Datasheet

AD7747
Rev. 0 | Page 25 of 28
VOLTAGE INPUT
DIGITAL
FILTER
24-BIT Σ-Δ
MODULATOR
CLOCK
GENERATOR
ANALOG TO DIGITAL CONVERTER
(ADC)
05469-028
VOLTAGE
REFERENCE
DATA
VIN(–)
VIN(+)
REFIN(–)
REFIN(+)
R
REF
RTD
R
T
VDD
GND
Figure 38. Resistive Temperature Sensor Connected to the Voltage Input
The AD7747 Σ- core can work as a high resolution (up to
21 ENOB) classic ADC with a fully differential voltage input.
The ADC can be used either with the on-chip high precision,
low drift, 1.17 V voltage reference, or with an external reference
connected to the fully differential reference input pins.
The voltage and reference inputs are continuously sampled by
a Σ- modulator during the conversion. Therefore, the input
source impedance should be kept low. See the application
example in
Figure 38.
V
DD
MONITOR
Along with converting external voltages, the AD7747 Σ- ADC
can be used for monitoring the V
DD
voltage. The voltage from
the VDD pin is internally attenuated by 6.