AD7193 Analog Devices, AD7193 Datasheet - Page 54

• Manufacturer Part Number: AD7193
• Description: 4-Channel, 4.8 kHz, Ultralow Noise, 24-Bit Sigma-Delta ADC with PGA
• Manufacturer: Analog Devices

Specifications of AD7193

• Resolution (bits): 24bit
• # Chan: 4
• Sample Rate: n/a
• Interface: Ser,SPI
• Analog Input Type: Diff-Uni,SE-Uni,Usr-Defined Range/Offset
• Ain Range: ± (Vref/Gain)
• Adc Architecture: Sigma-Delta
• Pkg Type: SOP

AD7193
APPLICATIONS INFORMATION
The AD7193 provides a low cost, high resolution analog-to-digital
function. Because the analog-to-digital function is provided by a
Σ-∆ architecture, the part is more immune to noisy environments,
making it ideal for use in sensor measurement and industrial and
process control applications.
FLOWMETER
Figure 68 shows the AD7193 being used in a flowmeter application
that consists of two pressure transducers with the rate of flow
being equal to the pressure difference. The pressure transducers
are arranged in a bridge network and give a differential output
voltage between its OUT+ and OUT− terminals. With rated
full-scale pressure (in this case 300 mmHg) on the transducer,
the differential output voltage is 3 mV/V of the input voltage
(that is, the voltage between the IN+ and IN– terminals).
Assuming a 5 V excitation voltage, the full-scale output range
from the transducer is 15 mV. The excitation voltage for the
bridge can be used to directly provide the reference for the ADC,
because the reference input range includes the supply voltage.
A second advantage of using the AD7193 in transducer-based
applications is that the bridge power-down switch can be fully
utilized in low power applications. The bridge power-down switch
is connected in series with the cold side of the bridges. In normal
operation, the switch is closed and measurements are taken.
In applications where power is of concern, the AD7193 can be
placed in power-down mode, thus significantly reducing the
OUT–
IN–
IN+
OUT+
OUT–
IN–
IN+
5V
OUT+
Figure 68. Typical Application (Flowmeter)
REFIN1(+)
BPDSW
AIN1
AIN2
AIN3
AIN4
AIN5
AIN6
REFIN2(+)
REFIN2(–)
REFIN1(–)
AGND
MUX
AGND
Rev. C | Page 54 of 56
AGND
AV
AV
DD
DD
power consumed in the application. In addition, the bridge
power-down switch can be opened while the AD7193 is in power-
down mode, thus avoiding unnecessary power consumption
by the front-end transducers. When the parts are taken out of
power-down mode and the bridge power-down switch is closed,
the user should ensure that the front-end circuitry is fully settled
before attempting a read from the AD7193.
In Figure 68, temperature compensation is performed using
a thermistor. In addition, the reference voltage for the temperature
measurement is derived from a precision resistor in series with
the thermistor. This allows a ratiometric measurement so that
variation of the excitation voltage has no affect on the measurement
(it is the ratio of the precision reference resistance to the thermistor
resistance that is measured)
For simplicity, external filters are not shown in Figure 68; however,
an RC antialias filter must be included on each analog input.
This is required because the on-chip digital filter does not
provide any rejection around the modulator sampling frequency or
multiples of this frequency. Suitable values are a 100 Ω resistor
in series with each analog input, a 0.1 µF capacitor between the
analog input pins, and a 0.01 µF capacitor from each analog
input pin to AGND.
PGA
AD7193
DV
DD
Σ-Δ ADC
DGND
MCLK1 MCLK2
CIRCUITRY
CLOCK
INTERFACE
CONTROL
SERIAL
LOGIC
REFERENCE
AND
DETECT
DOUT/RDY
DIN
SCLK
CS
SYNC
Data Sheet