AD7783 Analog Devices, AD7783 Datasheet - Page 7

• Manufacturer Part Number: AD7783
• Description: Single-Channel, Read-Only, Pin-Configured, 24-bit Sigma-Delta A/D Converter with Switchable Current Sources
• Manufacturer: Analog Devices

Specifications of AD7783

• Resolution (bits): 24bit
• # Chan: 1
• Sample Rate: n/a
• Interface: Ser,SPI
• Analog Input Type: Diff-Bip
• Ain Range: 0.32 V p-p,5.12 V p-p
• Adc Architecture: Sigma-Delta
• Pkg Type: SOP

REV. C
ADC CIRCUIT INFORMATION
Overview
The AD7783 incorporates a S-D ADC channel, on-chip pro-
grammable gain amplifier, and on-chip digital filtering intended
for the measurement of wide dynamic range, low frequency
signals such as those in weigh-scale, strain gage, pressure trans-
ducer, or temperature measurement applications.
This ADC input is buffered and can be programmed to have an
input voltage range of ± 160 mV or ± 2.56 V. The input channel
is configured as a fully differential input. Buffering the input
channel means that the part can accommodate significant source
impedances on the analog input and that R, C filtering (for
noise rejection or RFI reduction) can be placed on the analog
input if required. The device requires an external reference of
2.5 V nominal. Figure 3 shows the basic connections required
to operate the part.
OUT–
SUPPLY
POWER
IN+
IN–
9
8
7
6
5
4
3
2
1
0
Figure 3. Basic Connection Diagram
TPC 1. Noise Distribution Histogram
10 F
OUT+
10k
6k
0.1 F
AIN(+)
AIN(–)
IOUT1
IOUT2
REFIN(+)
REFIN(–)
AD7783
GND
V
DD
DOUT/RDY
XTAL1
XTAL2
SCLK
CS
32.768kHz
CRYSTAL
CONTROLLER
Typical Performance Characteristics–AD7783
–7–
The output rate of the AD7783 (f
while the settling time equals
Normal-mode rejection is the major function of the digital filter
on the AD7783. Simultaneous 50 Hz and 60 Hz rejection of
better than 60 dB is achieved as notches are placed at both 50 Hz
and 60 Hz. Figure 4 shows the filter rejection.
Figure 4. Filter Profile (Filter Notches at Both
50 Hz and 60 Hz)
–100
–120
–140
–160
–20
–40
–60
–80
1.5
1.0
3.0
2.5
2.0
0.5
0
0
1.0
0
OUTPUT DATA RATE = 19.8Hz
INPUT BANDWIDTH = 4.74Hz
50Hz REJECTION = –66dB, 50Hz
60Hz REJECTION = –117dB, 60Hz
TPC 2. RMS Noise vs. Reference Input
V
V
T
DD
REF
A
f
10
= 25 C
1.5
ADC
= 5V
= 2.5V
t
SETTLE
20
=
2.0
32 768 10
2.56V RANGE
30
.
=
2.5
Ê
Á
Ë
FREQUENCY (Hz)
40
f
¥
ADC
V
2
REF
3.0
50
ADC
ˆ
˜ = ¥
¯
3
(V)
/
1Hz REJECTION = –60dB
) equals
1Hz REJECTION = –94dB
60
2
(
69 8 3
3.5
160mV RANGE
t
¥ ¥
70
ADC
4.0
80
)
4.5
90
100
5.0