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FEATURES
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SA9604A THREE PHASE BIDIRECTIONAL POWER/ENERGY METERING IC WITH SERIAL SPI INTERFACE
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Performs bidirectional active and reactive power/energy measurement Voltage and frequency measurement Individual accessable phase information
Protected against ESD Uses current transformers for current sensing Excellent long term stability Operates over a wide temperature range Precision Voltage Reference on-chip
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SPI communication bus Meets the IEC 521/1036 Specification requirements for Class 1 AC Watt hour meters
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DESCRIPTION PIN CONNECTIONS The SAMES SA9604A Bidirectional Three Phase Power/Energy metering integrated circuit has a serial interface, ideal for use with a -Controller. The SA9604A performs 1 20 IVP2 IIP 2 the calculation for active and reactive power or energy, mains voltage sense and IIN2 2 19 IIN1 frequency. IVP3 3 18 IIP 1 The measurements performed and the IIP 3 4 17 IVP1 resultant register values are provided for individual phases. 5 16 G ND IIN3 The integrated values for active and reactive V DD 6 15 VREF energy, as well as the mains voltage sense and frequency information, are accessable F1 50 7 14 V SS through the SPI as 24 bit values. 8 13 CS SCK This innovative universal three phase power/ 9 12 DI D0 energy metering integrated circuit is ideally suited for energy calculations in applications O SC1 10 11 O SC2 such as primary industrial metering and factory energy metering and control. DR-01306 The SA9604A integrated circuit is available in both 20 pin dual-in-line plastic (DIP-20), Package: DIP-20 as well as 20 pin small outline (SOIC-20) SOIC-20 package types.
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SA9604A PDS039-SA9604A-001 REV. 5 29-05-00
SA9604A BLOCK DIAGRAM
V DD V SS
II P1 II N1 II P2 II N2 II P3 II N3
ACTIVE ENERGY
A N A LO G S IG N A L P ROCE S -
REACTIVE ENERGY VOLTAGE FREQUENCY SPI
DI DO SCK CS
I VP1 I VP2 I VP3 G ND
S IN G
F 150
VOLTAGE REF.
OS C
D R -01 3 0 7
VREF
O SC1 O SC2
ABSOLUTE MAXIMUM RATINGS* Parameter Symbol Supply Voltage VDD -VSS Current on any pin IPIN Storage Temperature TSTG Operating Temperature TO
Min -0.3 -150 -40 -40
Max 6.0 +150 +125 +85
Unit V mA C C
* Stresses above those listed under "Absolute Maximum Ratings" may cause permanent damage to the device. This is a stress rating only. Functional operation of the device at these or any other condition above those indicated in the operational sections of this specification, is not implied. Exposure to Absolute Maximum Ratings for extended periods may affect device reliability.
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SA9604A ELECTRICAL CHARACTERISTICS (VDD = 2.5V, VSS = -2.5V, over the temperature range -10C to +70C#, unless otherwise specified.) Parameter Symbol Operating temp. range TO Supply Voltage: Positive VDD Supply Voltage: Negative V SS Supply Current: Positive IDD Supply Current: Negative ISS Current Sensor Inputs (Differential) Input Current Range III Voltage Sensor Input (Asymetrical) Input Current Range IIV Pin DO Low Voltage V OL High Voltage VOH Pin DI High Voltage VIH Low Voltage VIL Pin SCK High Voltage Low Voltage VIH VIL fSCK tLO tHI Pin CS High Voltage Low Voltage Pin F150 Low Voltage High Voltage Oscillator Pin VREF Ref. Current Ref. Voltage
#
Min -25 2.25 -2.75
Typ
Max +85 2.75 -2.25 10 10 +25 +25 VSS+1
Unit C V V mA mA A A V V V V V V kHz s s V V V V
Condition
8 8 -25 -25
Peak value Peak value IOL = 5mA IOH = -2mA
