Smart Grid Solutions Guide - Maxim

Smart metersOverview• Field-upgradeable firmware toextend the useful life of themetering solution and allowpolicies to be dynamically adjustedto optimize energy usage• Polyphase monitoring and analysiscapabilities to help manage energyconsumption, enable load analysis,and optimize motor functions• LCD interface capable of supportingmultiple voltages and screenresolutions• Various levels of internal flashmemory sizes, along with externalmemory-management capabilitiesto support a wide portfolio of datastorage options• Several tamper-detection mechanismsto prevent energy theft;support for current transformers,Rogowski coils, and current shuntsalong with their combinationalcurrent-sensing mechanisms; opencurrent-sensor detection• Ability to work with single-wirepower measurement for specialtamper-detection conditionsfor single- and polyphase powermeasurements• Built-in real-time clock (RTC)functionalityReal-time clockMany metering AFEs integrate areasonably accurate RTC, which maydrift as much as 60 minutes/year. Thisinaccuracy should not be a problemif the meter is connected to a smartnetwork that periodically resynchronizesthe RTC. If the meter is notconnected to such a network, endcustomers will experience significantbilling discrepancies over time—unless, that is, a highly accurate RTCis used.Maxim has long offered the industry’smost accurate timekeeping solutionsfor metering applications. RTCssuch as the DS3231 monitor anonboard temperature sensor andadjust the load capacitance of anembedded crystal in order tocompensate for the natural temperaturevariation of the tuning forkcrystal. Because the crystal and dieare calibrated across the fulloperating temperature range asa unit, the resulting frequencyaccuracy is better than anycompeting technology. Theseproducts exceed the rigorousstandards for timekeeping accuracyin metering applications and arearmed with a multitude of advancedfeatures. Most importantly, theyeliminate the need for user calibration,providing a highly accuratesolution straight out of the box.Maxim’s new MEMS-based RTC,the DS3231M, extends the benefitsof the DS3231. The device’s allsiliconresonator enables thelow-frequency and low-currentcharacteristics of the crystalbasedDS3231 to be migrated to asmaller package. Additionally, theDS3231M offers extreme resilienceagainst high-temperature assemblyprocesses, can withstand shock andvibration in excess of 20Gs, andincludes offsets for aging.At the heart of the DS3231M is atemperature-compensated siliconoscillator. Based on measurementsfrom the DS3231M’s onboardtemperature sensor, a temperaturecompensationalgorithm automaticallyadjusts the resonantfrequency to account for temperatureeffects. This approach ensuresextremely tight accuracy overtemperature. Unlike crystal-basedproducts, the DS3231M exhibits lessthan ±0.5ppm of frequency shiftafter high-temperature reflows,and it maintains flat frequencystabilitycharacteristics (< ±5ppm)over the entire -40°C to +85°Ctemperature range.SummaryBy leveraging the flexible SoC featureset described above, manufacturerscan effectively address the range ofmetering options—from low-costfixed-function devices to premiumdevices that offer ample memory,reprogrammability, and highaccuracy. As the market for smartmeters continues to evolve, thisflexibility will enable meter manufacturersand utility companies to adaptto the needs of customers and thedictates of regulatory authorities, whilesimultaneously optimizing operationalefficiency and profitability.6 Maxim Smart Grid Solutions