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licenses are implied. Maxim Integrated reserves the right to change the circuitry and specifications without notice at any time.
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Rev 4.0; 12/12 Maxim Integrated cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim Integrated product. No circuit patent licenses are implied. Maxim Integrated reserves the right to change the circuitry and specifications without notice at any time.
Updating the Demo Code (hex file) ......................... 19 1.9.4 Updating Calibration Data in Flash or EEPROM ..................... 20 1.9.5 Loading the Code for the 71M6541 into the Demo Board ................20 1.9.6 The Programming Interface of the 71M6541 ....................22 1.10 Demo Code ................................
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Placement of Sensors (IEC) ..........................55 2.6.4 Other Techniques for Avoiding Magnetic Crosstalk..................56 HARDWARE DESCRIPTION ..........................58 71M6541-DB Description: Jumpers, Switches and Test Points ............... 58 Board Hardware Specifications .......................... 62 APPENDIX ................................64 71M6541-DB Electrical Schematic ........................65 71M6541-DB Bill of Material ..........................
EEPROM, emulator port, and on-board power supply. A serial to USB converter allows communication to a PC through a USB port. The Demo Board allows the evaluation of the 71M6541 energy meter chip for measurement accuracy and overall system use.
Iso- Converter Figure 1-1: 71M6541-DB REV3.0 Demo Board with optional Debug Board: Basic Connections The Demo Board contains all circuits necessary for operation as a meter, including display, calibration LEDs, and internal power supply. Communication with a PC USB port is provided via connector CN1. The optional Debug Board uses a separate power supply, and is optically isolated from the Demo Board.
71M6541 Demo Board REV 3.0 User’s Manual 1.7.1 POWER SUPPLY SETUP There are several choices for the meter power supply: Internal (using the AC line voltage). The internal power supply is only suitable when the voltage ex- ceeds 100V RMS. To enable the internal supply, a jumper needs to be installed across JP6 on the top of the board.
The “HELLO” message should be followed by the display of accumulated energy: Wh SYS The “SYS” symbol will be blinking, indicating activity of the MPU inside the 71M6541. In general, the fields of the LCD are used as shown below:...
Before evaluating the 71M6541 on the Demo Board, users should get familiar with the commands and respons- es of the CLI. A complete description of the CLI is provided in section 1.8.1.
71M6541 Demo Board REV 3.0 User’s Manual 1.8.1 SERIAL COMMAND LANGUAGE The Demo Code residing in the flash memory of the 71M6541 provides a convenient way of examining and modifying key meter parameters via its command line interface (CLI). The tables in this chapter describe the commands in detail.
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71M6541 Demo Board REV 3.0 User’s Manual Commands for I/O RAM (Configuration RAM) and SFR Control: I/O RAM AND SFR CONTROL Comment Description: Allows the user to read from and write to DIO RAM and special function registers (SFRs). Usage: R [option] [register] …...
71M6541 Demo Board REV 3.0 User’s Manual Auxiliary Commands: Typing a comma (“,”) repeats the command issued from the previous command line. This is very helpful when examining the value at a certain address over time, such as the CE DRAM address for the temperature (0x40).
Read fuse 5 (TRIMBGA) Read fuse 6 (TRIMBGB). Example: Reads the TRIMM fuse. These commands are only accessible for the 71M6541H (0.1%) parts. When used on a 71M6541 (0.5%) part, the results will be displayed as zero. Rev 4.0...
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71M6541 Demo Board REV 3.0 User’s Manual Reset Commands: RESET Comment Description: Watchdog control Usage: Halts the Demo Code program, thus suppressing the trigger- ing of the hardware watchdog timer. This will cause a reset, if the watchdog timer is enabled.
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71M6541 Demo Board REV 3.0 User’s Manual Commands for Controlling the Metering Values Shown on the LCD Display: Text or Nu- Step merical Dis- Displayed Parameter(s) command play 10000 Meter ID 24.5 °C Temperature difference from calibration temperature. 59.9 Frequency at the VA_IN input [Hz] 3.27 Whr...
1.10.4. 1.8.5 USING THE PRE-AMPLIFIER In its default setting, the 71M6541 is applies a gain of 1 to the current input for phase A (IAP/IAN pins). This PRE_E gain is controlled with the bit in I/O RAM (refer to the IC data sheet).
