MAXQ314

19-5031; Rev 0; 11/09 TION KIT EVALUA BLE ILA AVA Single-Phase Power-Measurement IC with I2C Interface Features S High-Performance, Low-Power DSP Core S On-Chip Digital Temperature Sensor S Precision Internal Voltage Reference S Active Power (W), < ±0.5% Error S Reactive Power (VAR), < ±0.7% Error S Apparent Power (VA), < ±0.7% Error S Power Factor, < ±1% Error S Voltage RMS, < ±0.2% Error S Current RMS, < ±0.5% Error S I2C-Compatible Serial Interface S Continuous Output of IRMS in Serial or PWM General Description The MAXQ314 is a dedicated power-measurement IC that collects and calculates voltage, current, power, and power factor for a single-phase load. The results can be retrieved by an external master through the internal I2C bus. This bus is also used by the external master to configure the operation of the MAXQ314 and monitor the status of operations. The MAXQ314 performs voltage and current measurements using an integrated ADC that can measure voltage and current. Other values such as power are calculated from that data. The MAXQ314 also has an integrated temperature sensor that provides the die temperature on demand. The internal current amplifier produces up to 32x gain and the voltage amplifier gain is 1x. MAXQ314 Applications Single-Phase AC Power Monitoring Ordering Information PART MAXQ314+ OPERATING VOLTAGE (V) 3.0 to 3.6 TEMP RANGE -40NC to +85NC PIN-PACKAGE 20 TQFN-EP* +Denotes a lead(Pb)-free/RoHS-compliant package. *EP = Exposed pad. Block Diagram MAXQ314 MUX PGA ADC TEMP SENSOR VP VN IL INTERNAL REFERENCE WATCHDOG TIMER 16-BIT MAXQ20 RISC CPU SCL SDA A0 A1 A2 I2C INTERFACE BUS DSP SERIAL/PWM INTERNAL 8MHz CLOCK GENERATOR AUX AVDD AGND DVDD DGND POWER-ON RESET (AVDD, DVDD) RST MAXQ is a registered trademark of Maxim Integrated Products, Inc. Note: Some revisions of this device may incorporate deviations from published specifications known as errata. Multiple revisions of any device may be simultaneously available through various sales channels. For information about device errata, go to: www.maxim-ic.com/errata. _______________________________________________________________ Maxim Integrated Products 1 For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com. Single-Phase Power-Measurement IC with I2C Interface MAXQ314 TABLE OF CONTENTS Absolute Maximum Ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 Power-Monitoring Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 Electrical Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 I2C Electrical Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 I2C Bus Controller Timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 Pin Configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 Pin Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 Detailed Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 Clock Source . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 Reset Sources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 External Reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 Voltage Monitor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 I2C Slave Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 I2C Rate and Resets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 I2C Slave Address Generation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 I2C Protocol . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 Data and Control Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 Calibration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 Conversion to Physical Units . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 RMS Current Continuous Output (AUX Pin) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 Applications Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 Grounds and Bypassing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 Specific Design Considerations for MAXQ314-Based Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 Additional Documentation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 Development and Technical Support . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 Package Information. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 2 ______________________________________________________________________________________ Single-Phase Power-Measurement IC with I2C Interface MAXQ314 LIST OF FIGURES Figure 1. Series Resistors (RS) for Protecting Against High-Voltage Spikes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 Figure 2. I2C Bus Controller Timing Diagram. