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REV. A

AD7866

–9–

Typical Performance Characteristics

FREQUENCY – kHz

–35

–115

0 500100

SNR – dB

200 300 400

–55

–75

–95

50 150 250 350 450

4098 POINT FFT

SAMPLE

= 1MSPS

= 300kHz

SNR = 70.31dB

THD = –85.47dB

SFDR = –86.64dB

–15

TPC 1. Dynamic Performance

INPUT FREQUENCY – Hz

–61

–75

10k 1M100k

SINAD – dB

–73

–63

–67

–69

–71

–65

= 25 C

= V

DRIVE

= 2.7V

= V

DRIVE

= 3.6V

= V

DRIVE

= 5.25V

= V

DRIVE

= 4.75V

TPC 2. SINAD vs. Input Frequency

RIPPLE FREQUENCY – Hz

–100

PSRR – dB

10k

–90

–80

–70

–60

–50

–40

–30

–20

–10

100k 1M

100mV p-p SINE WAVE ON AV

2.5V EXT REFERENCE ON V

REF

= 25

ⴗ

= 2.7V

= 5.25V

= 4.75V

= 3.6V

TPC 3a. PSRR vs. Supply Ripple Frequency,

without Supply Decoupling

RIPPLE FREQUENCY – Hz

–100

PSRR – dB

10k

–90

–80

–70

–60

–50

–40

–30

–20

–10

100k 1M

100mV p-p SINE WAVE ON AV

2.5V EXT REFERENCE ON D

CAP

A, D

CAP

= 25

ⴗ

= 2.7V

= 5.25V

= 4.75V

= 3.6V

TPC 3b. PSRR vs. Supply Ripple Frequency,

without Supply Decoupling

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.

TPCs 3a to 4b show the power supply rejection ratio versus

supply ripple frequency for the AD7866 under different

conditions. The power supply rejection ratio (PSRR) is defined

as the ratio of the power in the ADC output at full-scale fre-

quency f, to the power of a 100 mV sine wave applied to the

ADC AV

supply of frequency f

PSRR dB Pf Pf

()

10 log

Pf = power at frequency f in ADC output, and Pf

= power at

frequency f

coupled onto the ADC AV

supply. Here, a 100 mV

peak-to-peak sine wave is coupled onto the AV

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.

TPCs 5 and 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 the Analog

Input section.

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