71M6541 Demo Board REV 3.0 User’s Manual overvoltages. This choice need not be of concern, since the ADC in the 71M6541 has enough resolution, even when operating at 120Vrms or 240Vrms. If a different set of voltage-dividers or an external voltage transformer (potential transformer) is to be used, scaling techniques should be used.
71M6541 Demo Board REV 3.0 User’s Manual Table 1-4: CE RAM Locations for Calibration Constants CE Ad- Coefficient dress Description (hex) CAL_VA 0x11 Adjusts the gain of the voltage channels. +16384 is the typical value. The gain is directly proportional to the CAL parameter. Allowed range is 0 to 32767.
Writing 0xFF into the first few bytes of the EEPROM deactivates any calibration data previously stored to the EEPROM. 1.9.5 LOADING THE CODE FOR THE 71M6541 INTO THE DEMO BOARD Hardware Interface for Programming: The 71M6541F IC provides an interface for loading code into the inter- nal flash memory.
71M6541 Demo Board REV 3.0 User’s Manual Figure 1-5: Emulator Window Showing Reset and Erase Buttons (see Arrows) Figure 1-6: Emulator Window Showing Erased Flash Memory and File Load Menu Flash Programmer Module (TFP-2): The operational firmware of the TFP2 will have to be upgraded to revision 1.53.
71M6541 Demo Board REV 3.0 User’s Manual 1.9.6 THE PROGRAMMING INTERFACE OF THE 71M6541 Flash Downloader/ICE Interface Signals The signals listed in Table 1-5 are necessary for communication between the Flash Downloader or ICE and the 71M6541. Signal Direction Function...
71M6541 Demo Board REV 3.0 User’s Manual 1.10 DEMO CODE 1.10.1 DEMO CODE DESCRIPTION The Demo Board is shipped preloaded with Demo Code in the 71M6541F chip. The code revision can easily be verified by entering the command >i via the serial interface (see section 1.8.1). Check with your local Maxim In- tegrated representative or FAE for the latest revision.
71M6541 Demo Board REV 3.0 User’s Manual Table 1-6: MPU XRAM Locations Name Purpose Default Signed? Bits Metering element enters creep mode if current is below this value. If 0, creep logic is i_min Same units as CE’s i0sqsum. 0.08A signed disabled.
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71M6541 Demo Board REV 3.0 User’s Manual 407.3V = v_limit Error if exceeded.* Same units as CE’s v0sqsum. signed 240V*sqrt(2) *120% 3.2 Wh for 3- CE’s w0sum units per pulse, phase Convert from CE rounded up to next largest CE...
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71M6541 Demo Board REV 3.0 User’s Manual 0: Meter identification. (“#”) 1: Display variation from calibra- tion temperature, 0.1C 2: Display mains Hz, 0.1 Hz 3: mWh, total 4: mWh total exported. 5: mVARh, total. 6: mVARh, total exported. 7:mVAh, total 8: Operating hours.
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71M6541 Demo Board REV 3.0 User’s Manual Like i_max, except for the 2nd current sensor. Currents, Wh etc. i_max2 0.1 Amps 208 A (2080) signed using currents from the second sensor are rescaled into the same units as the first current sensor.
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71M6541 Demo Board REV 3.0 User’s Manual Bits: state_bit_ar Status of meter. 0 = no errors unsigned Nonvolatile. See table below. First 32-bit number is a count of pulses, =3.2 Wh in 3-phase me- Wh energy register. ters, or 1 in 1-phase. A fractional wh_im Nonvolatile.
High accuracy use of this feature may require a calibrated clock. IEC 62056 Manufacturers’ IDs are allocated by the FLAG Association Limited. Maxim Integrated does not own or profit from the FLAG association. Maxim Integrated’s default id may not conform, and is for demonstration purposes only.
71M6541 Demo Board REV 3.0 User’s Manual 1.10.3 LSB VALUES IN CE REGISTERS Table 1-8: CE Registers and Associated LSB Values Register Name LSB Value Comment The real energy for element 1 (IA, VA), measured in Wh per accumu- 1.55124*10...
= RMS voltage at the meter input corresponding to 176.8 mV RMS at the VA pin of the 71M6541. This value is determines by the divider ratio of the voltage-divider resistors. For the 71M6541 Demo Board, this value is 600.
After a brief delay, the Wh pulse LED (D5) will light up (SEGDIO0). The bootloader should send a ":" on the UART to the PC. If this occurs, the flash is erased, and the 71M6541-DB is ready to load code.