VDD-1 VDD-1 VSS+1 VDD-1 VSS+1 800 0.6 0.6 VDD-1 VSS+1 VSS+1 VDD-1
VIN = VSS
VIN = VSS
VIH VIL V OL V OH
VIN = VSS IOL = 5mA IOH = -2mA
Recommended crystal: TV colour burst crystal f = 3.5795 MHz -I R VR 22.5 1.1 25 27.5 1.3 A V With R = 47k connected to VSS Reference to VSS
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Extended Operating Temperature Range available on request. sames
SA9604A PIN DESCRIPTION Pin 16 6 14 17 20 3 19 18 2 1 5 4 10 11 9 12 8 13 7 15 Designation GND VDD VSS IVP1 IVP2 IVP3 IIN1 IIP1 IIN2 IIP2 IIN3 IIP3 OSC1 OSC2 DO DI SCK CS FM150 VREF Connections for crystal or ceramic resonator (OSC1 = Input; OSC2 = Output) Serial Interface Out Serial Interface In Serial Clock In Chip Select (Active High) Voltage Sense Zero Crossover Connection for current setting resistor Input for Current sensor: Phase 3 Input for Current sensor: Phase 2 Description Ground Positive Supply Voltage Negative Supply Voltage Analog input for Voltage: Phase 1 Analog input for Voltage: Phase 2 Analog input for Voltage: Phase 3 Inputs for Current sensor:Phase 1
FUNCTIONAL DESCRIPTION The SA9604A is a CMOS mixed signal Analog/Digital Integrated Circuit, which performs the measurement of active power, reactive power, voltage and frequency. Internal offsets are eliminated through the use of cancellation procedures. The SA9604A integrates the measured active and reactive power consumption and the average mains voltage into 24 bit integrators, which are accessable via the SPI bus. The mains frequency information is also available as a 24 bit register value. The zero crossover of each voltage sense input is signalled on the FM150 (pin 7) output. This output of 150Hz will allow monitoring by a microcontroller to synchronise with internal timing for data aquisition. Refer to 5.5 for further information. The SA9604A has tristate output to allow connection of more than one metering device on a single SPI bus.
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SA9604A 1. Power calulation In the Application Circuit (Figure 1), the voltages from Line 1, Line 2 and Line 3, are converted to currents and applied to the voltage sense inputs IVN1, IVN2 and IVN3. The current levels on the voltage sense inputs are derived from the mains voltage (3 x 230 VAC ) being divided down through voltage dividers to 14VRMS. The resulting input currents into the A/D converters are 14ARMS through the resistors R15, R16 and R17. For the current sense inputs, the voltages across the current transformers terminating resistors are converted to currents of 16ARMS for rated conditions, by means of resistors R8, R9 (Phase 1); R10, R11 (Phase 2); and R 12, R13 (Phase 3). The signals providing the current information are applied to the current sensor inputs: IIN1; IIP1; IIN2; IIP2; IIN3; and IIP3. Analog Input Configuration The input circuitry of the current and voltage sensor inputs are illustrated below. These inputs are protected against electrostatic discharge through clamping diodes. The feedback loops from the outputs of the amplifiers AI and AV generate virtual shorts on the signal inputs. Exact copies of the input currents are generated for the following analog signal processing circuitry.
V DD
2.
II P
CURRENT SE NS OR INPUT S
V SS
A
V DD
I
II N
V SS VDD
IV P VOL T AGE SE NS OR INPUT
V SS
A
V
DR-0 1 3 0 8
GND
3.
Electrostatic Discharge (ESD), Protection The SA9604A Integrated Circuits inputs/outputs are protected against ESD. sames
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SA9604A 4. Power Consumption The power consumption rating of the SA9604A integrated circuit is less than 50mW. SPI - INTERFACE
5.
