AD7190
Data Sheet
Rev. C | Page 26 of 40
ADC CIRCUIT INFORMATION
MCLK1 MCLK2
P0/REFIN2(–) P1/REFIN2(+)
DVDD DGND
5V
AIN1
IN+
IN–
OUT–
OUT+
AIN2
AIN3
AIN4
AINCOM
REFIN1(–)
BPDSW
AGND
AD7190
REFIN1(+)
REFERENCE
DETECT
SERIAL
INTERFACE
AND
CONTROL
LOGIC
TEMP
SENSOR
CLOCK
CIRCUITRY
AVDD
AGND
DOUT/RDY
DIN
SCLK
CS
SYNC
P3
P2
AVDD
AGND
Σ-Δ
ADC
PGA
MUX
07640-
012
Figure 18. Basic Connection Diagram
OVERVIEW
The AD7190 is an ultralow noise ADC that incorporates a
∑- modulator, a buffer, PGA, and on-chip digital filtering
intended for the measurement of wide dynamic range signals
such as those in pressure transducers, weigh scales, and strain
gauge applications.
The part can be configured to have two differential inputs or four
pseudo differential inputs that can be buffered or unbuffered.
Figure 18 shows the basic connections required to operate the part.
FILTER, OUTPUT DATA RATE, SETTLING TIME
A ∑- ADC consists of a modulator followed by a digital filter.
The AD7190 has two filter options: a sinc3 filter and a sinc4
filter. The filter is selected using the SINC3 bit in the mode
register. When SINC3 is set to 0 (default value), the sinc4 filter is
selected. The sinc3 filter is selected when SINC3 is set to 1.
At low output data rates (<1 kHz), the noise-free resolution is
comparable for the two filter types. However, at the higher
output data rates, the sinc4 filter gives better noise free
resolution.
The sinc4 filter also leads to better 50 Hz and 60 Hz rejection.
While the notch positions are not affected by the order of the
filter, the higher order filter has wider notches, which leads to
better rejection in the band (±1 Hz) around the notches. It also
gives better stop-band attenuation. The benefit of the sinc3 filter
is its lower settling time for the same output data rate.
Chop Disabled
The output data rate (the rate at which conversions are available
on a single channel when the ADC is continuously converting)
is equal to
fADC = fCLK/(1024 × FS[9:0])
where:
fADC is the output data rate.
FS[9:0] is the decimal equivalent of Bit FS9 to Bit FS0 in the
mode register.
The output data rate can be programmed from 4.7 Hz to 4800 Hz;
that is, FS[9:0] can have a value from 1 to 1023.
The previous equation is valid for both the sinc3 and sinc4
filters. The settling time for the sinc4 filter is equal to
tSETTLE = 4/fADC
Whereas the settling time for the sinc3 filter is equal to
tSETTLE = 3/fADC
and sinc3 filters, respectively, for an output data rate of 50 Hz.
0
–10
–20
–30
–40
–50
–60
–70
–80
–90
–100
0
25
50
75
100
125
150
FILTE
R
GA
IN
(
dB
)
FREQUENCY (Hz)
07640-
013
Figure 19. Sinc4 Filter Response (50 Hz Output Data Rate)