How Does The 4-20mA T 2 Click Board™ Work?
The 4-20mA T 2 Click Board™ is based on the DAC161S997, a low-power 16-bit ΣΔ digital-to-analog converter (DAC) from Texas Instruments, realized as a ΣΔ modulator. Next to ΣΔ DAC, the DAC161S997 also contains an internal ultra-low power voltage reference and an internal oscillator to reduce power and component count in compact loop-powered applications. This architecture, where DAC's output current represents a multiplied copy of the filtered modulator output, ensures an excellent linearity performance while minimizing the device's power consumption. In addition to an industry-standard 4-20 mA current loop over the LOOP terminal, the DAC161S997 also has the possibility of a simple Highway Addressable Remote Transducer (HART) modulator interfacing through an onboard HART TX terminal. It allows the injection of FSK-modulated digital data into the 4-20mA current loop.
The 4-20mA T 2 Click Board™ communicates with MCU using a 4-wire SPI serial interface with a maximum frequency of 10MHz, for data transfer and configuration of the DAC functions. The DAC161S997 supports both Mode 0 and Mode 3 of the SPI protocol. 4-20mA T 2 Click comes with an additional feature, as an interrupt, available on the ERR pin of the mikroBUS™ socket, the loop-error detection/reporting feature. By default, the DAC161S997 detects and reports several types of errors: loop error, SPI timeout error (channel error), frame error, and alarm current.
In the case of a fault condition or during the initial Power-Up sequence, the DAC161S997 will output current in either the upper or lower error current band. The band's choice is user-selectable via the appropriate position of an onboard jumper ERRL SEL, while the current error value is programmable through the SPI interface.
The 4-20mA T 2 Click Board™ can only operate with a 3.3V logic voltage level. The board must perform appropriate logic voltage level conversion before using MCUs with different logic levels. However, the Click board™ comes equipped with a library containing functions and an example code that can be used as a reference for further development.
SPECIFICATIONS
| Type | Current |
| Applications | It can be used for 2-wire 4-20mA current loop transmitters, industrial process control, low-power transmitters, and more |
| On-board modules | DAC161S997 - 16-bit DAC for 4-20mA loops from Texas Instruments |
| Key Features | High resolution, industry-standard current loop, SPI-programmable, low power consumption, Power-Up programmable output current, loop-error detection and reporting, HART modulator interfacing, and more |
| Interface | SPI |
| Compatibility | mikroBUS |
| Click board size | M (42.9 x 25.4 mm) |
| Input Voltage | 3.3V |
PINOUT DIAGRAM
This table shows how the pinout of the 4-20mA T 2 Click Board™ corresponds to the pinout on the mikroBUS™ socket (the latter shown in the two middle columns).
| Notes | Pin | Pin | Notes | ||||
|---|---|---|---|---|---|---|---|
| NC | 1 | AN | PWM | 16 | NC | ||
| NC | 2 | RST | INT | 15 | ERR | Loop-Error Interrupt | |
| SPI Chip Select | CS | 3 | CS | RX | 14 | NC | |
| SPI Clock | SCK | 4 | SCK | TX | 13 | NC | |
| SPI Data OUT | SDO | 5 | MISO | SCL | 12 | NC | |
| SPI Data IN | SDI | 6 | MOSI | SDA | 11 | NC | |
| Power Supply | 3.3V | 7 | 3.3V | 5V | 10 | NC | |
| Ground | GND | 8 | GND | GND | 9 | GND | Ground |
ONBOARD SETTINGS AND INDICATORS
| Label | Name | Default | Description |
|---|---|---|---|
| LD1 | PWR | - | Power LED Indicator |
| JP1 | ERRL SEL | Left | Power-Up Output Current Level Selection GND/VCC: Left position GND, Right position VCC |
4-20MA T 2 CLICK ELECTRICAL SPECIFICATIONS
| Description | Min | Typ | Max | Unit |
|---|---|---|---|---|
| Supply Voltage | - | 3.3 | - | V |
| Output Current | 4 | - | 20 | mA |