Circuit function and advantage
The circuit shown in Figure 1 is a cost-effective, highly integrated 16-bit, 250 kSPS, 8-channel data acquisition system that digitally converts ±10 V industrial grade signals. The circuit also provides 2500 V rms isolation between the measurement circuit and the host controller, and the entire circuit is powered by an isolated PWM controlled 5 V single supply.
Figure 1. 16-bit, 250 KSPS, 8-channel data acquisition system (schematic diagram: all connections and decoupling are not shown) 
Circuit description
This circuit is used with the AD7689 16-bit, 8-channel, 250 kSPS PulSAR ADC and two low-cost precision quad op amps, the AD8608, to provide all signal conditioning and digitization in a data acquisition system. In addition, only the AD8605 op amp is required to buffer the reference voltage of the AD7689.
The AD8605 and AD8608 are low cost single and quad rail-to-rail input and output CMOS amplifiers, respectively. The AD8608 inverts, level shifts, and attenuates the ±10 V input signal to match the input range of the ADC. When using a +4.096 V reference and a +5 V single supply, the input range is 0 V to +4.096 V. .
The AD8605 acts as an external reference buffer to provide sufficient drive capability for level shifting. The AD8605 and AD8608 feature low offset voltage, low input voltage and current noise, and wide signal bandwidth, making them suitable for a wide range of applications. The low current and voltage noise of the AD8608 ensures that resistive noise is a major factor in high input impedance output noise. The input impedance (equal to R1) in this circuit is 50 kΩ.
16-Bit, 8-Channel, 250 kSPS PulSAR ADC The AD7689 contains all the components required for a multi-channel, low-power data acquisition system. It includes a 16-bit SAR ADC, an 8-channel low crosstalk multiplexer, a low drift reference and buffer, a temperature sensor, an optional single-pole filter, and a channel sequencer. The sequencer can be used to continuously scan channels without the need for a microcontroller or FPGA to control the channel switches. The AD7689 is available in a small 20-lead, 4 mm &TImes; 4 mm LFCSP package, resulting in minimal cost and printed circuit board (PCB) footprint. Operating temperature range is −40°C to +85°C. The 5 V power supply consumes 12.5 mW (typ) at 250 kSPS.
The ADuM3471 is a four-channel digital isolator with an integrated PWM controller and transformer driver to drive an isolated DC/DC converter. The ADuM3471 provides 5 V, 2 W isolated power to the circuit and isolates the digital signal from the SPI interface.
A transmitter sends both audio and video signals over the air waves. Transmitters usually transmit more than one signal (TV channel) at a time. A transmitter modulates both picture and sound into one signal and then send this transmission over a wide range to be received by a receiver (TV set).
It is an electronic device that radiates radio waves that carry a video signal representing moving images, along with a synchronized audio channel, which is received by television receivers ('televisions' or 'TVs') belonging to a public audience, which display the image on a screen.
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