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 Figure 3. Calibration Circuit Example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 LIST OF TABLES Table 1. Slave Address Determination . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 Table 2. Register Set . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 Table 3. DSPCFG Register Detail. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 Table 4. Calibration Parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 _______________________________________________________________________________________ 3 Single-Phase Power-Measurement IC with I2C Interface MAXQ314 ABSOLUTE MAXIMUM RATINGS Voltage Range on DVDD with Respect to DGND ............................................. -0.3V Voltage Range on AVDD with Respect to AGND ............................................. -0.3V Voltage Range on AGND with Respect to DGND ............................................. -0.3V Voltage Range on AVDD with Respect to DVDD .............................................. -0.3V to +4.0V to +4.0V to +0.3V to +0.3V Voltage Range on Any Lead with Respect to (DGND = AGND) ............................... -0.3V to +4V Operating Temperature Range .......................... -40NC to +85NC Storage Temperature Range........................... -65NC to +150NC Continuous Power Dissipation (TA = +70NC) 20-Pin TQFN (derate 20.8mW/NC above +70NC) ....... 1667mW ESD Protection (Human Body Model) ...............................Q2kV Soldering Temperature ......................... Refer to the IPC/JEDEC J-STD-020 Specification. Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability. POWER-MONITORING SPECIFICATIONS (VAVDD = VDVDD = 3.0V to 3.6V, TA = +25NC.) (Note 1) PARAMETER Active-Power Error Reactive-Power Error Apparent-Power Error Power-Factor Error RMS Voltage Error RMS Current Error CONDITIONS Current input DR 500:1 Current input DR 500:1 Current input DR 500:1 Current input DR 500:1 Current input DR 30:1 Current input DR 500:1 MIN TYP 0.5 0.7 0.7 0.1 0.2 0.5 MAX UNITS % % % % % % ELECTRICAL CHARACTERISTICS (VAVDD = VDVDD = 3.0V to 3.6V, TA = +25NC, unless otherwise noted.) (Note 2) PARAMETER POWER SUPPLY Digital Supply Voltage Supply Current Analog Supply Voltage Supply Voltage Power-Fail Trip Point DIGITAL I/O Input High Voltage (RST) Input High Voltage (A0, A1, A2) Input Low Voltage (RST) Input Low Voltage (A0, A1, A2) VIH VIH2 VIL VIL2 2.1 VDVDD - 0.3 0.8 0.3 V V V V VDVDD IDVDD VAVDD UVLO Rising, VDVDD = VAVDD Hysteresis IDVDD + IAVDD, fCLK = 8MHz 3.0 2.75 2.8 100 3.0 6.5 3.6 15.0 3.6 2.95 V mA V V mV SYMBOL CONDITIONS MIN TYP MAX UNITS 4 ______________________________________________________________________________________ Single-Phase Power-Measurement IC with I2C Interface ELECTRICAL CHARACTERISTICS (continued) (VAVDD = VDVDD = 3.0V to 3.6V, TA = +25NC, unless otherwise noted.) (Note 2) PARAMETER Output Low Voltage (AUX) Input Leakage (A0, A1, A2) Input Capacitance (RST, A0, A1, A2) RST Pullup Resistance INTERNAL OSCILLATOR Oscillator Frequency Voltage Range (VP) Voltage Range (VN) Slow Current Channel (IL) Input Capacitance Single-Ended ADC Sampling Rate INTERNAL VOLTAGE REFERENCE Reference Accuracy TEMPERATURE SENSOR Temperature Accuracy TEP = -40NC to +85NC 3 NC TA = -40NC to +85NC 1.8 2.07 2.3 V Per channel SYMBOL VOL IL CIN RRST fSCLK 50 7.2 0 0 0 10 5 IOL = 6mA -12 10 150 8 200 8.8 1.5 1.5 1.5 CONDITIONS MIN TYP 0.4 +12 MAX UNITS V FA pF kI MHz V V V pF ksps MAXQ314 AFE AND ANALOG-TO-DIGITAL CONVERTER I2C ELECTRICAL CHARACTERISTICS (VAVDD = VDVDD = 3.0V to 3.6V, TA = -40NC to +85NC.) (Note 2) PARAMETER Input Low Voltage Input High Voltage Input Hysteresis (Schmitt) Output Logic-Low (Open Drain or Open Collector) Input Current on I/O I/O Capacitance SYMBOL VIL_I2C VIH_I2C VIHYS_I2C VOL_I2C IIN_I2C CIO_I2C VDVDD > 2V (Note 1) VDVDD > 2V, 6mA sink current Input voltage from 0.1 x VDVDD to 0.9 x VDVDD (Note 1) 0.7 x VDVDD 0.05 x VDVDD 0 -10 0.4 +10 10 CONDITIONS MIN MAX 0.3 x VDVDD UNITS V V V V FA pF _______________________________________________________________________________________ 5 Single-Phase Power-Measurement IC with