Datasheet ATM90E26 (Microchip) - 14

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3.6 CALIBRATION
Calibration includes metering and measurement calibration. Metering Calibration The M90E26 design methodology guarantees the accuracy over the entire dynamic range, after metering calibration at one specific current, i.e. the basic current of Ib. The calibration procedure includes the following steps: 1. Calibrate gain at unity power factor; 2. Calibrate phase angle compensation at 0.5 inductive power factor. Generally, line current sampling is susceptible to the circuits around the sensor when shunt resistor is employed as the current sensor in L line. For example, the transformer in the energy meter’s power supply may conduct interference to the shunt resistor. Such interference will cause perceptible metering error, especially at low current conditions. The total inter- fere is at a statistically constant level. In this case, the M90E26 provides the power offset compensation feature to improve metering performance. L line and N line need to be calibrated sequentially. Reactive energy does not need to be calibrated after active energy cali- bration completed. Measurement Calibration Measurement calibration includes gain calibration for voltage rms and current rms. Considering the possible nonlinearity around zero caused by external components, the M90E26 also provides offset compensation for voltage rms, current rms, mean active power and mean reactive power. The M90E26 design methodology guarantees automatic calibration for frequency, phase angle and power factor measure- ment.
3.7 RESET
The M90E26 has an on-chip power supply monitor circuit with built-in hysteresis. The M90E26 only works within the volt- age range. The M90E26 has three means of reset: power-on reset, hardware reset and software reset. All registers resume to their default value after reset. Power-on Reset: Power-on reset is initiated during power-up. Refer to section 6.3. Hardware Reset: Hardware Reset is initiated when the reset pin is pulled low. The width of the reset signal should be over 200μs. Software Reset: Software Reset is initiated when ‘789AH’ is written to the software reset register (SoftReset, 00H). M90E26 [DATASHEET] 14 Atmel-46002B-SE-M90E26-Datasheet_110714 Document Outline Features Application Description Block Diagram 1 Pin Assignment 2 Pin Description 3 Functional Description 3.1 Dynamic Metering Range 3.2 Startup and No-Load Power 3.3 Energy Registers 3.4 N Line Metering and Anti-Tampering 3.4.1 Metering Mode and L/N Line Current Sampling Gain Configuration 3.4.2 Anti-Tampering Mode Threshold Compare Method Special Treatment at Low Power 3.5 Measurement and Zero-Crossing 3.5.1 Measurement 3.5.2 Zero-Crossing 3.6 Calibration 3.7 Reset 4 Interface 4.1 SPI Interface 4.1.1 Four-Wire Mode Read Sequence Write Sequence 4.1.2 Three-Wire Mode 4.1.3 Timeout and Protection 4.2 UART Interface 4.2.1 Byte Level Timing 4.2.2 Write Transaction 4.2.3 Read transaction 4.2.4 Checksum 4.3 WarnOut Pin for Fatal Error Warning 4.4 Low Cost Implementation in Isolation with MCU 5 Register 5.1 Register List 5.2 Status and Special Register SoftReset Software Reset SysStatus System Status FuncEn Function Enable SagTh Voltage Sag Threshold SmallPMod Small-Power Mode LastData Last Read/Write SPI/UART Value 5.3 Metering/ Measurement Calibration and Configuration 5.3.1 Metering Calibration and Configuration Register LSB RMS/Power 16-bit LSB CalStart Calibration Start Command PLconstH High Word of PL_Constant PLconstL Low Word of PL_Constant Lgain L Line Calibration Gain Lphi L Line Calibration Angle Ngain N Line Calibration Gain Nphi N Line Calibration Angle PStartTh Active Startup Power Threshold PNolTh Active No-Load Power Threshold QStartTh Reactive Startup Power Threshold QNolTh Reactive No-Load Power Threshold MMode Metering Mode Configuration CS1 Checksum 1 5.3.2 Measurement Calibration Register AdjStart Measurement Calibration Start Command Ugain Voltage rms Gain IgainL L Line Current rms Gain IgainN N Line Current rms Gain Uoffset Voltage Offset IoffsetL L Line Current Offset IoffsetN N Line Current Offset PoffsetL L Line Active Power Offset QoffsetL L Line Reactive Power Offset PoffsetN N Line Active Power Offset QoffsetN N Line Reactive Power Offset CS2 Checksum 2 5.4 Energy Register Theory of Energy Registers APenergy Forward Active Energy ANenergy Reverse Active Energy ATenergy Absolute Active Energy RPenergy Forward (Inductive) Reactive Energy RNenergy Reverse (Capacitive) Reactive Energy RTenergy Absolute Reactive Energy EnStatus Metering Status 5.5 Measurement Register Irms L Line Current rms Urms Voltage rms Pmean L Line Mean Active Power Qmean L Line Mean Reactive Power Freq Voltage Frequency PowerF L Line Power Factor Pangle Phase Angle between Voltage and L Line Current Smean L Line Mean Apparent Power Irms2 N Line Current rms Pmean2 N Line Mean Active Power Qmean2 N Line Mean Reactive Power PowerF2 N Line Power Factor Pangle2 Phase Angle between Voltage and N Line Current Smean2 N Line Mean Apparent Power 6 Electrical Specification 6.1 Electrical Specification 6.2 SPI Interface Timing 6.3 Power On Reset Timing 6.4 Zero-Crossing Timing 6.5 Voltage Sag Timing 6.6 Pulse Output 6.7 Absolute Maximum Rating Ordering Information Packaging Drawings Revision History