Datasheet AD7676 (Analog Devices) - 8

AD7676 PIN CONFIGURATION NC NC NC NC NC IN+ NC NC NC IN– REFGND REF 48 47 46 45 44 43 42 41 40 39 38 37 AGND 1 36 AGND PIN 1 AVDD 2 IDENTIFIER 35 CNVST NC 3 34 PD BYTESWAP 4 33 RESET 5 OB/2C 32 CS NC 6 AD7676 31 RD TOP VIEW NC 7 30 (Not to Scale) DGND 8 SER/PAR 29 BUSY D0 9 28 D15 D1 10 27 D14 11 D2/DIVSCLK[0] 26 D13 D3/DIVSCLK[1] 12 25 D12 13 14 15 16 17 18 19 20 21 22 23 24 D D INT D D OR OGND OV DV DGND D9/SCLK D10/SYNC NC = NO CONNECT D4/EXT/ D8/SDOUT D5/INVSYNC D6/INVSCLK D7/RDC/SDIN D11/RDERR DEFINITION OF SPECIFICATIONS Effective Number of Bits (ENOB) Integral Nonlinearity Error (INL)
ENOB is a measurement of the resolution with a sine wave Integral nonlinearity is the maximum deviation of a straight line input. It is related to S/(N+D) by the following formula: drawn through the transfer function of the actual ADC. The deviation is measured from the middle of each code. ENOB = S / N ( [ + D] – .17 )6/ .602 dB
Differential Nonlinearity Error (DNL)
and is expressed in bits. In an ideal ADC, code transitions are 1 LSB apart. Differential
Total Harmonic Distortion (THD)
nonlinearity is the maximum deviation from this ideal value. It is THD is the ratio of the rms sum of the first five harmonic often specified in terms of resolution for which no missing codes components to the rms value of a full-scale input signal and is are guaranteed. expressed in decibels.
+Full-Scale Error Signal-to-Noise Ratio (SNR)
The last transition (from 011 . 10 to 011 . 11 in twos comple- SNR is the ratio of the rms value of the actual input signal to the ment coding) should occur for an analog voltage 1 1/2 LSB below rms sum of all other spectral components below the Nyquist the nominal +full scale (+2.499886 V for the ± 2.5 V range). The frequency, excluding harmonics and dc. The value for SNR is +full-scale error is the deviation of the actual level of the last expressed in decibels (dB). transition from the ideal level.
Signal-to-(Noise + Distortion) Ratio (S/[N+D]) –Full-Scale Error
S/(N+D) is the ratio of the rms value of the actual input signal The first transition (from 100 . 00 to 100 . 01 in twos comple- to the rms sum of all other spectral components below the ment coding) should occur for an analog voltage 1/2 LSB above Nyquist frequency, including harmonics but excluding dc. The the nominal –full scale (–2.499962 V for the ± 2.5 V range). The value for S/(N+D) is expressed in decibels (dB). –full-scale error is the deviation of the actual level of the last transition from the ideal level.
Aperture Delay
Aperture delay is a measure of the acquisition performance and
Bipolar Zero Error
is measured from the falling edge of the CNVST input to when The bipolar zero error is the difference between the ideal midscale the input signal is held for a conversion. input voltage (0 V) and the actual voltage producing the midscale output code.
Transient Response
The time required for the AD7676 to achieve its rated accuracy
Spurious-Free Dynamic Range (SFDR)
after a full-scale step function is applied to its input. The difference, in decibels (dB), between the rms amplitude of the input signal and the peak spurious signal. REV. B –7– Document Outline FEATURES APPLICATIONS GENERAL DESCRIPTION FUNCTIONAL BLOCK DIAGRAM PRODUCT HIGHLIGHTS SPECIFICATIONS RESOLUTION ANALOG INPUT THROUGHPUT SPEED DC ACCURACY AC ACCURACY SAMPLING DYNAMICS REFERENCE DIGITAL INPUTS DIGITAL OUTPUTS POWER SUPPLIES TEMPERATURE RANGE TIMING SPECIFICATIONS ABSOLUTE MAXIMUM RATINGS ORDERING GUIDE PIN FUNCTION DESCRIPTIONS PIN FUNCTION DESCRIPTIONS (continued) PIN CONFIGURATION DEFINITION OF SPECIFICATIONS Integral Nonlinearity Error (INL) Differential Nonlinearity Error (DNL) +Full-Scale Error –Full-Scale Error Bipolar Zero Error Spurious-Free Dynamic Range (SFDR) Effective Number of Bits (ENOB) Total Harmonic Distortion (THD) Signal-to-Noise Ratio (SNR) Signal-to-(Noise + Distortion) Ratio (S/[N+D]) Aperture Delay Transient Response Typical Performance Characteristics CIRCUIT INFORMATION CONVERTER OPERATION Transfer Functions TYPICAL CONNECTION DIAGRAM Analog Inputs Single-to-Differential Driver Driver Amplifier Choice Voltage Reference Input Power Supply POWER DISSIPATION CONVERSION CONTROL DIGITAL INTERFACE PARALLEL INTERFACE SERIAL INTERFACE MASTER SERIAL INTERFACE Internal Clock SLAVE SERIAL INTERFACE External Clock External Discontinuous Clock Data Read after Conversion External Clock Data Read During Conversion MICROPROCESSOR INTERFACING SPI Interface (MC68HC11) ADSP-21065L in Master Serial Interface APPLICATION HINTS Layout Evaluating the AD7676 Performance OUTLINE DIMENSIONS Revision History