I2C Interface MAXQ314 I2C BUS CONTROLLER TIMING (VDVDD = 3.0V to 3.6V, TA = +25NC, unless otherwise noted. Typical values are at VDVDD = 3.3V, TA = +25NC.) (Note 1, Figure 2) PARAMETER Serial Clock Frequency Bus Free Time Between a STOP and a START Condition Hold Time (Repeated) START Condition Repeated START Condition Setup Time STOP Condition Setup Time Data Hold Time Data Setup Time SCL Clock Low Period SCL Clock High Period Rise Time of Both SDA and SCL Signals Receiving Fall Time of Both SDA and SCL Signals Receiving Fall Time of SDA Transmitting Pulse Width of Spike Suppressed Capacitive Load for Each Bus Line SYMBOL fSCL tBUF tHD:STA tSU:STA tSU:STO tHD:DAT tSU:DAT tLOW tHIGH tR_I2C tF_I2C tF_TX tSP CB (Notes 4, 5) (Notes 4, 5) (Notes 4, 5) (Note 6) (Note 5) (Note 3) 120 1.3 0.6 20 + 0.1CB 20 + 0.1CB 20 + 0.1CB 300 300 250 50 400 1.3 0.6 0.6 0.6 0.9 CONDITIONS MIN TYP MAX 400 UNITS kHz Fs Fs Fs Fs Fs ns Fs Fs ns ns ns ns pF Note 1: Specifications guaranteed, but not production tested. Note 2: All parameters tested at TA = +25NC. Specifications over temperature are guaranteed by design. Note 3: A master device must provide a hold time of at least 300ns for the SDA signal (referred to VIL of the SCL signal) to bridge the undefined region of SCL’s falling edge. Note 4: ISINK P 6mA. tR_I2C and tF_I2C measured between 0.3 x VDVDD and 0.7 x VDVDD. Note 5: CB = Total capacitance of one bus line in pF. Note 6: Guaranteed by design. Input filters on the SDA and SCL pins suppress noise spikes less than 50ns. 6 ______________________________________________________________________________________ Single-Phase Power-Measurement IC with I2C Interface MAXQ314 VDVDD I2C DEVICE MAXQ314 RS SDA SCL RS I2C DEVICE RP RS RS RP Figure 1. Series Resistors (RS) for Protecting Against High-Voltage Spikes S SDA tF_I2C tLOW SCL tHD:STA tHIGH tR_I2C tSU:DAT SR P S tBUF tSU:STA tHD:DAT tSU:STO Figure 2. I2C Bus Controller Timing Diagram _______________________________________________________________________________________ 7 Single-Phase Power-Measurement IC with I2C Interface MAXQ314 Pin Configuration TOP VIEW RST REF VN A0 12 15 14 13 A1 11 VP 16 AVDD 17 AGND 18 IL 19 N.C. 20 10 9 A2 N.C. SDA SCL N.C. MAXQ314 8 7 + 1 AUX 2 N.C. 3 DGND 4 DVDD EP* 6 5 N.C. TQFN (5mm × 5mm) *EXPOSED PAD. Pin Description PIN 3 4 14 17 18 — NAME DGND DVDD REF AVDD AGND EP FUNCTION POWER PINS Digital Ground. AGND and DGND should be connected externally through a single point connection. Digital Supply Voltage. Connect AVDD to DVDD externally. Connect a 0.1FF capacitor to DGND. Buffered Reference Output. Connect this pin to AGND through a 1FF capacitor. No other signals should be connected to this pin. Analog Supply Voltage. Connect AVDD to DVDD externally. Connect a 0.1FF capacitor to AGND. Analog Ground. AGND and DGND should be connected externally through a single point connection. Exposed Pad. Connect to AGND. COMMUNICATION AND CONTROL PINS 1 7 8 10 11 12 13 AUX SCL SDA A2 A1 A0 RST Active-Low Reset Input. The CPU is held in reset when this pin is low. The pin includes pullup current source and should be driven by an open-drain external source capable of sinking in excess of 4mA. Device Selection Address Bits, Input. These bits select the slave address shown in Table 1. RMS Current Continuous Output. This open-drain pin continuously outputs the value of the most recent 16-bit RMS current measurement. If the SPCFG.PWMOUT bit is set, the value is instead output in PWM format. I2C Clock Line I/O I2C Data Line I/O 8 ______________________________________________________________________________________ Single-Phase Power-Measurement IC with I2C Interface Pin Description (continued) PIN 15 16 19 2, 5, 6, 9, 20 NAME VN VP IL Differential Voltage Negative Input Differential Voltage Positive Input Single-Ended Current Input, Low Frequency NO CONNECTION PINS N.C. No Connection. Do not connect any signal to this pin. FUNCTION VOLTAGE AND CURRENT MEASUREMENT PINS MAXQ314 Detailed Description The MAXQ314 is a dedicated analog front-end (AFE) that measures voltage, current, and temperature. The internal DSP then derives calculated values. It communicates with a master device using the I2C communication protocol, and continuously executes the following operations: • Scans AFE channels and collects raw voltage and current