Integration reduces total system chip count by 80 percent
Texas Instruments introduced the industry's first system-on-chip microcontroller unit (MCU) for electronic energy meters (e-meter). By combining an industry-standard ultra-low-power Flash MCU with an integrated high-performance analog front-end (AFE) on a single-chip, the mixed-signal integration of the new MSP430FE42x family of products reduces the total system chip count by eighty percent, improving performance and reliability, while reducing cost and time to market when compared to first generation electronic solutions.
With fully programmable communication capabilities, the MSP430FE42x family of application-specific MCUs is ideally suited for manufacturers developing electronic energy meters with sophisticated features such as automated meter reading (AMR), smart card prepayment and multiple rate billing
Systems using the MSP430FE42x family do not require multiple crystals, an EEPROM, LCD driver, external real time clock or expensive 5V power supplies. The reduced component count and the devices' inherent failsafe features increase overall reliability.
"Using the MSP430FE42x, designers can quickly develop hassle-free, high-performance energy meters", said Mark Buccini, MSP430 product line marketing manager for TI. "While performance is clearly increased, the automatic metrology function can cut critical time-to-market and cost in half."
In addition, this family of single-chip MCUs eliminates the need for expensive long-lead-time custom multi-chip AFEs. As a Flash memory MCU-based system, the same hardware can be used for many platforms with feature or country-specific changes made only in software. Because the Flash is in-system programmable, it is even possible to update a deployed meter to be updated remotely.
To provide the highest possible performance and simplify system design, the device integrates an embedded signal processor (ESP), ideal for single phase e-meters, plus the following key features to perform the energy metrology functions:
- Three independent 16-bit sigma-delta analog-to-digital converters operating at an over sampled rate of 1MHz;
- Three programmable gain amplifiers;
- A temperature sensor and a precision voltage reference.
The converted line voltage and current signals are digitally processed, providing:
- Energy and line period measurement;
- Negative power flow indication;
- Peak voltage and current;
- Phase and line-to-neutral current comparisons for tamper detection.
With precise phase matching between current and voltage channels, the ESP performs the necessary calculations to supply accurate active energy, apparent energy, RMS voltage, current and waveform samples. The ESP provides a 0.1percent accurate energy measurement over a dynamic current range of 1000 to 1, greatly surpassing the 1 percent accuracy common in typical mechanical meters. Having the ESP completely manage critical energy calculations enables the designer to utilize the freed-up central processor unit (CPU) functions for differentiated meter features such as display and AMR.
A flexible clock system with five low-power modes enables unmatched ultra-low-power performance and complete operation using only a single 32-kHz watch crystal. The low-frequency watch crystal, in combination with the integrated user-programmable, digitally-controlled oscillator, precisely meets system power and performance requirements. Supporting ultra-low power, the MSP430FE42x operates at 3V with the CPU and ESP active at only 2.5mA. In a power outage the device can operate in a standby mode with a typical current consumption of 1.1uA with a real-time-clock function active.
The family also includes standard MSP430 peripherals such as:
- an enhanced watchdog timer integrated LCD driver for up to 128 segments;
- brownout protection;
- supply voltage supervisor;
- three channel pulse width modulation timer;
- serial communication interface (Asynchronous UART or Synchronous SPI);
- serial onboard programming, which requires no external programming voltage.
The MSP430FE42x family is fully compatible with the existing $99 MSP-FET430P410 JTAG emulation toolkit. The tool supports real-time in-system application development, accessing the Flash device's embedded emulation capability. The tool comes complete with a JTAG interface, target board and a complete integrated development environment (IDE) including a debugger, assembler/linker and 4kB C-Compiler.
Texas Instruments Incorporated Semiconductor Group, SC-03139 Literature Response Center PO Box 954 Santa Clara, CA 91380 1-800-477-8924.