Datasheet AD7783 (Analog Devices) - 8

Typical Performance Characteristics–AD7783 9 3.0 8 2.5
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2.56V RANGE 7 6 2.0 V)
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VDD = 5V 5 V 1.5 REF = 2.5V TA = 25
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C 4 RMS NOISE (
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160mV RANGE 3 1.0 2 0.5 1 0 0 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 VREF (V) 8388039 8388382 8388449 8388499 8388547 8388579 8388615 8388657 8388687 8388721 8388754 8388779 8388805 8388841 8388874 8388906 8388941 8388985 8389033 8389110
TPC 1. Noise Distribution Histogram TPC 2. RMS Noise vs. Reference Input
ADC CIRCUIT INFORMATION Overview
The output rate of the AD7783 (fADC) equals The AD7783 incorporates a S-D ADC channel, on-chip pro- grammable gain amplifier, and on-chip digital filtering intended f = 32 768 ¥ 103 . / (69 ¥ 8 ¥ ) 3 ADC for the measurement of wide dynamic range, low frequency signals such as those in weigh-scale, strain gage, pressure trans- while the settling time equals ducer, or temperature measurement applications. = Ê 2 ˆ This ADC input is buffered and can be programmed to have an t 2 t SETTLE f ADC ËÁ ADC ¯˜ = ¥ input voltage range of ±160 mV or ±2.56 V. The input channel is configured as a fully differential input. Buffering the input Normal-mode rejection is the major function of the digital filter channel means that the part can accommodate significant source on the AD7783. Simultaneous 50 Hz and 60 Hz rejection of impedances on the analog input and that R, C filtering (for better than 60 dB is achieved as notches are placed at both 50 Hz noise rejection or RFI reduction) can be placed on the analog and 60 Hz. Figure 4 shows the filter rejection. input if required. The device requires an external reference of 2.5 V nominal. Figure 3 shows the basic connections required
0
to operate the part.
–20 POWER –40 SUPPLY 10
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F 0.1
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F –60 TION (dB) A –80 IN+ V –100 DD TTENU A AD7783 OUT+ OUT– AIN(+) –120 AIN(–) CS IN– –140 DOUT/RDY
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CONTROLLER IOUT1 SCLK 10k
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IOUT2 –160 0 10 20 30 40 50 60 70 80 90 100 XTAL1 FREQUENCY (Hz) REFIN(+) 32.768kHz CRYSTAL REFIN(–) OUTPUT DATA RATE = 19.8Hz XTAL2 6k
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INPUT BANDWIDTH = 4.74Hz GND 50Hz REJECTION = –66dB, 50Hz
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1Hz REJECTION = –60dB 60Hz REJECTION = –117dB, 60Hz
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1Hz REJECTION = –94dB
Figure 3. Basic Connection Diagram Figure 4. Filter Profile (Filter Notches at Both 50 Hz and 60 Hz) REV. C –7– Document Outline FEATURES INTERFACE POWER ON-CHIP FUNCTIONS APPLICATIONS FUNCTIONAL BLOCK DIAGRAM BASIC CONNECTION DIAGRAM GENERAL DESCRIPTION SPECIFICATIONS TIMING CHARACTERISTICS ABSOLUTE MAXIMUM RATINGS ORDERING GUIDE PIN CONFIGURATION PIN FUNCTION DESCRIPTIONS Typical Performance Characteristics ADC CIRCUIT INFORMATION Overview NOISE PERFORMANCE DIGITAL INTERFACE MASTER MODE (MODE = 0) SLAVE MODE (MODE = 1) CIRCUIT DESCRIPTION Analog Input Channel Programmable Gain Amplifier Bipolar Configuration/Output Coding Excitation Currents Crystal Oscillator Reference Input Grounding and Layout OUTLINE DIMENSIONS Revision History