samples • Calculates power (real, reactive, apparent) • Responds to register write and read commands from the master It is the master device’s responsibility to ensure that all configuration registers have been set to their correct values in order to achieve the specified accuracy. An internal oscillator supplies a system clock of approximately 8MHz, varying slightly over temperature and voltage. No external components are needed. Voltage Monitor The device is held in reset any time the power supply AVDD drops below the supply voltage power-fail threshold. Once the power supply rises above the supply voltage power-fail level, the device exits reset, and all registers are reset to their defaults and execution resumes. I2C Slave Operation The MAXQ314 operates as an I2C slave peripheral and requires an external I2C master. All communications between the two are performed over a standard I2C bus, using commands to read and write values to internal registers. These registers contain: • Operating mode settings • Calibration parameters (supplied by the master) • Read-only registers containing power, current, and voltage data During operation, voltage and current measurements are taken, filtered, and the collected data is processed. The output results then can be read by the master from readonly registers in parallel with the ongoing measurement and processing operations. The device must be initialized by the master with configuration and calibration parameters following every power-up or reset cycle. Clock Source Reset Sources External Reset An external reset is generated by driving the RST pin low for at least 1Fs and remains as long as RST is held low. Once the external reset has been released, all registers are cleared to their default states, and the device resumes execution. _______________________________________________________________________________________ 9 Single-Phase Power-Measurement IC with I2C Interface MAXQ314 I2C Rate and Resets The I2C bus is dedicated to communications with the master device. The master device initiates all communications. During an I2C transfer, data is transmitted and received over the serial data line (SDA) with respect to a serial shift clock (SCL). I2C transfers always start with the most significant bit and end with the least significant bit. All I2C transfers are 8 bits in length, followed by an ACK/NACK bit. The clock rate used for the I2C interface is determined by the bus master, but can be at most 400kHz. The MAXQ314 can hold the SCL line low while processing commands to delay reception of further data. For frequencies at or below 100kHz, the delay can be transparent, but at 400kHz delays can be noticeable. A timeout provision resets the I2C controller if a low level is detected on the SCL pin for a period of 30ms. The I2C controller returns to its default state, and the SDA and SCL pins go their idle state. Table 1. Slave Address Determination A2 L L L L L L L L L Z Z Z Z Z Z Z Z Z H H H H H H H H H A1 L L L Z Z Z H H H L L L Z Z Z H H H L L L Z Z Z H H H A0 L Z H L Z H L Z H L Z H L Z H L Z H L Z H L Z H L Z H SLAVE ADDRESS :7 60h (1100 000b) 61h (1100 001b) 62h (1100 010b) 63h (1100 011b) 64h (1100 100b) 65h (1100 101b) 66h (1100 110b) 67h (1100 111b) 68h (1101 000b) 69h (1101 001b) 6Ah (1101 010b) 6Bh (1101 011b) 6Ch (1101 100b) 6Dh (1101 101b) 6Eh (1101 110b) 6Fh (1101 111b) 70h (1110 000b) 71h (1110 001b) 72h (1110 010b) 73h (1110 011b) 74h (1110 100b) 75h (1110 101b) 76h (1110 110b) 77h (1110 111b) 78h (1111 000b) 79h (1111 001b) 7Ah (1111 010b) I2C Slave Address Generation The A2, A1, and A0 pins are latched following every reset and used to construct the 7-bit slave address as shown in Table 1. The pin states are represented by L for logic 0, H for logic 1, and Z for high impedance. The I2C protocol supports bus timeout and optionally packet-error checking. When packet-error checking is enabled by setting the PECEN bit (DSPCFG.3) to 1, a packet-error code (PEC) byte is appended at the end of each transaction. The byte is calculated as CRC-8 checksum, calculated over the entire message including the address and read/write bit. The polynomial used is x8 + x2 + x + 1 (the CRC-8-ATM HEC algorithm, initialized to zero). Commands are read and write, the command code byte being an address of a register to read/write. Data