Datasheet AD7675 (Analog Devices) - 8

AD7675 PIN CONFIGURATION 48-Lead LQFP (ST-48) 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 AD7675 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 NC = NO CONNECT D D INT D D OR OGND OV DV DGND D9/SCLK D10/SYNC 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 nonlinearity is the maximum deviation from this ideal value. It
TOTAL HARMONIC DISTORTION (THD)
is often specified in terms of resolution for which no missing THD is the ratio of the rms sum of the first five harmonic codes are guaranteed. components to the rms value of a full-scale input signal and is expressed in decibels.
+FULL-SCALE ERROR
The last transition (from 011 . 10 to 011 . 11 in two’s
SIGNAL-TO-NOISE RATIO (SNR)
complement coding) should occur for an analog voltage 1 1/2 LSB SNR is the ratio of the rms value of the actual input signal to the below the nominal +full scale (+2.499886 V for the ±2.5 V range). rms sum of all other spectral components below the Nyquist The +full-scale error is the deviation of the actual level of the frequency, excluding harmonics and dc. The value for SNR is last transition from the ideal level. expressed in decibels.
–FULL-SCALE ERROR SIGNAL-TO-(NOISE + DISTORTION) RATIO (S/[N+D])
The first transition (from 100 . 00 to 100 . 01 in two’s S/(N+D) is the ratio of the rms value of the actual input signal complement coding) should occur for an analog voltage 1/2 LSB to the rms sum of all other spectral components below the above the nominal –full scale (–2.499962 V for the ±2.5 V range). Nyquist frequency, including harmonics but excluding dc. The The –full-scale error is the deviation of the actual level of the value for S/(N+D) is expressed in decibels. last transition from the ideal level.
APERTURE DELAY BIPOLAR ZERO ERROR
Aperture delay is a measure of the acquisition performance and The bipolar zero error is the difference between the ideal midscale is measured from the falling edge of the CNVST input to when input voltage (0 V) and the actual voltage producing the midscale the input signal is held for a conversion. output code.
TRANSIENT RESPONSE SPURIOUS FREE DYNAMIC RANGE (SFDR)
The time required for the AD7675 to achieve its rated accuracy The difference, in decibels (dB), between the rms amplitude of after a full-scale step function is applied to its input. the input signal and the peak spurious signal. REV. A –7– Document Outline FEATURES APPLICATIONS FUNCTIONAL BLOCK DIAGRAM PulSAR Selection GENERAL DESCRIPTION PRODUCT HIGHLIGHTS SPECIFICATIONS Table I. Serial Clock Timings in Master Read after Convert ABSOLUTE MAXIMUM RATINGS ORDERING GUIDE PIN FUNCTION DESCRIPTIONS 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 AD7675 Performance OUTLINE DIMENSIONS Revision History