Single Phase Power / Energy IC
with SPI Interface
sames
SA9903B
+ FEATURES
+ Bi-directional active
+
+
+
+
and reactive power/energy
measurement
RMS Voltage and frequency measurement
SPI communication bus
Meets the IEC 521/1036 Specification requirements for
Class 1 AC Watt hour meters
Meets the IEC 1268 Specification requirements for VAR
hour meters
Protected against ESD
Total power consumption rating below 25mW
Adaptable to different current sensor technologies
Operates over a wide temperature range
Precision voltage reference on-chip
+
+
+
+
+
DESCRIPTION
The SAMES SA9903B is a single phase bi-directional
energy/power metering integrated circuit that performs
measurement of active and reactive power, mains voltage and
mains frequency.
This innovative universal single phase power/energy metering
integrated circuit is ideally suited for energy calculations in
applications such as electricity dispensing systems (ED's),
residential municipal metering and factory energy metering
and control.
The SA9903B is pin compatible to the SA9603B. New features
include, RMS mains voltage and accurate reactive power
measurements.
TheSA9903B integrated circuit is available in both 20 pin dualin-line plastic (DIP-20), as well as 20 pin small outline (SOIC20) package types.
Measured values for active and reactive energy, the mains
voltage and frequency are accessible through a SPI bus from
24 bit registers.
TEST
VDD
VSS
ACTIVE
IIP
CURRENT
ADC
IIN
DI
DO
REACTIVE
SPI
RMS
VOLTAGE
IVP
SCK
CS
VOLTAGE
ADC
MAINS.
FREQ.
FMO
VOLTAGE
REF.
GND
OSC
Dr-01583
VREF
OSC1
OSC2
Figure 1: Block diagram
SPEC-0051 (REV. 2)
1/12
26-02-01
sames
SA9903B
ELECTRICAL CHARACTERISTICS
(VDD = 2.5V, VSS = -2.5V, over the temperature range -10°C to +70°C#, unless otherwise specified.)
Symbol
Min
Operating temp. Range
TO
Supply Voltage: Positive
Typ
Max
Unit
-25
+85
°C
VDD
2.25
2.75
V
Supply Voltage: Negative
VSS
-2.75
-2.25
V
Supply Current: Positive
IDD
3.56
5.1
mA
Supply Current: Negative
ISS
3.56
5.1
mA
Parameter
Condition
Current Sensor Inputs (Differential)
Input Current Range
III
-25
+25
µA
Peak value
IIV
-25
+25
µA
Peak value
Voltage Sensor Input (Asymmetrical)
Input Current Range
Oscillator
Pin VREF
Ref. Current
Ref. Voltage
Recommended crystal: TV colour burst crystal f = 3.5795 MHz
-IR
VR
45
1.1
VIH
VIL
VDD-1
50
55
1.3
µA
V
VSS+1
V
V
With R = 24kW
connected to VSS
Reference to VSS
Digital I/O
Pins SCK
High Voltage
Low Voltage
fSCK
tLO
tHI
Pins CS, DI
High Voltage
Low Voltage
VIH
VIL
Pins FMO, DO
Low Voltage
High Voltage
VOL
VOH
800
0.6
0.6
VDD-1
VDD-1
kHz
µs
µs
VSS+1
V
V
VSS+1
V
V
IOL = 5mA
IOH = -2mA
ABSOLUTE MAXIMUM RATINGS*
Parameter
Symbol
Min
Max
Unit
Supply Voltage
VDD -VSS
-0.3
6.0
V
Current on any pin
IPIN
-150
+150
mA
Storage Temperature
TSTG
-40
+125
°C
Operating Temperature
TO
-40
+85
°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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3
sames
SA9903B
PIN DESCRIPTION
PIN
Designation
20
GND
8
VDD
Positive Supply voltage. The voltage to this pin is typically +2.5V if a shunt
resistor is used for current sensing or in the case of a current transformer a
+5V supply can be applied.
14
VSS
Negative Supply Voltage. The voltage to this pin is typically -2.5V if a shunt
resistor is used for current sensing or in the case of a current transformer a
0V supply can be applied.
19
IVP
Analog Input for Voltage. The current into the A/D converter should be set at
14µARMS at nominal mains voltage. The voltage sense input saturates at an
input current of ±25µA peak.