length is 2 bytes for most registers, both read and write; 3 bytes for power (P, Q, S, PAVG), VRMS, and IRMS read commands. The MAXQ314 could be unable to report data like power, IRMS, VRMS, etc., immediately if the read command is received while the requested data is being calculated. In such a case, the clock line is held low until the calculation completes or a bus timeout occurs. The firmware does not support ARA address or address broadcast features. I2C Protocol 10 _____________________________________________________________________________________ Single-Phase Power-Measurement IC with I2C Interface Data and Control Registers All transactions consist of the master writing to or reading from data, configuration, or control registers. Each register has an 8-bit address. There are several categories of internal registers; read-only registers return measurement values taken by the device. All the read/write registers are calculation coefficients set by the master. The only exceptions are the DSPCFG register, which configures operating features of the device, and the ADC_AZ register, which resets the internal ADC when it is written to. MAXQ314 READ WORD S ADDR:7 W A CMD:8 A SR ADDR:7 R A D0:8 A D1:8 N P READ LONG S ADDR:7 W A CMD:8 A SR ADDR:7 R A D0:8 A D1:8 A D2:8 N P WRITE WORD S ADDR:7 W A CMD:8 A D0:8 A D1:8 A P READ WORD WITH PEC S ADDR:7 W A CMD:8 A SR ADDR:7 R A D0:8 A D1:8 A PEC:8 N P READ LONG WITH PEC S ADDR:7 W A CMD:8 A SR ADDR:7 R A D0:8 A D1:8 A D2:8 A PEC:8 N P WRITE WORD WITH PEC S ADDR:7 W A CMD:8 A D0:8 A D1:8 A PEC:8 A P A = ACKNOWLEDGE (ACK) BIT ADDR:7 = 7-BIT DEVICE ADDRESS; MUST MATCH THE ADDRESS SELECTED BY A[2:0] CMD:8 = REGISTER/COMMAND SELECTED IN TABLE 2 D0:8 = 8-BIT DATA; MULTIBYTE COMMANDS CAN REQUIRE D0, D1, D2, ETC. PEC:8 = 8-BIT PEC DATA N = NEGATIVE ACKNOWLEDGE (NACK) BIT P = STOP BIT S = START BIT SR = REPEATED START BIT W = WRITE BIT ______________________________________________________________________________________ 11 Single-Phase Power-Measurement IC with I2C Interface MAXQ314 Table 2. Register Set NAME P Q S PAVG VRMS IRMS PF RAWTEMP PA I_GAIN V_GAIN DSPCFG LPFC SUMCNT Active power Reactive power Apparent power Average power RMS-voltage RMS-current Power factor; LSB = 2-16 Temperature sample Phase-angle compensation coefficient Current gain coefficient Voltage gain coefficient DSP configuration Lowpass filter compensation Number of sampling frames per DSP cycle ADC autozero operation. The master issues this command only when it is initializing the MAXQ314. Any value written to this register initiates a reset of the ADC, which takes approximately 1.5ms to complete. Offset added to the P register Gain added to the P register Correction factor for IRMS calculation Voltage-dependent gain correction factor for IRMS calculation Offset for IRMS calculation Voltage-dependent offset for IRMS calculation DESCRIPTION ACCESS R R R R R R R R R/W R/W R/W R/W R/W R/W BITS 23:0 23:0 23:0 23:0 23:0 23:0 23:0 15:0 15:0 15:0 15:0 15:0 15:0 15:0 CMD CODE 0100 0010b (0x42) 0011 0010b (0x32) 0011 1010b (0x3A) 0101 1010b (0x5A) 0100 1010b (0x4A) 0101 0010b (0x52) 0011 1100b (0x3C) 0000 0111b (0x07) 0010 0100b (0x24) 0010 1011b (0x2B) 0010 1010b (0x2A) 0010 0010b (0x22) 0010 0011b (0x23) 0011 0100b (0x34) ADC_AZ W 7:0 0000 1111b (0x0F) P_OFFS P_GAIN IK IGV I_OFFS I_OV R/W R/W R/W R/W R/W R/W 15:0 15:0 15:0 15:0 15:0 15:0 84 8c B2 ba ac ac 12 _____________________________________________________________________________________ Single-Phase Power-Measurement IC with I2C Interface Table 3. DSPCFG Register Detail BIT 0 1 2 3 4 NAME DISIL RESERVED RESERVED PECEN AVGP 1 = disable IL measurements 0 = enable IL measurements (default) Must be set to 1 Must be set to 0 1 = PEC enabled for I2C transmission 0 = PEC disabled for I2C transmission (default) 1 = Begin accumulating PAVG 0 = Stop accumulating PAVG (default) 1 = PAVG calculation complete 0 = PAVG calculation in progress, following AVGP 1 R 0 (This bit is automatically cleared the next time the master sets AVGP to 1.) 