TI公司的智能水表和煤气表解决方案采用MSP430 16位超低功耗MCU MSP430x461x1, 2.4 GHz Zigbee 和802.15.4解决方案CC2510Fx/CC2511Fx,小于1GHz RF器件CC1110Fx/CC1111Fx, 850 – 950 MHz RF前端器件CC1190,以及RFID 预付费解决方案TRF7960/61和超低静态系统电源LM2840, LM2841或LM2842,马达驱动器与温度传感器TMP105等。本文介绍了智能水表和煤气表解决方案方框图和设计考虑以及主要器件的主要特性。

    图1.智能水表和煤气表解决方案方框图

    智能水表和煤气表设计考虑

    Gas and Water AMR （Automated Meter Reading） is an electronic metering （e-meter） technology that includes both the metrology and a one-way communication medium that collects and presents time synchronized interval meter data to utilities and provides usage profiles of customers" consumption over time. It combines high powered end points, network collectors, a data collection engine and fixed network technology to enable providers to know who is using how much gas and when.

    Gas and Water AMI （Advanced Metering Infrastructure）， sometimes referred to as smart metering, is a two way communications network that adds additional communication and control capability to AMR that can include valve control and customer access to consumption data.

    TI provides a broad portfolio of high-performance products that support many key features necessary for today"s AMR and AMI Smart Gas and Water Meters （from ultrasonic to mechanical）。

    TI智能水表和煤气表解决方案主要特性：

    1）Two-way Communication and Time Synchronized Measurement

    TI provides the Low Power RF portfolio （both sub-1 GHz and 2.4 GHz solutions） that interface with a TI MCU. This type of communication enables early leak detection in these meters as well as monitoring and customer awareness

    2）Logging and Billing

    With the implementation of flexible tariff rates it is critical to have a system where consumption information is logged. TI MCU solutions provide embedded flash technology to make this type of system a reality. In addition, TI provides solutions for anti-tamper and pre-payment RFID options for the ultimate in flexibility in today"s smart gas meters.

    3）Infrastructure life-time extension

    In order to optimize service frequency, battery life times in this type of application need to last 10-15 years. TI"s MSP430 Ultra Low Power MCU"s fit seamlessly into this thought process by combining high-performance with low power.

    4）Power

    As part of maximizing battery life, the correct selection of an ultra-low quiescent current power management device is a key to optimizing the low power of the MSP430. While running the MCU directly from the battery may work （within the specified MCU operating range） and seem to save the cost of power management components, the lack of voltage regulation means much higher MCU stand-by power consumption and lower battery life. This can lead to higher maintenance costs that will far offset any cost savings observed by eliminating the regulator. Regulating the MCU and peripheral communication ICs at the lowest possible voltage will optimize power savings and lengthen battery life.

    Depending on the type of battery used and the operating mode （full load） duty cycle of the meter, there are multiple choices in power management solutions. For simple, low duty cycle （long stand-by） applications, using batteries with a fairly flat discharge curve （such as primary cell Li-SOCl2） the use of ultra-low Iq LDOs can provide long battery life at very low cost. For higher operating duty cycle applications, the use of a low Iq DCDC regulator with power savings mode （for light loads） provides higher efficiency with a modest increase in cost.

    For applications using batteries with a linear discharge curve, such as multi-cell alkaline or NiXX, the use of a low-Iq buck/boost converter will maximize battery life by providing regulation down to discharge voltages as low as 1.8-volts. For use of single-cell or small coin cell batteries, where the battery voltage can be less than the regulated voltage, the use of low-Iq boost converters can provide regulation with input voltages as low as 0.7-volts.

    Although full operation of the MCU and peripheral communication ICs can be optimized at one voltage, in stand-by mode, these devices can operate at much lower voltages （simply maintaining RTC and memory）。 The use of DCDC converters and LDOs with dynamic voltage scaling （usually implemented with a V-Select logic pin） can further increase battery life.