1, 2
IIN, IIP
Inputs for current sensor. The shunt resistor voltage from each channel is
converted to a current of 16µARMS at rated conditions. The current sense input
saturates at an input current of ±25µA peak.
3
VREF
This pin provides the connection for the reference current setting resistor.
A 24kW resistor connected to VSS sets the optimum operating condition.
7
TEST
Manufacturers test pin, connect to VSS for normal operation.
10, 11
OSC1, OSC2
12
SCK
Serial clock in. This pin is used to stobe data in and out of the SA9903B
13
DO
Serial data out. Data from the SA9903B is strobed out on this pin. DO is
only driven when CS is active.
15
FMO
17
DI
Serial data in. Data is only accepted during an active chip select (CS).
18
CS
Chip select. The CS pin is active high.
4, 5, 6, 9, 16
TP4, TP5, TP6,
TP9, TP16
Analog Ground. The supply voltage to this pin should be mid-way between
VDD and VSS.
Connections for a crystal or ceramic resonator. (OSC1 = input; OSC2 = Output)
Voltage zero crossover. The FMO output generates a pulse (50% duty cycle)
on every rising edge of the mains voltage.
IIN
1
20
GND
IIP
2
19
IVP
VREF
3
18 CS
TP4
4
17 DI
TP5
Description
5
16 TP16
TP6
6
15 FMO
TEST
7
14 VSS
VDD
8
13 DO
TP9
9
12
OSC2
10
Manufacturers Test Pins. (Leave unconnected)
ORDERING INFORMATION
SCK
11 OSC1
DR-01225
Figure 2: Pin connections: Package: DIP-20, SOIC-20
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Part Number
Package
SA9903BPA
DIP-20
SA9903BSA
SOIC-20
sames
SA9903B
FUNCTIONAL DESCRIPTION
Current Sense Input (IIP and IIN)
Figure 8 shows the typical connections for the current sensor
input. The resistor R6 and R7 define the current level into the
current sense inputs of the SA9903B. At rated current the
resistor values should be selected for input currents of
16µARMS. Values for resistors R6 and R7 may be calculated as
follows:
The SA9903B is a CMOS mixed signal Analog/Digital
integrated circuit, which performs the measurement of active
power, reactive power, RMS voltage and mains frequency. The
integrated circuit includes all the required functions for singlephase power and energy measurement such as two
oversampling A/D converters for the voltage and current sense
inputs, power calculation and energy integration.
R6 = R7 = (IL / 16µA ) x RSH / 2
Where IL = Max line current
RSH = Shunt resistor or termination resistor.
The SA9903B integrates instantaneous active and reactive
power in 24 bit integrators. RMS voltage and frequency is
continuously measured and stored in respective registers. The
mains voltage zero crossover is available on the FMO output.
The voltage drop across RSH should not be less than 16mV at
rated currents. In case a current transformer is used for current
sensing the value of RSH should be less than the resistance of
the CT's secondary winding.
The SPI interface of the SA9903B has a tri-state output that
allows connection of more than one metering device on a
single SPI bus.
Voltage Sense Input (IVP)
The mains voltage is divided to 14VRMS.at nominal mains
voltage by means of resistors R1, R2, R3 and R4. The current
into the voltage sense input is set at 14µARMS with resistor R5
from the voltage divider. The voltage sense input of the AD
converter saturates at an input current of ±25µA peak.
INPUT SIGNALS
Analog Input Configuration
The input circuitry of the current and voltage sensor inputs is
illustrated in figure 3. 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 duplications
of the input currents are generated for the analog signal
processing circuitry. The current and voltage sense inputs are
identical. Both inputs are differential current driven up to ±25µA
peak. One of the voltage sense amplifier input terminals is
internally connected to GND. This is possible because the
voltage sense input is much less sensitive to externally
induced parasitic signals compared to the current sense
inputs.
Reference Voltage (VREF)
The VREF pin is the reference for the bias resistor. With a bias
resistor of 24kW optimum conditions are set. It may be varied
within ±10% for calibration purposes.
Serial Clock (SCK)
The SCK pin is used to synchronize data interchange between
the micro controller and the SA9903B. The clock signal on this
pin is generated by the micro controller and determines the
data transfer rate of the DO and DI pins.
