Most industries, such as pharmaceutical, medical, biomedical, and industrial industries, all require precise temperature control in most of their processes. This is for three main reasons: 1) To properly manufacture or process the materials they are making, 2) Minimize the energy cost of their process and 3) Ensure safety and maximize the lifespan of their equipment. Renesas is providing a Winning Combination (See Figure 1 – US085 Block Diagram) reference design to give engineers a design that helps them achieve all those requirements in two basic ways. By minimizing the component count, it helps engineers reduce costs and enables a simpler board layout.
Let’s look at the heart of this design, the RX23E-A microcontroller (MCU). This MCU is equipped with an RXv2 32-bit core that excels in DSP/FPU operations, enabling high-accuracy measurement, digital filtering, control, and communication using a single chip. The main advantage of the RX23E-A MCU is that it is equipped with an analog front end that can measure temperature, pressure, flow, and weight with less than 0.1% precision without calibration, making it ideal for high-precision sensing. Another key feature is the dual 24-bit delta-sigma A/D converters with up to 23-bit effective resolution (without any external analog components). It also has a programmable data rate of 7.6sps to 15,625ksps, low RMS noise, low temperature drift, and integrated rail-to-rail PGAs. This makes the RX23E-A ideal for a temperature controller application.
Now let’s look at the power components of this Precision Industrial Temperature Control reference design. The ISL85415 is a 500mA synchronous buck regulator with an input range of 3V to 36V. The device provides a solution that is easy to use, has high efficiency, and a low BOM count for a variety of applications. It integrates both high-side and low-side MOSFETs and features a PFM mode for improved efficiency at light loads.
This feature can be disabled if forced PWM mode is desired. With a wide VIN range and reduced BOM count features, this part provides an easy design solution while giving superior performance. The other power component is the ISL9007, a high-performance LDO that delivers a continuous 400mA of load current. It has a low standby current and high PSRR and is stable with an output capacitance of 1µF to 10µF. It also has excellent load regulation with <0.1% voltage change across a full range of load current. These two products working together give engineers very stable and efficient power.
This reference design also provides analog components, such as the ISL3172E, a ±15kV ESD protected, RS-485/RS-422 transceiver with Tx/Rx. This high ESD protection makes it ideal for a robust industrial interface. The design also includes the ISL21090, an ultra-low noise, high DC accuracy precision voltage reference with a wide input voltage range. It is able to support a voltage accuracy of 0.02% (2.5V option).
With these product options, Renesas is showing engineers an option for a compact, low component count design for a high-precision temperature controller that is both robust and cost effective. It can also go into most industrial applications.
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