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71M6541 Demo Board REV 3.0 User’s Manual 6) Send the Intel hex file built for operation with the bootloader (e.g., 6541eq0_5p4g_07feb12.hex) using the ‘Send Text File’ command of HyperTerminal. 7) During the load procedure, the Wh LED will blink. Once the load process is completed it stops blinking. The Wh LED should remain on solidly at the completion of the load procedure, which indicates an error-free load.
71M6541 Demo Board REV 3.0 User’s Manual 2 APPLICATION INFORMATION 2.1 SENSOR CONNECTIONS AND EQUATIONS The 71M6541 Demo Board supports the following meter configurations and equations: • Single-phase two-wire (EQU 0) • Single-phase three-wire (EQU 1) Note: Support of EQU 2 requires the 71M6542 IC, which will be available on a separate Demo Board.
See the explanation below Table 1-8 for the calculation of A second current sensor can be connected to the IBP/IBP inputs of the 71M6541, for example to detect tamper- ing (see Figure 2-3). The second current sensor can be another shunt resistor that is isolated using the on- board 71M6X0X Remote Sensor Interface.
71M6541 Demo Board REV 3.0 User’s Manual in the primary channel, the CE code allows scaling between the two channels so that all energy calculations can IMAX be based on 2.1.3 SINGLE-PHASE THREE-WIRE (EQU 1) This meter configuration (see Figure 2-4) is used in North America (ANSI market) and parts of South America.
Note: In the formulae used in this section, the register /variable name is used. The CE code for the 71M6541 in reality uses a more advanced type of compensation that results in a delay adjust. The DLYADJ_A register name for this compensation factor is .
71M6541 Demo Board REV 3.0 User’s Manual 2.3 CALIBRATION PROCEDURES 2.3.1 CALIBRATION EQUIPMENT Calibration requires that a calibration system is used, i.e., equipment that applies accurate voltage, load current and load angle to the unit being calibrated, while measuring the response from the unit being calibrated in a re- peatable way.
PHADJ_n in the EEPROM or FLASH memory of the meter. If the calibration is performed on a Maxim Integrated Demo Board, the methods involving the command line interface, as shown in sections 1.9.3 and 1.9.4, can be used. Repeat the steps 1 through 7 for each phase.
Tip: Step 2 and the energy measurement at 0° of step 3 can be combined into one step. 2.3.6 CALIBRATION SPREADSHEETS Calibration spreadsheets are available from Maxim Integrated. Figure 2-7 shows the spreadsheet for three measurements. Figure 2-8 shows the spreadsheet for five measurements with three phases.
71M6541 Demo Board REV 3.0 User’s Manual 2.3.7 COMPENSATING FOR NON-LINEARITIES Nonlinearity is most noticeable at low currents, as shown in Figure 2-9, and can result from input noise and QUANT truncation. Nonlinearities can be eliminated using the variable. error...
71M6X0X Remote Sensor Interface IC. The reference voltage of the 71M6541 IC. At the temperature extremes, this voltage can deviate by a few mV from the room temperature voltage and can therefore contribute to some temperature-related error, both for the current measurement (pins IAP and IAN) of the secondary shunt sensor and for the voltage measurement (pin VA).
VA = voltage applied to the meter • IA = current applied to the shunt S1 that is connected to the IAP/IAN pins of the 71M6541 • IB = current applied to the shunt S2 that is connected via the Remote Interface IC •...
71M6541 Demo Board REV 3.0 User’s Manual 2.4.3 CALCULATING PARAMETERS FOR COMPENSATION 2.4.3.1 Shunt Resistors The TC of the shunt resistors can be characterized using a temperature chamber, a calibrated current, and a voltmeter with filtering capabilities. A few shunt resistors should be measured and their TC should be compared.
71M6541 Demo Board REV 3.0 User’s Manual GAIN_ADJ 16410 16400 GAIN_A… 16390 16380 16370 16360 16350 16340 16330 16320 16310 GAIN_ADJ Figure 2-10: over Temperature PPMC PPMC2 Some curve-fitting is required to find coefficients that will generate the desired behavior...
71M6541 Demo Board REV 3.0 User’s Manual 2.4.3.3 Reference Voltage of the 71M6541 At a later time, it will be shown how the compensation coefficients for the reference voltage of the 71M6541 can PPMC be derived. For the moment, let us assume that we know these coefficients, and that they are...
