sames
SA9103C
SINGLE PHASE BIDIRECTIONAL POWER/ENERGY
METERING IC WITH SERIAL INTERFACE
FEATURES
n
Performs bidirectional active and
reactive power/energy, frequency and
voltage measurement
n
Meets the IEC 521/1036 Specification
requirements for Class 1 AC Watt hour
meters
n
Protected against ESD
n
Total power consumption rating below
25mW
n
Adaptable to different current sensor
technologies
n
Operates over a wide temperature
range
n
Serial interface having a RS232 protocol
n
Precision voltage reference on-chip
Tri-state output to allow parallel
connection of devices
n
DESCRIPTION
The SAMES SA9103C bidirectional Single
Phase Power/Energy metering integrated
circuit has a serial interface with a RS232
protocol, ideal for use with a µ-Controller.
The SA9103C performs the calculation for
active and reactive power.
The integrated values for active and
reactive energy as well as the mains
frequency and voltage information are
accessable through the RS232-Interface
as 16 bit values.
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 SA9103C integrated circuit is available
in both 20 pin dual-in-line plastic (DIP-20),
as well as 20 pin small outline (SOIC-20)
package types.
PIN CONNECTIONS
IIN
1
20
IIP
2
19
IVP
VREF
3
18
CON
CPON
4
17
COP
CPOP
5
16
CIN
CPIN
6
15
CPIP
V DD
7
14
CIP
V SS
8
13
SIN
TP9
9
12
SOUT
OSC2
10
11
OSC1
GND
DR-00829
Package: DIP-20
SOIC-20
1/16
4259
PDS039-SA9103C-001
REV. D
23-08-1996
SA9103C
BLOCK DIAGRAM
V DD
IIP
ACTIVE
ENERGY
IIN
REACTIVE
ENERGY
ANALOG
V SS
SIN
SOUT
SERIAL
FREQUENCY
INTERFACE
SIGNAL
VOLTAGE
PROCEVOLTAGE
REF.
SSING
IVP
GND
OSC
VREF
DR-00830
OSC1
TIMING
OSC2
ABSOLUTE MAXIMUM RATINGS*
Parameter
Supply Voltage
Symbol
VDD -VSS
Min
-0.3
Max
6.0
Current on any pin
IPIN
-150
+150
mA
Storage Temperature
TSTG
-40
+125
°C
TO
-10
+70
°C
Operating Temperature
Unit
V
* 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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SA9103C
ELECTRICAL CHARACTERISTICS
(VDD = 2.5V, VSS = -2.5V, over the temperature range -10°C to +70°C#, unless otherwise
specified.)
Parameter
Symbol Min
Typ
Max
Unit Condition
Supply Voltage: Positive
VDD
2.25
2.75
V
Supply Voltage: Negative
VSS
-2.75
-2.25
V
Supply Current: Positive
IDD
5
6
mA
Supply Current: Negative
ISS
5
6
mA
-25
+25
µA
Peak value
IIV
-25
+25
µA
Peak value
Pin SOUT
Output Low Voltage
Output High Voltage
VOL
VOH
VSS+1
VDD-1
V
V
IOL = 5mA
IOH = -2mA
Pin SIN
Input High Voltage
Input Low Voltage
Pull-up Current
VIH
VIL
-II
V
V
µA
VIN = VSS
Current Sensor Inputs (Differential)
Input Current Range
I II
Voltage Sensor Input (Asymetrical)
Input Current Range
Oscillator
VSS+1
150
50
Recommended crystal:
TV colour burst crystal f = 3.5795 MHz
Pin VREF
Ref. Current
Ref. Voltage
#
VDD-1
-IR
VR
45
1.1
50
55
1.3
µA
V
With R = 24kΩ
connected to VSS
Referred to VSS
Extended Operating Temperature Range available on request.
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SA9103C
PIN DESCRIPTION
Pin
Designation
Description
20
8
GND
VDD
Ground
Positive Supply Voltage
14
VSS
Negative Supply Voltage
19
IVP
Analog input for Voltage
1
IIN
Inputs for current sensor
2
IIP
11
OSC1
Connections for crystal or ceramic resonator
10
OSC2
(OSC1 = Input ; OSC2 = Output)
12
SOUT
Serial Interface Out
13
SIN
Serial Interface In
4
CPON
Connections for outer loop capacitors of
5
CPOP
A/D converter (Voltage)
6
CPIN
Connections for inner loop capacitors of
7
CPIP
A/D converter (Voltage)
15
CIP
Connections for inner loop capacitors of
16
CIN
A/D converter (Current)
17
COP
Connections for outer loop capacitors of
18
CON
A/D converter (Current)
3
VREF
Connection for current setting resistor
9
TP9
Test Pin. Must be connected to VSS
FUNCTIONAL DESCRIPTION
The SA9103C is a CMOS mixed signal Analog/Digital integrated circuit, which performs
power/energy calculations across a power range of 1000:1, to an overall accurancy of
better than Class 1.
