MAXREFDES24#: 4 Chan. Signal Conditioner

The Alameda (MAXREFDES24#) subsystem reference design features four dense, highly accurate analog outputs in a compact, galvanically isolated form factor. Each channel provides current or voltage. This design uniquely fits in programmable logic controllers (PLC), distributed control systems (DCS), and other industrial applications. Hardware, firmware design files, and lab measurements are provided for rapid prototyping and development. The board is also available for purchase.

In PLC and DCS systems, analog output currents and voltages provide critical control and actuation functions. The Alameda (MAXREFDES24#) reference design shown in Figure 1 features four flexible and programmable analog outputs that meet industrial control requirements. The MAX5134 lies at the heart of the system. This four-channel, 16-bit, high-accuracy digital-to-analog converter (DAC) provides voltage outputs that drive the inputs of four MAX15500 signal conditioners. These signal conditioners produce user-programmable accurate current or voltage outputs. The MAX15500 also provides extensive error reporting. The MAX6126 produces an ultra-high-precision voltage reference for the DAC and the output conditioners. The MAX14850 galvanically isolates data communication from the field side and the system controller.

The Alameda also integrates an isolated, wide DC input range, flyback converter power supply. The peak current-mode flyback controller, MAX17498B, efficiently drives an isolated transformer and generates ±24V and +8V outputs. The MAX1659 low-dropout (LDO) linear regulator then regulates the +8V output to a +5V low-noise output. The entire system requires only a 24V input for power.

The subsystem features all typical bipolar current and voltage output ranges, and appropriate subsets, with less than ±0.1% typical total unadjusted error (TUE). The circuit also provides open-circuit detection, brownout detection, over-temperature protection, short-circuit and overcurrent protection, which are all critical for industrial applications. Flexible power-up options make Alameda an ideal choice for robust industrial control systems.