5.1 Description The serial peripheral interface (SPI) is a synchronous bus for data transfer and is used when interfacing the SA9604A with any micro-controller. Four pins are used for the SPI. The four pins are DO (Serial Data Out), DI (Serial Data In), CE (Chip Enable), and SCK (Serial Clock). The SA9604A is the slave device in an SPI application, with the micro-controller being the master. The DI and DO pins are the serial data input and output pins for the SA9604A, respectively. The CE input is used to initiate and terminate a data transfer. The SCK pin is used to synchronize data movement between the master (micro-controller) and the slave (SA9604A) devices. The serial clock (SCK), which is generated by the micro-controller, is active only during address and data transfer to any device on the SPI bus. 5.2 Register Access There are four registers for each phase which can be read: active, reactive, voltage and frequency. Any of these registers may be chosen as the initial register to read. If the SCK clock input continues after the first register has been read, the contents of subsequent registers will be output on the DO pin. Transfer will continue until CS is brough inactive. To enable registers for reading, the sequence 1 1 0 (6HEX) must precede the 6 bit address of the register being accessed. The various register addresses are shown in the table below:
ID 1 2 3 4 5 6 7 8 9 10 11 12
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REGISTER Active: Reactive: Voltage: Frequency: Active: Reactive: Voltage: Frequency: Active: Reactive: Voltage: Frequency: sames
Phase 1 Phase 1 Phase 1 Phase 1 Phase 2 Phase 2 Phase 2 Phase 2 Phase 3 Phase 3 Phase 3 Phase 3
A5 X X X X X X X X X X X X
A4 X X X X X X X X X X X X
A3 0 0 0 0 0 0 0 0 1 1 1 1
A2 0 0 0 0 1 1 1 1 0 0 0 0
A1 0 0 1 1 0 0 1 1 0 0 1 1
A0 0 1 0 1 0 1 0 1 0 1 0 1
SA9604A Address locations A4 and A5 have been included to ensure compatibility with future SAMES integrated circuit developments. When CS is high, data input on pin DI is clocked into the device on the rising edge of SCK. The data clocked into DI will comprise of 1 1 0 A5 A4 A3 A2 A1 A0, in this order. 5.3 Data Output After the least significant digit of the address has been entered on the rising edge of SCK, the output DO goes low with falling edge of SCK. Each subsequent falling edge transaction on the SCK pin will validate data of the register contents on pin DO. The contents of each register consists of 24 bits of data output on pin D0, starting with the most significant digit, D23. 5.4 Frequency Register For the frequency register only bits D15 ... D0 are used for calculations. The upper seven bits (D23 ... D17) must still be clocked out, as important frequency information can be derived from these data bits. Bit D17 changes with every rising edge of the mains voltage (25Hz square wave for 50Hz mains system). Bit D18 displays a frequency of D17/2 and D19 displays a frequency of D17/4. The phase error status may be ascertained from bits D20 and D21. The table below may be used for this purpose:
Frequency data Bits D21 D20 0 1 1 0 0 1
Description No phase error Phase sequence error (2 phase swapped) Missing phase
The phase error status is merged on all three frequency registers. Bits D16, D22 and D23 are not used.
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SA9604A 5.5 SPI Waveforms The read cycle waveforms are shown below:
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SA9604A SPI TIMING
Parameter Description t1 t2 t3 t4
Min Max Unit S S S S
SCK rising edge for data valid 1,160 Setup time for DI and CS before the rising edge 0,560 of SCK 0,625 SCK min high time SCK min low time 0,625
5.6 Synchronised Reading of Registers The SA9604A integrated circuit updates the registers on a continual basis. The SA9604A register content in latched onto the SPI interface as soon as a read command has been detected or the next register is addressed during continual access. The registers can be accessed at any time however for maximum stability the time between readings must be in multiples of 8 mains cycles. The internal offset cancellation procedure requires 8 mains cycles to complete. The registers are not reset after access, so in order to determine the correct register value the previous value read must be subtracted from the current reading. This methodology holds true for Active, Reactive and Voltage registers. The data read from the registers sames
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SA9604A represents the active power, reactive power and voltage integrated over time. The increase of decrease between readings is the energy consumption. The registers are not affected during access. No error is possible during read, because all control signals are generated on chip. The registers can be accessed in any sequence at any time without problems. The voltage sense zero crossing is a 1mS pulse available on FM150, (Pin 7). This information allows a supervisor (ie: microcontroller) to monitor when the next read operation should be performed. The FM150 output is only suitable if all phase voltages are connected. Should one or more phases fail the FM150 output becomes unstable. A better approach would be to monitor the upper bits of the frequency register (18, 19). A measurement cycle is completed when these bits change to the same state again (00..00 or 01..01 or 10..10 or 11..11).
