THD = 20 x log

+ . . . + A

A

f2

2

f10

2

Af1

2

ADC08B200

www.ti.com

SNAS388F – MARCH 2007 – REVISED APRIL 2013

zero scale (½ LSB below the first code transition) through positive full scale (½ LSB above the last code

transition). The deviation of any given code from this straight line is measured from the center of that code

value. The end point test method is used. Measured at 200 MSPS with a ramp input.

INTERMODULATION DISTORTION (IMD) is the creation of additional spectral components as a result of two

sinusoidal frequencies being applied to the ADC input at the same time. it is defined as the ratio of the

power in the second and third order intermodulation products to the power in one of the original

frequencies. IMD is usually expressed in dBFS.

MISSING CODES are those output codes that are skipped and will never appear at the ADC outputs. These

codes cannot be reached with any input value.

OFFSET ERROR is the error in the input voltage required to cause the first code transition. It is defined as the

difference between the voltage required to cause the first code transition and the ideal voltage (1/2 LSB)

to cause that transition.

where

•

(2)

OUTPUT DELAY is the time delay after the rising edge of the RCLK input before the data update is present at

the output pins.

OUTPUT HOLD TIME is the length of time that the output data is valid after the rise of CLK or RCLK output.

PIPELINE DELAY (LATENCY) is the number of clock cycles between initiation of conversion and when that

data is presented to the output driver stage. New data is available at every clock cycle, but the data lags

the conversion by the Pipeline Delay plus the Output Delay.

POWER SUPPLY REJECTION RATIO (PSRR) is a measure of how well the ADC rejects a change in the power

supply voltage. For the ADC08B200, PSRR1 is the ratio of the change in Full-Scale Error that results from

a change in the DC power supply voltage, expressed in dB. PSRR2 is a measure of how well an a.c.

signal riding upon the power supply is rejected at the output.

SIGNAL TO NOISE RATIO (SNR) is the ratio, expressed in dB, of the rms value of the input signal at the output

to the rms value of the sum of all other spectral components below one-half the sampling frequency, not

including harmonics or d.c.

SIGNAL TO NOISE PLUS DISTORTION (S/(N+D) or SINAD) is the ratio, expressed in dB, of the rms value of

the input signal at the output to the rms value of all of the other spectral components below half the clock

frequency, including harmonics but excluding d.c.

SPURIOUS FREE DYNAMIC RANGE (SFDR) is the difference, expressed in dB, between the rms values of the

input signal at the output and the peak spurious signal, where a spurious signal is any signal present in

the output spectrum that is not present at the input.

TOTAL HARMONIC DISTORTION (THD) is the ratio expressed in dB, of the rms total of the first nine harmonic

levels at the output to the level of the fundamental at the output. THD is calculated as

where

•

•

(3)

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