The smart meter is an essential front-end component in all smart grid systems, allowing electricity consumption to be monitored in real-time. Two-way communication between the utility and the meter keeps accurate readings and saves customers from unnecessary charges on their electric bills. Unfortunately, implementing this type of system is impractical and expensive in certain countries from a “functionality-versus-cost” perspective. To fill this growing niche, Texas Instruments has compiled the Cost-optimized E-meter solution; a cost-effective smart-meter design that strikes a balance between communication options and advanced functionality with more memory (flash, RAM) to provide a value-line solution for mid-range smart utility metering.
Smart metering practicality
The benefits surrounding a smart meter equipped home are surmised by convenience and economy. Because smart meters provide up-to-date readings, monthly electric bills will reflect definite consumption instead of estimations. Simultaneously, the need to periodically send an agent to verify the meters is altogether abolished as data is automatically sent to the supplier.
With the proliferation of smart meters, customers will expect to access to same real-time data that their utility providers do, forcing providers to offer additional services that allow the interfacing between smart meters and smartphones, tablets, and computers. Having this detailed data pertaining to your energy habits allows a closer scrutiny of consumption patterns that in turn leads to power-saving strategies and a reduction in the overall monthly bill. Additionally, smart meters simplify the process of identifying any issues or faults pertaining to the power system to potentially reduce response time and make it easier for the utility company to fix the problem.
Transitioning to smart meters (utility challenges)
Shifting from traditional automatic meters to smart meters is the first step in embracing the smart grid. As such, energy companies must establish a solution that maintains the utmost possible data integrity because any mistake in reading is detrimental to company's reputation; this is especially important given the ease at which a customer can switch providers.
TI's Cost-optimized E-meter solution not only provides processing power and communication ports to implement all application and connectivity functions, but also benefits from an on-board analog-front-end (AFE) to measure power consumption and takes advantage of TI's other industry-leading innovations in metrology and wireless connectivity.
Solution features: MSP430F6736
Central to the solution is the MSP430F6736 smart meter, ultra-low-power, system-on-chip microcontroller. The device is part of the power 16-bit MSP430F6xxx family of products and supports robust single, dual, and three-phase metrology solutions.
MSP430F6736's CPU clocks in at 25 MHz, with up to 128 Kbytes of flash and 8 Kbytes of RAM. Its analog front end includes three optimized 24-bit analog-to-digital converters based on a second-order sigma-delta architecture that outputs a 24-bit result. The A/D converters can be stacked for simultaneous sampling of voltage and currents on the same trigger, allowing it to support single-phase with anti-tamper meter implementations.
The MCU also contains four enhanced universal serial communication interfaces (three eUSCI_A and one eUSCI_B), four 16-bit timers, hardware multiplier, DMA, real-time clock module with alarm capabilities, LCD driver with integrated contrast control, auxiliary supply system, and up to 72 I/O pins in 100-pin devices and 52 I/O pins in 80-pin devices.
CC2538
A second key component in the E-meter solution is the CC2538 RF system-on-chip. This component is both powerful and robust, combining a powerful ARM Cortex M3-based MCU system with up to 32 Kbytes of on-chip RAM and up to 512 Kbytes of on-chip flash to accommodate 2.4-GHz IEEE 802.15.4, 6LoWPAN and ZigBee applications. For this reason, CC2538 excels at handling complex network stacks with security, demanding applications, and over-the-air download.
The built-in security accelerators are powerful, accomplishing the authentication and encryption related tasks thus freeing up the CPU for other applications. Furthermore, transitioning from sleep to startup mode uses minimal energy on account of a low-power mode with retention.
TPS5432
Another highlight in the cost-optimized E-meter solution is the TPS5432 synchronous switching regular. TPS5432 supports smaller designs thanks to a current-mode control that reduces external component count, a 700-kHz switching frequency and integrated MOSFETs. The device is highly efficient, enabling 90% efficiency at light loads; TPS5432 provides accurate regulation for an assortment of loads across temperature.
ISO7131
ISO7131 is a low-power 2/1 triple-channel digital isolator with noise filter; it's designed to be integrated into a smart meter's common subsystems. The device has two forward and one reverse-direction channel and can supply galvanic isolation up to 2,500 VRMS for 1 minute per UL and 4242 VPK per VDE. ISO7131 provides a different speed depending on the power supply: 50 Mbits/s for 5-V supplies and 40 Mbits/s for 3.3- or 2.7-V supplies.
Additional components
The final components in the solution include the UCC28710 PWN controller, which provides isolate-output constant voltage (CV) and constant current (CC); the CC1200 fully integrated single-chip radio transceiver; the LM3671 DC/DC step-down converter; and the ISO3082 isolated 5-V full-duplex RS-485 transceiver.
Visit TI for closer examination of the Cost Optimized E-Meter solution
Orderable Part Numbers available at Mouser:
• MSP430F6736IPZ – Smart Meter SoC with on-board AFE
• TPS54327DRCT– Synchronous step down, high efficiency switching regulator
• ISO7131CCDBQ – Digital isolator with noise filter
• UCC28710D – Constant-voltage/current PWM controller
• CC1200RHBT – New! Low power, high performance RF transceiver
• LM3671MF-3.3/NOPB – Step-down DC-DC converter in versions with multiple outputs
• ISO3082DW – Isolated 5-V Full-Duplex RS-485 Transceiver
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