Getting Started with Anabit's RangeRite ADC
RangeRite ADC summary:
Anabit's RangeRite ADC family makes high-resolution dynamic measurements of both unipolar and bipolar signals simple and portable. The RangeRite ADC is available in four different resolution and sample rate versions:
- 16 bit resolution and 100 kSPS
- 16 bit resolution and 500 kSPS
- 18 bit resolution and 100 kSPS
- 18 bit resolution and 500 kSPS
Where the RangeRite gets its name is from its ability to change its input voltage range. The RangeRite has 4 different unipolar ranges (0 to 5.12V, 6.144V, 10.24V, 12.288V) and 5 bipolar ranges (+/- 2.56V, +/- 5.12V, +/- 6.144V, +/- 10.24V, +/- 12.288V). The RangeRite delivers these broad ranges in a small form factor from a single power input (6V to 18V). Best of all these ranges are controlled through its SPI interface and can be changed at any time between measurements.
Features and Technical Notes
RangeRite technical features:
- Includes an integrated ADC front end buffer amp and input termination of ≥ 1Mohm
- There is an onboard 4.096V precision voltage reference that can be accessed externally
- Noise filtering on the analog input before the buffer amp
- Integrated anti-aliasing filter with a cutoff frequency of 15 kHz, on both the 100 kSPS and 500 kSPS versions
Communicating and powering the RangeRite ADC:
- The RangeRite supports standard SPI communication with a max SPI clock rate of 66.67MHz. Uses SPI mode 0 with data read back MSB first.
- The RangeRite is powered off an input voltage between 6V and 18V, it consumes only 5mA of current so it is great for portable or remote applications.
- By default the digital circuits and logic run at 5V, but there is an optional digital power supply input on the RangeRite. Input an external digital supply between 1.8V and 5V to customize the voltage logic levels to match the microcontroller or microprocessor or using with the RangeRite.
- The RangeRite includes an on board LDO with a good PSRR specification as well as an LC filter on the analog supply to attenuate power noise so it does not add error to your precision analog measurement.
Protection and alarm features on the RangeRite ADC
- The ADC input features +/- 20V input overvoltage protection
- The design includes Zener diode over voltage protection on both the main power and digital power inputs
- It includes an alarm features that allows the user to program high and low thresholds for the ADC input. If the input goes beyond a set threshold the Alarm pin will go high
RangeRite Pin Description:
Below is a diagram of the RangeRite ADC's pins or connections. If you are facing the RangeRite's pin headers, the analog ADC input and voltage reference output pins are on the right. The input power, SPI communication, and hardware control pins are found on the left. The layout of the design was done to keep the noisy power and digital signals on one side of the design and the precision analog signals on other. The following is a description of the RangeRite pins:
- The VIN pin along with the GND pin is where to connect your 6V to 18V power source.
- The VDIG pin is optional and is meant for interfacing with a device like a microcontroller that does not use 5V logic. You can input a 1.8V to 5V power source along with a GND connection to power the digital circuits and set the logic level.
- The RST or reset pin (optional) will reset the ADC to its default power on state if it is pulled low. By default it is pulled high.
- The next four pins are used for SPI communication:
- SPI Clock (SCLK) pin is the input clock signal for the SPI communication.
- The Control In Peripheral Out (CIPO) pin is the communication line that fetches data from the ADC
- The Control Out Peripheral In (COPI) pin is the communication line that allows you to control settings on the ADC such as the input voltage range or alarm thresholds
- The Chip Select (CS) pin serves the traditional chip select role in standard SPI communication, but it is also used for controlling the start of a measurement.
- The ALM or Alarm pin (optional) is used to signal when there is an alarm condition. It is normally low and goes high when an alarm condition occurs.
- The RVS or Result Valid Signal pin (optional) is used to signal when an ADC conversion is complete and ready to read back via SPI. This pin is used in the below linked example code.
- The REF pin is where you can access the 4.096V precision voltage reference that is used by the ADC. Please note that this output voltage reference can only source about 100uA of current.
- The AIN is the input for the analog signal you are measuring
RangeRite ADC Example Arduino Code and Where to get Help:
The RangeRite example code was made to run in the Arduino programming environment and should work on any Arduino board that has hardware SPI capabilities. There are two different example code sketches available for the RangeRite ADC. The first just makes a single ADC measurement and prints it to the serial monitor. The second version takes a user defined amount of continuous measurements as fast as possible.
Links to the two versions of the RangeRite example code on github:
Have a question about the RangeRite ADC or run into any issues getting started with it? Please use the Anabit ADC Forum
RangeRite ADC Specifications:
- Firmware selectable input voltage ranges, note that ADC measurements are automatically scaled to the set voltage input range:
- Unipolar ranges: 0V to 5.12V, 6.144V, 10.24V, 12.288V
- Bipolar ranges: +/- 2.56V, +/- 5.12V, +/- 6.144V, +/- 10.24V, +/- 12.288V
- DC measurement accuracy specifications, giving in least significant bits (LSB) and % of reading:
- 18 bit versions: 3.10 LSB or 0.01 %
- 16 bit versions: 0.81 LSB or 0.01%
- Dynamic signal measurement accuracy giving in effective number of bits (ENOB):
- ENOB @ ~1 kHz for all versions: ~15 bits
- Includes built-in anti-aliasing low pass filter with cutoff frequency of ~15kHz. Filter cutoff frequency is the same for both maximum sample rate versions 100kSPS and 500kSPS
- Form factor: 51mm x 22mm with 2.54mm pin spacing. Mounting holes have a diameter of 3mm