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FM150 OUTPUT
Ph a se 1
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Ph a se 2 Ph a se 3 F 1mS +5 V
d r-0 1 4 6 4
An y se qu e nce o f 2 4 p ulse's is e q ua l to 1 m e asu re m en t cycle
SA9604A
0 V ( Vss)
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SA9604A 6. Register Values The 24 bit registers are up/down counters, which increment or decrement at a rate of 640k/s (640k*2/PI for reactive) at rated conditions. The energy register values will increment for positive energy flow and decrement for negative energy flow as can be seen in the following diagram:
register wrap around positive energy flow Register values 0 ............... H7FFFFF (8388607) H800000 ............... HFFFFFF (8388608) (16777215)
negative energy flow register wrap around
At power-up the register values are underfined and for this reason the msb of the delta value (delta value = present register value - previous register value) should be regarded as an indication of the measured energy direction. (0 = positive, 1 = negative). The delta value for the energy registers is between 0 and 8388607 for positive energy flow and between 0 and -8388607 for negative energy flow. For voltage the maximum usable delta value is 16777215 as voltage is in a positive direction only. When reading the registers care should be taken to check for a wrap around condition. As an example lets assume that with a constant load connected the delta value is 22260. Because of the constant load, the delta value should always be 22260 every time the register is read and the previous value subtracted (assuming the same time
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SA9604A period between reads). However this will not be true when a wrap around occurs as the following example will demonstrate: Previous register value = 16744955 Present register value = 16767215 Delta value = 16767215 - 16744955 = 22260 After the next read the values are as follows: Previous register value = 16767215 Present register value = 12260 Delta value = 12260 - 16767215 = -16754955 Computing this delta value will result in incorrect readings, in other words a wrap around has occurred. A typical function to check for wrap around condition would be as follows:
Function Check (delta_value); Begin Temp_delta_value = abs(delta_value); {get rid of the minus sign for example: abs(-151) = 151}
if Temp_delta_value)> 8388607 then begin if (delta_value)>0 then result : = (16777216-delta_value) *-1 else result : = (16777216+delta_value); end; end; {end function}
At rated conditions, the time for wrap around is as follows: 18.6 seconds for voltage 13 seconds for active and 21 seconds for reactive The active and reactive energy measured per count, may be calculated by applying the following formula: VI Watt seconds Energy per Count = K Where V I K = = = Rated Voltage Current (Imax) 640 000 for Active Energy 640 000 * 2 for Reactive Energy
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SA9604A Example: V = 230V I = 80A Active Power = 230V x 80A x (n/t)/640000
Reactive Power = 230V x 80A (n/t)/(640000 x 2)/Pi) n t = = Difference in register values between successive reads (delta value) Time difference between successive reads (in seconds) V *n 940 000 * t V= t= n= Rated Voltage Time difference between successive reads Difference in register values between successive reads
To calculate the measured voltage, the following formula is applied: V measured = Where
The Voltage calculated is the average voltage. The voltage measurement will give an accuracy of better than 1% for a voltage range of 50% to 115% of the rated mains voltage if the voltage is a pure sine wave. The mains frequency may be calculated as follows: Frequency = Crystal frequency Register Value * 2
7.
Calibration For accurate results we would recommend the following software calibration procedure: 7.1 Active energy Establish a calibration factor for active energy (Ka) at pf close to 1. Active Measured = Active_Register_Value x Ka
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SA9604A 7.2 Reactive Energy With a pf close to 0 establish the phase error: PhaseError = arctan (VARMeaured / ActiveMeasured) For each measurement calculate the following: VA = PHIcalibrated = PHICorrected = VARtrue = ActiveMeasured 2 + VARmeasured2 arctan (VARmeasured / ActiveMeasured) PHIcalibrated - PhaseError VA * sin(PHICorrected)