Serial Data In (DI)
The DI pin is the serial data input pin for the SA9903B. Data will
be input at a rate determined by the Serial Clock (SCK). Data
will be accepted only during an active chip select (CS).
V DD
IIP
CURRENT
SENSOR
INPUTS
VSS
AI
VDD
Chip Select (CS)
The CS input is used to address the SA9603B. An active high
on this pin enables the SA9903B to initiate data exchange.
IIN
VSS
VDD
IVP
VOLTAGE
SENSOR
INPUT
V SS
AV
GND
DR-01288
Figure 3: Analog input internal configuration
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sames
SA9903B
OUTPUT SIGNALS
SPI - INTERFACE
SERIAL DATA OUT (DO)
DESCRIPTION
The DO pin is the serial data output pin for the SA9903B. The
Serial Clock (SCK) determines the data output rate. Data is
only transferred during on active chip select (CS). This output
is tri-state when CS is low.
A serial peripheral interface bus (SPI) is a synchronous bus
used for data transfers between a micro controller and the
SA9903B. The pins DO (Serial Data Out), DI (Serial Data In),
CS (Chip Select), and SCK (Serial Clock) are used in the bus
implementation. The SA9903B is the slave device with the
micro controller the bus master. The CS input initiates and
terminates data transfers. A SCK signal (generated by the
micro controller) strobes data between the micro-controller
and the SCK pin of the SA9903B device. The DI and DO pins
are the serial data input and output pins for the SA9903B,
respectively.
MAINS VOLTAGE SENSE ZERO CROSSOVER
(FMO)
The FMO output generates a signal, which follows the mains
voltage zero crossings, see figure 4. The micro controller may
use the FMO to extract mains timing.
ELECTROSTATIC DISCHARGE (ESD) PROTECTION
The SA9903B Integrated Circuit's inputs/outputs are protected
against ESD.
REGISTER ACCESS
The SA9903B contains four 24 bit registers. The content
represents active energy, reactive energy, mains voltage and
mains frequency. The register addresses are shown in the
following table:
POWER CONSUMPTION
The power consumption rating of the SA9903B integrated
circuit is less than 25mW.
Header
A5 A4 A3 A2 A1 A0
bits
ID
Register
1
Active
1
1
0
X
X
0
0
0
0
2
Reactive
1
1
0
X
X
0
0
0
1
3
Voltage
1
1
0
X
X
0
0
1
0
4
Frequency
1
1
0
X
X
0
0
1
1
Voltage
+5V (VDD)
FM0
0V (VSS)
Dr-01498
Figure 4: Mains voltage zero corssover pin FMO
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sames
SA9903B
The sequence 110 (0x06) must precede the 6-bit address of
the register being accessed. When CS is HIGH, data on pin DI
is clocked into the SA9903B on the rising edge of SCK. Figure
5 shows the data clocked into DI comprising of 1 1 0 A5 A4 A3
A2 A1 A0.
SCK
t3
t4
DI
Address locations A5 and A4 are included for compatibility with
future developments.
t2
t5
DO
Registers may be read individually and in any order. After a
register has been read, the contents of the next register value
will be shifted out on the DO pin with every SCK clock cycle.
Data output on DO will continue until CS is inactive.
t1
CS
DR-01545
The 9 bits needed for register addressing can be padded with
leading zeros when the micro-controller requires a 8 bit SPI
word length. The following sequence is valid:
0000 0001 10A5A4
Parameter Description
A3A2A1A0
Min
Max
t1
SCK rising edge to DO valid
625ns 1.160µs
DATA FORMAT
t3
SCK min high time
625ns
Figure 5 shows the SPI waveforms. After the least significant
digit of the address has been entered on the rising edge of
SCK, the output DO goes low with the falling edge of SCK.
Each subsequent falling edge transition on the SCK pin will
validate the next data bit on the DO pin.
t4
SCK min low time
625ns
t2
Setup time for DI and CS
before the rising edge of SCK 20ns
t5
The content of each register consists of 24 bits of data. The
MSB is shifted out first.