The integrated circuit includes all the required functions for 1-phase power and energy
measurement, such as two oversampling A/D converters for the voltage and current
sense inputs, power calculation and energy integration. Internal offsets are eliminated
through the use of cancellation procedures. The SA9103C integrates the measured
active and reactive power consumption into 22 bit integrators, which are accessable via
a serial port having a RS232 protocol. Two additional on-chip registers exist: one register
contains the mains frequency information; and the other the voltage information.
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SA9103C
1.
Power calculation
In the Application Circuit (Figure 1), the voltage drop across the shunt will be
between 0 and 16mV (0 to 80A through a shunt resistor of 200µΩ). This voltage is
converted to a current of between 0 and 16µA, by means of resistors R 1 and R2.
The current sense input saturates at an input current of ±25µA peak.
For the voltage sensor input, the mains voltage (230V AC) is divided down through
a divider to 14V. The resulting current into the A/D converter input is 14µA at
nominal voltage, via resistor R4 (1MΩ).
In this configuration, with a mains voltage of 230V and a current of 80A, the
SA9103C functions at its optimum conditions, having a margin of 3dB for overload
available.
2.
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 duplications of the input currents are generated
for the analog signal processing circuitry.
V DD
IIP
CURRENT
SENSOR
INPUTS
V SS
AI
V DD
IIN
V SS
V DD
IVP
VOLTAGE
SENSOR
INPUT
DR-00831
sames
V SS
AV
GND
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SA9103C
3.
Electrostatic Discharge (ESD) Protection
The SA9103C integrated circuit's inputs/outputs are protected against ESD .
4.
Power Consumption
The power consumption rating of the SA9103C integrated circuit is less than 25mW.
5.
Serial Interface
Reading and resetting of the SA9103C's on-chip integrators, is performed via the
serial interface.
The settings are:
19 200 Baud
1 Start bit (S)
1 Stop bit (E)
No parity bits
The serial interface, with RS232 protocol, has been designed to operate directly with
a PC (Personal Computer).
The serial interface allows for the following operations:
Read Integrator (RD): The SA9103C integrated circuit transmits the integrator
status to the controller, after the current measurement cycle has been completed
(8 mains periods maximum).
The register containing the mains frequency information is read only.
Reset Integrator (RES): The SA9103C integrator is reset, without transmitting the
integrator status.
Read/Reset Integrator (RD/RES): The SA9103C transmits the integrator status
and resets the integrator after the current measurement cycle has been completed.
In a typical application, the system controller monitors the status of the SA9103C's
integrator using the "Read" command. At rated load conditions, the capacity of the
22 bit integrator allows for an integration time of 2 seconds prior to integrator
overflow.
If after a "Read" command, the integrator value is sufficently high, a "Read/Reset"
command from the controller causes the SA9103C integrated circuit to complete the
existing measurement cycle, transmit the 16 most significant bits of the 22 bit
integrator via the Serial Output (SOUT) to the controller and restart the integrator.
In order to ensure correct measurements, the integrator commands ("Read" and
"Read/Reset") are only executed after completion of the internal offset calibration
cycle. The cycle length is 8 mains periods.
Thus, for power calculations, the time value should be taken from the difference in
time from the previously received energy value to the currently received value.
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SA9103C
By adapting the "Read/Reset" rate to the line current the accuracy of the measurement
can be achieved down to lowest signal levels.
Read, Reset and Read/Reset of integrator for active energy
RD
RD
RES
RES
RD
RD/
RES
RES
STOP
BIT
START
BIT
DR-00832
Read, Reset and Read/Reset of integrator for reactive energy
RD
RD
RES
RES
RD
RD/
RES
RES
START
BIT
STOP
BIT
DR-00833
Read frequency register
RD
RD
DR-00834
START
BIT
STOP
BIT
Read, Reset and Read/Reset of integrator for voltage
RD
RD
RES
RES
RD
RD/
RES
DR-01152
START
BIT
sames
RES
STOP
BIT
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SA9103C
The register access codes which can be written to the SA9103C via the serial
communications port are shown in the table below.
