Analog-to-digital converter, ADS805, the speed is not too fast, but in general it is enough, the overall comprehensive performance is still quite good.
It can be used in CCD imaging, digital baseband processing, copiers and test instruments.
characteristic:
1.20MHz, 12-bit, high dynamic range
2. High signal to noise ratio 68dB
3. Internal and external reference voltage
4. With input overshoot warning flag, this flag can be used in signal conditioning circuit for gain reduction adjustment
5. Digital error recognition technology guarantees good linearity
1 pin has a limit value indication function
15 pin is the output enable
18 pin selection for input range
19 pin is the reference voltage selection terminal
20, 22 pins are the bottom reference and top level reference respectively
23 pins are supplementary inputs
28 is the input output drive voltage
Figure 3 Timing diagram
As can be seen from the above timing diagram, one data conversion is completed in six time cycles.
This signal is an AC single-coupled cut-off form pointing to the ADS804, using a low distortion voltage feedback amplifier OPA642, and the top and bottom references (REFT, REFB) provide a +3V and +2V reference voltage, here two resistor pairs (2 x 2kΩ) It is a complementary input voltage used to create a common mode voltage of approximately +2.5V to the bias of the ADS805.
Such applications have requirements for the bandwidth of the signal, in which case the signal must be DC coupled to the A/D converter. To accomplish this, the interface circuit is used to provide a DC level change. The ADS805 typically operates at +2.5V common-mode voltage, which is determined by the two resistors R3 and R4, which are then input to the complementary input terminals R1, R2. Provide sufficient DC offset to attenuate the input noise signal.
Benchmark operating status:
The ADS805 is a bandgap reference circuit that includes logic to provide either a +1V or +2.5V reference output. Different reference voltages can be generated by two external resistor configurations. 
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