1 = AUX pin outputs in PWM format 0 = AUX pin outputs in digital format (default) 1 = Disable gain switching 0 = Enable gain switching (recommended, default) 1 = PGA for IL = x4 (default) 0 = PGA for IL = x1 1 = AC mode 0 = DC mode (default) — Reset Status Indicator. These bits allow the master to determine if the MAXQ314 has performed a reset since the last time these bits were cleared. When these bits are 1111, the MAXQ314 has performed a reset. After the bits have been read, the master must write 0000 to these bits to clear the reset indicator. Writing to and reading from these bits does not affect processor operation or cause a reset; they are only status bits. DESCRIPTION MAXQ314 5 AVGRD 6 7 8 9 10:11 PWMOUT DISPGA ILPGA ACMODE RESERVED 12:15 RESET_STATUS ______________________________________________________________________________________ 13 Single-Phase Power-Measurement IC with I2C Interface MAXQ314 Calibration Four parameters can be calibrated to optimize system performance. The following equations convert “meter” units into physical units: Voltage (V) = VRMS x VTR x VREF/224 Current (A) = IRMS x ITR x VREF/224 Active Power (kW) = P x VTR x ITR x VREF x VREF/ (103 x 224) Reactive Power (kVAR) = Q x VTR x ITR x VREF x VREF/ (103 x 224) Apparent Power (kVA) = S x VTR x ITR x VREF x VREF/ (103 x 224) where VREF is the reference voltage on the REF pin in volts. The current RMS correction is: IRMS = I_OFFS + I_OV x VRMS + [(I_GAIN +IGV x VRMS)IMU + IK/IMU] where IMU is the current measured in meter units before correction. Voltage RMS correction is: VRMS = V_GAIN x VMU 749kΩ LOAD Conversion to Physical Units The output registers are in “meter” units, and need to be scaled with the input circuits to yield meaningful physical values. Two conversion coefficients are needed: the voltage transducer ratio (VTR) and the current transducer ratio (ITR), each specifying the ratio between the input and output of the corresponding transducer. The VTR represents the input voltage that would produce a 1V signal on the VP or VN pin. The ITR represents the input current that would produce a 1V signal on the IL pin. For example, if the voltage-sensing circuit consists of a 749kI and 1kI resistor-divider, then VTR = 750(V/V). If the current-sensing circuit is a 20mI shunt, then 50A current would produce 1V signal on the IL pin, so ITR = 50(A/V). LINE where VMU is the voltage measured in meter units before correction. VP Active power correction is: P = V_GAIN x I_GAIN x P_GAIN x (P_OFFS + PMU) MAXQ314 1kΩ where PMU is the active power measured in meter units before correction. Apparent power is computer from the corrected voltage and current: S = VRMS x IRMS Reactive power is computer from corrected S and P: Q = S2 − P2 IL 20mΩ NEUTRAL AGND Figure 3. Calibration Circuit Example Table 4. Calibration Parameters REGISTER V_GAIN I_GAIN PA DESCRIPTION Voltage Gain Factor. This factor affects the voltage RMS output and power output. The VRMS output is scaled by (1 + V_GAIN/216). V_GAIN is a signed integer and defaults to 0x0000h. Current Gain Factor. This factor affects the current RMS output and power output. The IRMS output is scaled by (1 + I_GAIN/216). I_GAIN is a signed integer and defaults to 0x0000h. Phase-Angle Compensation Lowpass Filter Coefficient. This factor affects the lowpass filtering. It can be left unchanged for typical configurations. It is defined as: LPFC ~ G x fC x tFR x 216, where fC is the corner frequency Default value ~ 3.14 x 1.82 (Hz) x 200 x E - 6 (s) x 216 = 75 = 0x004B LPFC 14 _____________________________________________________________________________________ Single-Phase Power-Measurement IC with I2C Interface MAXQ314 19 18 17 16 15 14 13 12 11 10 9 SYNC 1 1 0 0 8 7 6 5 4 3 2 1 0 FRAME GAP L L L L 1 19 18 17 16 15 14 13 12 11 10 9 SYNC 1 0 0 8 7 6 5 4 3 2 1 0 FRAME GAP L L L L SAMPLE DATA DDDDDDDDDDDDDDDD SAMPLE DATA DDDDDDDDDDDDDDDD RMS Current Continuous Output (AUX Pin) The AUX pin can be configured to output a 16-bit RMS current value. Bit time is 2000 system clocks, or a typical data rate of 4kbps. The bit format is pulse-width modulation, in which each bit cell is divided into four time slices. At the first time slice, the data line switches from a zero state to a one state. Then, if the bit to be transmitted is a zero, the data line switches back to zero after one time slice. If the bit to be transmitted is a one, the data line switches back to zero after three time slices. A data frame consists of one complete 20-bit sample word and a frame delimiter. The frame delimiter consists of the data line idling in a low state for