REGISTER
ACTIVE
RE-ACTIVE
VOLTAGE
FREQUENCY
READ
$01
$81
$C1
$41
RESET
$02
$82
$C2
-
READ-RESET
$03
$83
$C3
-
Data on SOUT
8
9
10
11
12
13
FIRST BYTE
14
15
0
1
2
3
4
5
6
7
SECOND BYTE
DR-00835
From the two bytes of data output by the device, the value for the register can
be derived as shown:
Register value =
(First Byte * 256) + Second Byte
The most significant bit of the 16 bit energy register (active or reactive) is an
indication of the direction of the energy flow (0 = positive, 1 = negative).
6.
Register Values
a.
The active and reactive energy measured per count, may be calculated by
applying the following formula:
V*I
Energy per Count
=
K Watt seconds
Where
V
I
K
=
=
=
Rated Voltage
Rated Current
9281
for Active Energy
9281 * 2 for Reactive Energy
π
b.
The mains frequency may be calculated as follows:
Crystal frequency
Frequency =
Register Value * 8
c.
To calculate the measured voltage, the following formula may be used:
V*n
Vmeasured = 14000
*t
Where
8/16
V
t
n
sames
=
=
=
rated voltage
time difference between successive reads
difference in register values between
successive reads
SA9103C
7.
Software flow
In an application in which all the registers must be accessed, the software loop
illustrated below can be implemented.
READ FREQUENCY COMMAND
DELAY OF 8 MAINS PERIODS
RECEIVE FREQUENCY
READ ACTIVE COMMAND
LOOP
DELAY OF 8 MAINS PERIODS
∧
RECEIVE ACTIVE
READ REACTIVE COMMAND
DELAY OF 8 MAINS PERIODS
RECEIVE REACTIVE
READ VOLTAGE COMMAND
DELAY OF 8 MAINS PERIODS
RECEIVE VOLTAGE
The SA9103C integrated circuit transmits the register values only after completion
of the current measurement cycle (8 mains periods maximum).
The delay of 8 mains periods can be calculated from the period value of the
frequency returned by the initial read, and updated with each subsequent reading
of frequency.
Each successive read of the registers takes place regularly at intervals of 4 blocks
of 8 mains cycles. This time and the difference between successive energy register
values can be used to calculate power.
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9/16
SA9103C
8.
Calibration
For the calibration of the SA9103C, the following procedure is recommended:
a. Establish calibration factor for active energy (Ka) at pf close to 1.
Active (Measured) = register_value (Active) * Ka.
1
b. The factor for reactive (Kr) is typically Ka * PI/2.
For higher accuracy of Kr, establish Kr at pf close to 0.
Reactive (Measured) = register_value (Reactive) * Kr
2
c. At pf close to 1, establish error for reactive (Er)
Er = (Reactive (Measured) - Reactive (True)) / Active (Measured)
3
Reactive (Corrected) = Reactive (Measured) - Er * Active (Measured)
3b
Measurement
Having determined the scaling factors (Ka & Kr) and error correction constant (Er)
the measurement cycle consists of the following steps:
step 1
Read active register
step 2
∨
Calculate Active (Measured) as per 1
step 3
∨
Read reactive register
step 4
∨
Calculate Reactive (Measured) as per 2
step 5
∨
Perform error correction
Calculate Reactive (Corrected) as per 3b
⇒
Active energy
⇒
Reactive energy
The above five steps must be performed for each measurement cycle.
10/16
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SA9103C
TYPICAL APPLICATIONS
In the Application Circuits (Figures 1 and 2), the components required for power metering
applications, are shown.
In Figure 1 a shunt resistor is used for current sensing. In this application, the circuitry
requires a +2.5V, 0V, -2.5V DC supply.
In the case of Figure 2, when using a current transformer for current sensing, a +5V, 0V
DC supply is sufficient for the circuit.
The most important external components for the SA9103C integrated circuit are:
C1 and C2 are the outer loop capacitors for the two integrated oversampling A/D
converters. The value of these capacitors is 560pF. The actual values determine the
signal to noise and stability performance. The tolerances should be within ±10%.
C3 and C4 are the inner loop capacitors of the A/D converters. The optimum value is 3.3nF.
The actual values are uncritical. Values smaller than 0.5nF and larger than 5nF should
be avoided.
R1, R2 and RSH are the resistors defining the current level into the current sense input.
The values should be selected for an input current of 16µA into the SA9103C at rated line
current.
Values for RSH of less than 200µΩ should be avoided.