71M6541 Demo Board REV 3.0 User’s Manual For the control of GAIN_ADJB , we will need the following coefficients: : Since we assume that the shunt resistors are very similar with respect to their TC, we use the val- ue found for the shunt connected at phase B ( PPMC = -3331).
71M6541F tolerances was –3.41%, a range that can easily be compensated by calibration. Figure 2-14 shows a load-line obtained with a 71M6541 in differential mode. As can be seen, dynamic ranges of 2,000:1 for current can be achieved with good circuit design, layout, cabling, and, of course, good current sen- sors.
71M6541 Demo Board REV 3.0 User’s Manual The effect of shunt self-heating can be described by the following formulae. First, the relative output of a shunt resistor is: ΔV/V = ΔR/R ΔR is a function of the change in temperature, the temperature coefficient, the thermal resistance, and, of course, the applied power, which is proportional to the square of the current: ∆...
71M6541 Demo Board REV 3.0 User’s Manual 2.6.3 PLACEMENT OF SENSORS (IEC) The arrangement of the current terminals in a typical IEC meter enclosure predetermines the spacing of the shunts, and usually allows for only for 20 to 22 mm center-to-center spacing between the shunts. This means that the clearance between adjacent shunts is typically only 10 mm or less.
71M6541 Demo Board REV 3.0 User’s Manual 2.6.4 OTHER TECHNIQUES FOR AVOIDING MAGNETIC CROSSTALK With very high currents or close distances between shunt sensors, magnetic pickup or cross-talk will sometimes occur even if good placement practices are followed. One mechanism for cross-talk is shown in Figure 2-17, where the Manganin zone and the sensor wire act as a loop that will generate an output voltage similar to that generated by a Rogowski coil.
71M6541 Demo Board REV 3.0 User’s Manual 3 HARDWARE DESCRIPTION 3.1 71M6541-DB DESCRIPTION: JUMPERS, SWITCHES AND TEST POINTS The items described in the following tables refer to the flags in Figure 3-1. Reference Item # Name Designator GND test point.
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71M6541 Demo Board REV 3.0 User’s Manual Reference Item # Name Designator DEBUG Connector for Debug Board. 2x8 pin male header. Chip reset switch: When the switch is pressed, the RESET RESET pin of the IC is pulled high which resets the IC into a known state.
2-pin header connected to the VARh pulse LED 2-pin header for connection of the RX output of the isolated USB port to the RX pin of the 71M6541. When the Demo Board is communicating via the USB port, a jumper should UART_RX, ROUT be installed on JP5.
71M6541 Demo Board REV 3.0 User’s Manual 3.2 BOARD HARDWARE SPECIFICATIONS PCB Dimensions Width, length 134 mm x 131 mm (5.276” x 5.157”) Thickness 1.6mm (0.062”) Height w/ components 40 mm (1.57”) Environmental Operating Temperature -40°…+85°C Storage Temperature -40°C…+100°C Power Supply Using internal AC supply 100 V…240 V RMS...
71M6541 Demo Board REV 3.0 User’s Manual 4.2 71M6541-DB BILL OF MATERIAL Table 4-1: 71M6541-DB REV 3.0: Bill of Material Item Reference Part Footprint Digi-Key P/N Mouser P/N Manufacturer Manufacturer P/N Rating HDR DNP BAT 3 PIN BT1,BT2 BATTERY BARREL...
71M6541 Demo Board REV 3.0 User’s Manual 4.4 71M6541 PINOUT INFORMATION Power/Ground/NC Pins: Table 4-2: 71M6541 Pin Description Table 1/3 Name Type Description GNDA Analog ground: This pin should be connected directly to the ground plane. GNDD Digital ground: This pin should be connected directly to the ground plane.
71M6541 Demo Board REV 3.0 User’s Manual Digital Pins: Table 4-4: 71M6541 Pin Description Table 3/3 Name Type Description COM3,COM2, LCD Common Outputs: These 4 pins provide the select signals for the COM1,COM0 LCD display. Multi-use pins, configurable as either LCD segment driver or DIO. Al-...
Board’. Added USB Interface Module as part of Demo Kit Contents. Updated sample images of calibration spreadsheets and added text stating that spreadsheets are available on the Maxim Integrated web site. 12/12 Corrected part number for remote sensor IC (71M6601).
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