UAV flight control system can use ADC GX7689, compatible with AD7689

The UAV flight control system needs to accomplish complex control tasks, so the microprocessor should have rich and flexible interface resources, support floating-point arithmetic, and have programmable control capability to facilitate the completion of the current system design without expanding too many components externally. In addition, there is a need for high-precision A/D sampling circuit, signal conditioning circuits, a certain level conversion of the collected voltage signals and simple low-pass filtering process, and then output PWM control signals to control the servo to complete the control task.

A/D sampling is mainly used to realize the data acquisition function of the airspeed meter and altimeter, because the acquisition of analog information requires high sampling accuracy of the A/D chip, this paper recommends the use of external 16-bit sampling accuracy of the A/D converter chip GX7689 to complete the data acquisition function, and the use of SPI bus to realize the data communication between the off-chip A/D chip and the processor.

The GX7689 has all the components needed for a multi-channel, low-power data acquisition system, including: a lossless, true 16-bit SAR ADC; an 8-channel, low crosstalk multiplexer for configuring inputs as single-ended, differential, unipolar, or bipolar; an internal, low-temperature-drift, bandgap reference source (selectable from 2.5 V or 4.096 V) and buffer; temperature sensors; selectable unipolar filters; and an internal, low-temperature-drift bandgap reference source (selectable from 2.5 V or 4.096 V) and buffer when multiple channels are used in sequence. filter; and a sequencer useful when multiple channels are sampled sequentially.

GX7689 (AD7689 compatible) Features:

- Throughput speed: 250KSPS

- Integral nonlinearity: ±0.8LSB typical, ±1.6LSB worst case

- Dynamic range: 88dB

- Signal-to-noise distortion ratio: 87dB@2KHz

- Total harmonic distortion: -100dB@2KH

- Internal reference: 2.5V/4.096V selectable

- External retardation reference: up to 4.096V

- External reference: up to VDD

- Supports single analog power supply VDD