AD7843 Analog Devices, AD7843 Datasheet - Page 10

• Manufacturer Part Number: AD7843
• Description: Touch Screen Digitizer
• Manufacturer: Analog Devices

Specifications of AD7843

• Resolution (bits): 12bit
• # Chan: 4
• Sample Rate: 125kSPS
• Interface: Ser
• Analog Input Type: SE-Uni
• Ain Range: Uni (Vref)
• Adc Architecture: SAR
• Pkg Type: SOP

AD7843
–100
–120
–20
–40
–60
–80
0
0
V
100mV p-p SINEWAVE ON +V
f
SAMPLE
CC
10
Figure 16. AC PSRR vs. Supply Ripple Frequency
= 3V, V
= 125kHz,
20
REF
V
CC
30
= 2.5V
RIPPLE FREQUENCY (kHz)
f
IN
40
= 20kHz
50
CC
60
70
80
90
100
Rev. B | Page 10 of 20
Figure 16 shows the power supply rejection ratio versus V
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 f
applied to the ADC V
where:
Pf is the power at frequency f in ADC output.
Pfs is the power at frequency f
supply.
Here a 100 mV p-p sine wave is coupled onto the V
Decoupling capacitors of 10 µF and 0.1 µF were used on the
supply.
PSRR (dB) = 10 log (Pf/Pfs)
S
CC
to the power of a 100 mV sine wave
supply of frequency f
S
coupled onto the ADC V
S
:
CC
supply.
CC
CC