DI hold time
625ns
Figure 6: SPI Timing diagrams with timing information
SCK
CS
Read command
DI
1
1
Register address
0
A5
A4
A3
A2
A1
A0
Register Data
DO
0
D23
D22
Next data register
D21
Figure 5: SPI waveforms
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D1
D0
D23
D22
D1
D0
High impedance
sames
SA9903B
ACTIVE AND REACTIVE REGISTER VALUES
USING THE REGISTER VALUES
The active and reactive registers are 24 bit up/down counters,
that increment or decrement at a rate of 320k samples per
second at rated conditions. The register values will increment
for positive energy flow and decrement for negative energy
flow as indicated in figure 7. The active and reactive 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. The data read from the registers
represents the active or reactive power integrated over time.
The increase or decrease between readings represent the
measured energy consumption.
ACTIVE ENERGY REGISTER
The active energy measured by the SA9903B is
calculated as follows:
Energy = VRATED x IRATED x N / INTTIME / 320000
VRATED
Rated mains voltage of meter
IRATED
Rated mains current of meter
N
Difference in register values between
successive reads (delta value)
INTTIME Time difference between successive register
reads (in seconds)
Register wrap around
REACTIVE ENERGY REGISTER
The reactive energy measured by the SA9903B is
calculated as follows:
Positive energy flow
Register values
0
H7FFFFF
................ (8388607)
H800000
(8388608)
Reactive = VRATED x IRATED x N / INTTIME / 320000
VRATED
Rated mains voltage of meter
IRATED
Rated mains current of meter
N
Difference in register values between
successive reads (delta value)
INTTIME Time difference between successive register
reads (in seconds)
HFFFFFF
................ (16777215)
Negative energy flow
Register wrap around
DR-01590
Figure 7: Register increment / decrement showing the
register wrap around
MAINS VOLTAGE REGISTER
At rated conditions, the active and reactive registers will wrap
around every 52 seconds. The micro controller program needs
to take this condition into account when calculating the
difference between register values.
The RMS voltage measurement is accurate to 1% in a
range of 50% to 115% of rated mains voltage. The RMS
mains voltage measured by the SA9903B is calculated as
follows:
As an example lets assume that with a constant load
connected, the delta value (delta value = present register previous / register 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 period between reads). However this will not be
true when a wrap around occurs, as the following example will
demonstrate:
Description
Present register value
Valiable Decimal
MAINS FREQUENCY REGISTER
Bits D0 to D9 represents a counter value that is scaleable
to the mains frequency measured.
The mains frequency measured by the SA9903B is
calculated as follows:
Hex
new_val 16767215 0x00FFD8EF
Previous register value old_val
new_val - old_val =
Voltage = VRATED x VREGISTER VALUE / 700
VRATED
Rated mains voltage of meter
VREGISTER VALUE
Voltage register value
delta_val
Frequency = FCRYSTAL / 256 / FREGISTER VALUE
FCRYSTAL
The external crystal frequency.
FREGISTER VALUE Bits D9 to D0 of the frequency register.
16744955 0x00FF81FB
22260 0x000056F4
The register now wraps around so after the next read
Bits D10 to D22 are not used in the frequency register.
Bit D23 is set with the same status as the FMO output.
the values are as follows:
Present register value
new_val
Previous register value old_val
new_val - old_val =
12260 0x00002FE4
16767215 0x00FFD8EF
delta_val -16754955 0x00FFA90B
Computing this delta value will result in incorrect calculations.
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sames
SA9903B
TYPICAL APPLICATION
VOLTAGE DIVIDER
In figure 8, the components required for a two wire single phase
power/energy metering section of a meter, is shown The
application uses a shunt for the mains current sensing. The
metering section described in this section will be designed for
measuring 230V/80A with precision better than Class 1
The voltage divider is calculated for a voltage drop of
14V+2.3% (14.33V). Equations for the voltage divider in figure
8 are:
The most important external components for the SA9903B
integrated circuit are the current sense resistors, the voltage
sense resistors as well as the bias setting resistor. The
resistors used in the metering section should be of the same
type so temperature effects are minimized.
BAIS RESISTOR
R8 defines all on-chip and reference currents. With R8=24kW,
optimum conditions are set. The meter calibration is
implemented in software.
SHUNT RESISTOR
The voltage drop across the shunt resistor (RSH) at rated
current should be at least 20mV. A shunt resistor of 625µW is
chosen. The voltage drop across the shunt resistor is 50mV at
rated conditions (Imax for the meter).
