AD7866 datasheet(8/20 Pages) AD

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REV. 0

AD7866

–8–

PERFORMANCE CURVES

TPC 1 shows a typical FFT plot for the AD7866 at 1 MHz sample

rate and 300 kHz input frequency. TPC 2 shows the signal-to-

(noise + distortion) ratio performance versus input frequency for

various supply voltages while sampling at 1 MSPS with an SCLK

of 20 MHz.

TPC 3a through TPC 4b show the power supply rejection ratio

versus AVDD supply ripple frequency for the AD7866 under differ-

ent conditions. The power supply rejection ratio is defined as the

ratio of the power in the ADC output at full-scale frequency f,

to the power of a 100 mV sine wave applied to the ADC AVDD

supply of frequency fS:

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

Typical Performance Characteristics

FREQUENCY – kHz

–35

–115

500

100

200

300

400

–55

–75

–95

150

250

350

450

4098 POINT FFT

SAMPLE = 1MSPS

fIN = 300kHz

SNR = 70.31dB

THD = –85.47dB

SFDR = –86.64dB

–15

TPC 1. Dynamic Performance

INPUT FREQUENCY – Hz

–61

–75

10k

1000k

100k

–73

–63

–67

–69

–71

–65

TA = 25 C

VDD = VDRIVE = 2.7V

VDD = VDRIVE = 3.6V

VDD = VDRIVE = 5.25V

VDD = VDRIVE = 4.75V

TPC 2. SINAD vs. Input Frequency

Pf = Power at frequency f in ADC output, PfS = power at fre-

quency fS coupled onto the ADC AVDD supply. Here a 100 mV

peak-to-peak sine wave is coupled onto the AVDD supply while

the digital supply is left unaltered. TPCs 3a and 3b show the

PSRR of the AD7866 when there is no decoupling on the supply,

while TPCs 4a and 4b show the PSRR with decoupling capacitors

of 10

µF and 0.1 µF on the supply.

TPC 5 and TPC 6 show typical DNL and INL plots for the AD7866.

TPC 7 shows a graph of the total harmonic distortion versus analog

input frequency for various source impedances.

TPC 8 shows a graph of total harmonic distortion versus analog

input frequency for various supply voltages. See Analog Input

section.

AVDD RIPPLE FREQUENCY – Hz

–100

10k

–90

–80

–70

–60

–50

–40

–30

–20

–10

100k

100mV p-p SINEWAVE ON AVDD

2.5V EXT REFERENCE ON VREF

TA = 25 C

VDD = 2.7V

VDD = 5.25V

VDD = 4.75V

VDD = 3.6V

TPC 3a. PSRR vs. Supply Ripple Frequency,

without Supply Decoupling

AVDD RIPPLE FREQUENCY – Hz

–100

10k

–90

–80

–70

–60

–50

–40

–30

–20

–10

100k

100mV p-p SINEWAVE ON AVDD

2.5V EXT REFERENCE ON DCAPA, DCAPB

TA = 25 C

VDD = 2.7V

VDD = 5.25V

VDD = 4.75V

VDD = 3.6V

TPC 3b. PSRR vs. Supply Ripple Frequency,

without Supply Decoupling

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