nominally four bit times (tBIT). The receiver detects the first rising edge of the sync field and synchronizes on the 1100 pattern. The receiver should be synchronized by the time the first data bit is available. After 16 data bits, the data line becomes idle for four tBIT periods, after which the next synchronization bit begins. The AUX pin can output continuous PWM as well by setting the PWMOUT (DSPCFG.6) bit. The PWM output period is 65,535 system clocks, or 8.19ms. failure (damage to the silicon inside the device) or a soft failure (unintentional modification of memory contents). Voltage spikes above or below the device’s absolute maximum ratings can potentially cause a devastating IC latchup. Microcontrollers commonly experience negative voltage spikes through either their power pins or generalpurpose I/O pins. Negative voltage spikes on power pins are especially problematic as they directly couple to the internal power buses. Devices such as keypads can conduct electrostatic discharges directly into the microcontroller and seriously damage the device. System designers must protect components against these transients that can corrupt system memory. To reduce the possibility of coupling noise into the microcontroller, the systems that use an external crystal should be designed with a crystal in a metal case that is grounded to the digital plane. Doing so reduces the susceptibility of the design to fast transient noise. Specific Design Considerations for MAXQ314-Based Systems Applications Information Careful PCB layout significantly minimizes system-level digital noise that could interact with the microcontroller or peripheral components. The use of multilayer boards is essential to allow the use of dedicated power planes. The area under any digital components should be a continuous ground plane if possible. Keep any bypass capacitor leads short for best noise rejection and place the capacitors as close to the leads of the devices as possible. CMOS design guidelines for any semiconductor require that no pin be taken above supply voltage or below ground. Violation of this guideline can result in a hard Grounds and Bypassing Because the MAXQ314 is used in systems where high voltages are present, care must be taken to route all signal paths, both analog and digital, as far away as possible from the high-voltage components. It is possible to construct more elaborate metering designs using multiple MAXQ314 devices. This can be accomplished by using a single I2C bus, but with a different slave address for each device. Additional Documentation Designers must have the following documents to fully use all the features of this device. This data sheet contains pin descriptions, feature overviews, and electrical specifications. Errata sheets contain deviations from published specifications. • MAXQ314 data sheet, which contains electrical/timing specifications and pin descriptions • MAXQ314 revision-specific errata sheet (www.maxim-ic.com/errata) ______________________________________________________________________________________ 15 Single-Phase Power-Measurement IC with I2C Interface MAXQ314 Development and Technical Support Maxim offers the MAXQ314 evaluation kit (EV kit) as an aid in developing and prototyping applications based on the MAXQ314. The EV kit is a reference design from which a developer can begin designing their own system. The EV kit data sheet contains a schematic of the board that can be reviewed by engineers who want to perform a preliminary investigation of the device uses before purchasing the EV kit. Technical support is available at https://support.maximic.com/micro. Package Information For the latest package outline information and land patterns, go to www.maxim-ic.com/packages. Note that a “+”, “#”, or “-” in the package code indicates RoHS status only. Package drawings may show a different suffix character, but the drawing pertains to the package regardless of RoHS status. PACKAGE TYPE 20 TQFN-EP PACKAGE CODE T2055+4 DOCUMENT NO. 21-0140 Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are implied. Maxim reserves the right to change the circuitry and specifications without notice at any time. 16 © Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 2009 Maxim Integrated Products Maxim is a registered trademark of Maxim Integrated Products, Inc.