CURRENT SENSE RESISTORS
The resistors R6 and R7 define the current level into the current
sense inputs of the device. The resistor values are selected for
an input current of 16µA on the current inputs at rated
conditions.
RA = R1 + R2 + R3
RB = R4 || R5
Combining the two equations gives:
( RA + RB ) / 230V = RB / 14.33V
Values are chosen for R4 = 24kW and R5 =1MW. Substituting
the values result in:
RB = 23.4375kW
RA = RB ( 230V / 14.33V - 1 )
RA = 352.7kW.
Resistor values of R1, R2 and R3 are chosen to be 110kW,
110kW and 130kW.
CRYSTAL OSCILLATOR
A color burst TV crystal with f = 3.5795MHz is used for the
oscillator. The oscillator frequency is divided down to
1.7897MHz on-chip, to supply the A/D converters as well as
the digital circuitry.
According to equation described in the Current Sense inputs
section:
R6 = R7 = (IL / 16µA) x RSH / 2
= 80A / 16µA x 625µW / 2
=1.5625kW
A resistor value of 1.6k is chosen, the -2.3% deviation from the
calculated value will be compensated for when calculating the
resistor values for the voltage path.
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Figure 8: Typical application circuit
9/12
LIVE
NEUTRAL
LIVE
NEUTRAL
RSH
R9
-2V5
C6
+2V5
R1
C5
R8
R7
R6
R2
D2
D1
10
9
8
7
6
5
4
3
2
1
SA9903B
X1
OSCO
TP9
VDD
TEST
TP2
TP3
TP4
VREF
IIP
IIN
U1
R3
R11
+ C4
+ C3
R10
OSCI
DI
DO
VSS
FMO
TP16
DI
CS
IVP
GND
dr-01589
11
12
13
14
15
16
17
18
19
20
D4
D3
-2V5
R5
-2V5
C1
C2
+2V5
R4
GND
SCK
SDO
FMO
SDI
CS
SA9903B
sames
sames
SA9903B
Parts List for Application Circuit: Figure 8
Symbol
Description
U1
R1
R2
R3
R4
R5
R6
R7
R8
R9
R10
R11
RSH
C1
SA9903B
Resistor, 110k, 1/4W, 1% metal
Resistor, 110k, 1/4W, 1% metal
Resistor, 130k, 1/4W, 1% metal
Resistor, 24k, 1/4W, 1% metal
Resistor, 1M, 1/4W, 1% metal
Resistor, 1.6k, 1/4W, 1% metal
Resistor, 1.6k, 1/4W, 1%, metal
Resistor, 24K, 1/4W, 1%, metal
Resistor, 47R, 2W, 5%, wire wound
Resistor, 680R, 1/4W, 1%, metal
Resistor, 680R, 1/4W, 1%, metal
Shunt Resistor, 80A/50mV
Capacitor, 220nF, ceramic
C2
C3
C4
C5
C6
D1
D2
Capacitor, 220nF, ceramic
Capacitor, 220uF, 16V, electrolytic
Capacitor, 220uF, 16V, electrolytic
D3
D4
X1
Capacitor, 470nF, 250VAC, polyester
Capacitor, 820nF, ceramic
Diode, 1N4003
Diode, 1N4003
Diode, Zener, 2.5V
Diode, Zener, 2.5V
Crystal, 3.579545MHz
Note 1: Capacitor C6 to be positioned as close as possible to supply pins VDD and VSS of U1 as possible.
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Detail
DIP-20/SOIC-20
Note 1
sames
SA9903B
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sames
PM9607AP
SA9903B
DISCLAIMER:
The information contained in this document is confidential and proprietary to South African Micro-Electronic 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 address below:
[email protected]
For the latest updates on datasheets, please visit our web site:
http://www.sames.co.za.
SOUTH AFRICAN MICRO-ELECTRONIC SYSTEMS
DIVISION OF LABAT TECHNOLOGIES (PTY) LTD
Tel: (012) 333-6021
Tel: Int +27 12 333-6021
Fax: (012) 333-8071
Fax: Int +27 12 333-8071
33 ELAND STREET
KOEDOESPOORT INDUSTRIAL AREA
PRETORIA
REPUBLIC OF SOUTH AFRICA
P O BOX 15888
33 ELAND STREET
LYNN EAST 0039
REPUBLIC OF SOUTH AFRICA
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