Datasheet AD7782 (Analog Devices) - 8

AD7782 Typical Performance Characteristics 9 3.0 8 2.5
ⴞ
2.56V RANGE 7 6 2.0 V
␮
– V 5 DD = 5V V 1.5 REF = 2.5V T 4 A = 25
ⴗ
C 3 RMS NOISE 1.0
ⴞ
160mV RANGE 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
The output rate of the AD7782 (fADC) equals:
Overview
f = 32 768 × 103 . / (69 × 8 × ) 3 The AD7782 incorporates an analog multiplexer with a Σ-∆ ADC ADC channel, on-chip programmable gain amplifier, and on-chip digital while the settling time equals: filtering intended for the measurement of wide dynamic range, low-frequency signals such as those in weigh-scale, strain-gage,  2  pressure transducer, or temperature measurement applications. t = 2 t SETTLE  f ADC ADC   = × This ADC input is buffered and can be programmed to have an input voltage range of ± 160 mV or ± 2.56 V. The input channels Normal-mode rejection is the major function of the digital filter on are configured as two fully differential inputs. Buffering the input the AD7782. Simultaneous 50 Hz and 60 Hz rejection of better channels means that the part can accommodate significant source than 60 dB is achieved as notches are placed at both 50 Hz and impedances on the analog inputs and that R, C filtering (for 60 Hz. Figure 4 shows the filter rejection. noise rejection or RFI reduction) can be placed on the analog inputs if required. The device requires an external reference of
0
+2.5 V nominal. Figure 3 shows the basic connections required to operate the part.
–20 –40 POWER SUPPLY 10
␮
F 0.1
␮
F dB – –60 TION A –80 –100 TTENU IN+ V A DD AD7782 –120 OUT+ OUT– AIN1(+) CS –140 AIN1(–) IN– DOUT/RDY
␮
CONTROLLER AIN2(+) –160 SCLK 0 10 20 30 40 50 60 70 80 90 100 AIN2(–) 10k
⍀
FREQUENCY – Hz XTAL1 REFIN(+) 32.768kHz OUTPUT DATA RATE = 19.8Hz CRYSTAL REFIN(–) INPUT BANDWIDTH = 4.74Hz XTAL2 6k
⍀
50Hz REJECTION = –66dB, 50Hz
ⴞ
1Hz REJECTION = –60dB GND 60Hz REJECTION = –117dB, 60Hz
ⴞ
1Hz REJECTION = –94dB
Figure 4. Filter Profile (Filter Notches at Figure 3. Basic Connection Diagram Both 50 Hz and 60 Hz) REV. A –7–