Control is though a four-wire digital interface to a host controller that clocks at up to 24MHz and is compatible with SPI, QSPI, Microwire and other protocols.
Each of the four channels on the other side of the chip can be software-configures as:
- Voltage input (0-10V, 200kΩ load option)
- Current input (external resistor)
- Voltage output (0-11V)
- Current output (0-25mA, HART compliant slew option)
- Digital input (de-bounce option, external switch sensing, for example)
- Resistance temperature sensor (RTD) measurement
Inputs are backed by a single 16-bit, Σ-∆ ADC shared between the four channels – with optional 50 Hz and 60 Hz rejection – and each channel gets its own inherently monotonic 13bit DAC. External reference voltages can be used instead of the internal reference.
As the chip, called AD74113R, is intended to be used in screw terminal modules, I-O lines are protected and tolerant to ±40 Vdc.
An on-chip charge-pump creates a negative rail so that outputs can extend all the way to 0V.
Voltage input mode can measure thermocouples by selecting the ±104.16mV input range via an internal register.
There is also an internal ±5°C accuracy temperature sensor.
An input edge counter is available in digital input mode.
To work, the IC needs three power rails: analogue (14 – 28.8V), internal digital (2.7 – 5.5V) and host interface (1.7 – 5.5V). The latter two can share a supply, and the host interface can be as low as 1.8V to allow SPI communications at 1.8V. Various internal LDOs are available to assist with power provisioning. The internally-generated negative rail is not available for external loads.
Operation is across -40°C to +105°C, and the package is a 64-lead LFCSP
A cheaper less capable version of the chip, without HART, is the AD74412R.
EV-AD74413RSDZ is an evaluation board for the AD74413R and can be controlled from a PC USB and Analog’s SDP-S system demonstration platform (SDP). A 14 to 28.8V supply is needed.
Product page links
AD74113R
AD74412R
EV-AD74413RSDZ