R1 = R2 = (IL/16µA) * RSH/2
Where IL
= Line current
RSH = Shunt resistor/termination resistor
R3, R6 and R4 set the current for the voltage sense input. The values should be selected
so that the input current into the voltage sense input (virtual ground) is set to 14µA.
R7 defines all on-chip bias and reference currents. With R7 = 24kΩ, optimum conditions
are set.
XTAL is a colour burst TV crystal (f = 3.5795MHz) for the oscillator. The oscillator
frequency is divided down to 1.7897MHz on-chip to supply the A/D converters and digital
circuitry.
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11/16
SA9103C
Figure 1: Application Circuit using a Shunt Resistor for Current Sensing, having
a PC (Personal Computer) Interface.
12/16
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SA9103C
Part 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
33
34
35
36
Symbol
IC-1
IC-2
IC-3
D1
D2
D3
ZD1
ZD2
XTAL
R1
R2
R3
R4
R5
R6
R7
R8
R9
R10
R11
R12
R13
R14
R15
C1
C2
C3
C4
C9
C10
C11
C12
C13
C14
C15
RSH
Description
SA9103C
Opto Coupler 4N35
Opto Coupler 4N35
Diode, Silicon, 1N4148
Diode, Silicon, 1N4148
Diode, Silicon, 1N4148
Diode, Zener, 2.4V, 200mW
Diode, Zener, 2.4V, 200mW
Crystal, 3.5795MHz
Resistor, 1% metal
Resistor, 1% metal
Resistor, 390k, (230VAC), 1% metal
Resistor, 1M, 1/4W, 1% metal
Resitor, 470Ω, 2W, 5%, carbon
Resistor, 24k, 1/4W, 1%, metal
Resistor, 24k, 1/4W, 1%, metal
Resistor, 680Ω, 1/4W, 5%
Resistor, 680Ω, 1/4W, 5%
Resistor, 680Ω, 1/4W, 5%
Resistor, 100k, 1/4W, 5%
Resistor, 120Ω, 1/4W, 5%
Resistor, 120k, 1/4W, 5%
Resistor, 3.9k, 1/4W, 5%
Resistor, 120Ω, 1/4W, 5%
Capacitor, 560pF
Capacitor, 560pF
Capacitor, 3.3nF
Capacitor, 3.3nF
Capacitor, 100nF
Capacitor, 100nF
Capacitor, 0.47µF, 250VAC, polyester
Capacitor, 100nF
Capacitor, 100µF
Capacitor, 100µF
Capacitor, 820nF
Shunt Resistor
Detail
DIP-20/SOIC-20
DIP-6
DIP-6
Colour burst TV
Note 1
Note 1
Note 2
Note 1: Resistor (R1 and R2) values are dependant upon the selected value of RSH.
Note 2: See TYPICAL APPLICATIONS when selecting the value for RSH.
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SA9103C
Figure 2: Application Circuit using a Current Transformer for Current Sensing.
14/16
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SA9103C
Parts List for Application Circuit: Figure 2
Item
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
Note 1:
Note 2:
Note 3:
Note 4:
Symbol
IC-1
XTAL
RSH
R1
R2
R3
R4
R6
R7
R8
R9
C1
C2
C3
C4
C9
C10
C11
CT
Description
SA9103C
Crystal, 3.5795MHz
Resistor
Resistor, 1%, metal
Resistor, 1%, metal
Resistor, 390k, (230VAC) 1%, metal
Resistor, 1M, 1/4W, metal
Resistor, 24k, 1/4W, metal
Resistor, 24k, 1/4W, metal
Resistor, 2.2k, 1/4W, 5%
Resistor, 2.2k, 1/4W, 5%
Capacitor, 560pF
Capacitor, 560pF
Capacitor, 3.3nF
Capacitor, 3.3nF,
Capacitor, 820nF
Capacitor, 100nF
Capacitor
Current Transformer
Detail
DIP-20/SOIC-20
Colour burst TV
Note 1
Note 2
Note 2
Note 3
Note 4
See TYPICAL APPLICATIONS when selecting the value of RSH.
Resistor (R1and R2) values are dependant upon the selected value of
RSH.
Capacitor (C9) to be positioned as close to IC-1, as possible.
Capacitor (C11) selected for DC blocking and to minimize phase error
introduced by the current transformer.
Part Number
Package
SA9103CPA
SA9103CSA
DIP-20
SOIC-20
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SA9103C
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 address below:
[email protected]
For the latest updates on datasheets, please visit out 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:
16/16
012 333-6021
012 333-8071
sames
Tel:
Fax:
Int +27 12 333-6021
Int +27 12 333-8071