratio versus VCC

supply frequency for the AD7843. The power supply rejection

ratio is defined as the ratio of the power in the ADC output at

full-scale frequency fS to the power of a 100 mV sine wave

applied to the ADC VCC supply of frequency fS:

PSRR (dB) = 10 log (Pf/Pfs)

where:

Pf is the power at frequency f in ADC output.

Pfs is the power at frequency fS coupled onto the ADC VCC

supply.

Here a 100 mV p-p sine wave is coupled onto the VCC supply.

Decoupling capacitors of 10 µF and 0.1 µF were used on the

supply.

Rev. B | Page 10 of 20

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