The design features a high-performance analogue front end and an embedded programmable gain amplifier, enhancing precision and cost-efficiency in energy measurement.
As global energy consumption rises, especially in the residential sector, utility providers need more precise and economical energy metering solutions. The Kinetis M series two-phase electricity meter reference design from NXP Semiconductors meets this demand by featuring a high-performance analogue front end paired with an embedded programmable gain amplifier. This combination enhances the accuracy of energy measurements, effectively addressing both precision and cost-efficiency needs.
The KM family comprises 32-bit microcontrollers utilizing 90nm Thin Film Storage (TFS) embedded flash technology, tailored primarily for the metering markets. These devices are designed for smart single-phase energy meters prevalent in India and China and two-phase meters used in the US, Japan, and Europe. The KM family adheres to metering standards such as EN 50470-1, EN 50470-3, IEC 62053-21, IEC 62053-22, and IEC 62053-23.
These microcontrollers feature a 32-bit ARM Cortex M0+ core, including an integrated Analog Front End (AFE). They offer CPU clock speeds of up to 50 MHz. Key components of the KM devices include a highly accurate Sigma Delta (SD) ADC, Programmable Gain Amplifier (PGA), precise internal voltage reference, flash memory, RAM, a phase compensation logic block, and additional peripherals. The KM family also supports tamper detection and includes an accurate real-time clock in all models, enhancing security and reliability in metering applications.
The design boasts a range of features for robust and precise energy measurement. It can handle currents up to 200 A and operates across a voltage range of 85 to 264 V at 50/60 Hz. Users have the flexibility of two installation options: Form 2S or Form 12S. The device adheres to the ANSI C12.20-2002 Class 0.2 accuracy class, ensuring reliable measurements. Additionally, it includes a line frequency measurement capability for precise zero-cross detection and implements a current transformer sensing circuit for each phase.
For energy conservation, the device features low-power modes that leverage a built-in RTC with Li-battery backup. It also includes an AMI expansion header that supports 2.4 GHz 802.15.4 or HAN/NAN communications via 6loWPAN IPv6 for Advanced Metering Infrastructure (AMI) and remote control functionalities. The design is EMC-proven according to ANSI C62.41 and IEC 61000-4-4, enhancing its resilience to electromagnetic interference.
On the peripherals front, the device is equipped with an 8 x 20 segment LCD with a charge pump and LED pulse outputs for measuring kWh and kVARh. Connectivity options include an isolated (4 kV) RS-232 port for monitoring, parameterization, and firmware upgrades and an optional infrared optical port compliant with ANSI C12.18-2006, broadening its utility and ease of integration into various systems.
NXP has tested this reference design. It comes with a bill of materials (BOM), schematics, assembly drawing, printed circuit board (PCB) layout, and more. The company’s website has additional data about the reference design. To read more about this reference design, click here.