TYPICAL APPLICATION In the Application Circuit (Figure 1), the components required for a three phase energy metering application are shown. Terminated current sensors (current transformers) are connected to the current sensor inputs of the SA9604A through current setting resistors (R 8 ..R13). The resistor values for standard operation are selected for an input current of 16ARMS into the SA9604A, at the rated line current. The values of these resistors are calculated as follows: Phase 1: R8 = R9 = (I L1/16ARMS) * R18/2 Phase 2: R10 = R11 = (IL2/16A RMS) * R 19/2 Phase 3: R12 = R13 = (IL3/16A RMS) * R 20/2 Where ILX = Secondary CT current at rated conditions. R18, R19 and R20 = Current transformer termination resistors for the three phases. R1 + R1A, R4 and R15 set the current for the phase 1 voltage sense input. R2 + R2A, R5 + P 5 and R16 set the current for phase 2 and R 3 + R3A, R6 and R17 set the current for phase 3. The values should be selected so that the input currents into the voltage sense inputs (virtual ground) are set to 14ARMS for the rated line voltage condition. Capacitors C1, C2 and C3 are for decoupling and phase compensation. R14 defines all on-chip bias and reference currents. With R14 = 47k, optimum conditions are set. R14 may be varied by up to 10% for calibration purposes. Any changes to R14 will affect the output quadratically (i.e: R = +5%, P = +10%). XTAL is a colour burst TV crystal (f = 3.5795 MHz) for the oscillator. The oscillator frequency is divided down to 1.78975 MHz on-chip, to supply the digital circuitry and the A/D converters. sames
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SA9604A
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Figure 1: Application Circuit for Three Phase Power/Energy Measurement
M A IN S V O L T A G E S
R1 LINE 1 LINE 2 R2 R3 R2A R3A R1A
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LINE 3
R11 R19 VI2P VI2N GND R20 VI3P VI3N GND R6 VDD C3 R10 R17 R13 R12
1 2 3 4 5 6 7 8
20 19 18
R16 R8 R9 R15
C2 R18 VI1P C1 GND R4 R5 VDD VI1N
S A9604A IC -1
17 16 15 14 13 12 11
CS DI
R14
GND
F150 SCK D0 GND
9 10
D R -0 1 3 1 0
VSS R7 C13 C12
XTAL
GND
R21 C14
VSS
SA9604A Parts List for Application Circuit: Figure 1
Item 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 Symbol IC-1 XTAL R1 R1A R2 R2A R3 R3A R4 R5 R6 R7 R8 R9 R10 R11 R12 R13 R14 R15 R16 R17 R18 R19 R20 R21 C1 C2 C3 C12 C13 C14 Description Integrated circuit, SA9604A Crystal, 3.5795 MHz Resistor, 200k, 1%, 1/4W Resistor, 180k, 1%, 1/4W Resistor, 200k, 1%, 1/4W Resistor, 200k, 1%, 1/4W Resistor, 200k, 1% , 1/4W Resistor, 180k, 1%, 1/4W Resistor, 24k, 1%, 1/4W Resistor, 24k, 1%, 1/4W Resistor, 24k, 1%, 1/4W Resistor, 820, 1%, 1/4W Resistor Resistor Resistor Resistor Resistor Resistor Resistor, 47k, 1%, 1/4W Resistor, 1M, 1%, 1/4W Resistor, 1M, 1%, 1/4W Resistor, 1M, 1%, 1/4W Resistor Resistor Resistor Resistor, 820, 1%, 1/4W Capacitor, electrolytic, 1F, 6V Capacitor, electrolytic, 1F, 6V Capacitor, electrolytic, 1F, 6V Capacitor, 820nF Capacitor, 100nF Capacitor, 100nF Detail DIP-20, SOIC-20 Colour burst TV
Note 1 Note 1 Note 1 Note 1 Note 1 Note 1
Note 1 Note 1 Note 1 Note 2 Note 2 Note 2 Note 3
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SA9604A Resistor (R8, R9, R10, R11, R12 and R13) values are dependant upon the selected value of the current transformer termination resistors R18, R19 and R20. Note 2: Capacitor values may be selected to compensate for phase errors caused by the current transformers. Note 3: Capacitor (C12) to be positioned as close to Supply Pins (VDD & VSS) of IC-1, as possible ORDERING INFORMATION Part Number Package SA9604APA DIP-20 SA9604ASA SOIC-20 Note 1:
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SA9604A Notes:
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SA9604A
Disclaimer: The information contained in this document is confidential and proprietary to South African MicroElectronic Systems (Pty) Ltd ("SAMES") and may not be copied or disclosed to a third party, in whole or in part, without the express written consent of SAMES. The information contained herein is current as of the date of publication; however, delivery of this document shall not under any circumstances create any implication that the information contained herein is correct as of any time subsequent to such date. SAMES does not undertake to inform any recipient of this document of any changes in the information contained herein, and SAMES expressly reserves the right to make changes in such information, without notification,even if such changes would render information contained herein inaccurate or incomplete. SAMES makes no representation or warranty that any circuit designed by reference to the information contained herein, will function without errors and as intended by the designer.
Any sales or technical questions may be posted to our e-mail adress below: energy@sames.co.za For the latest updates on datasheets, please visit our web site: http://www.sames.co.za South African Micro-Electronic Systems (Pty) Ltd P O Box 15888, 33 Eland Street, Lynn East, Koedoespoort Industrial Area, 0039 Pretoria, Republic of South Africa, Republic of South Africa Tel: Fax: 012 333-6021 012 333-8071 Tel: Fax: Int +27 12 333-6021 Int +27 12 333-8071
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