Single Phase Kilowatt-hour Metering IC for
Mechanical Display Applications
Sames
SA2002D
FEATURES
+ Provides a single chip solution for energy meters having a
+
+
+
+
+
mechanical display
+
+
+
+
No external crystal or resonator required
Direct stepper motor / impulse counter drive
Unidirectional and bi-directional energy measurement
Configurable for different meter ratings
Adaptable to different types of current sensors
Precision voltage reference on chip
Operates over a wide temperature range
Low power consumption
Meets the IEC 521/1036 Specification requirements for
Class 1 AC Watt hour meters
DESCRIPTION
The SAMES SA2002D provides a single chip solution for
single phase energy meters. Very few external components
are required and it has direct drive capability for
electromechanical counters. The SA2002D does not required
an external crystal. A precision oscillator, which is supplies the
circuitry with a stable frequency, is integrated on chip.
The SA2002D can be configured for positive, negative or bidirectional energy measurement.
The SA2002D Single Phase kWh metering integrated circuit
generates a pulse rate output, the frequency of which is
proportional to the power consumption. The SA2002D
performs the calculation for active power. The method of
calculation takes the power factor into account.
Programmable inputs allow the meter manufacturer to
configure the SA2002D for different meter ratings without
having to change the stepper motor or impulse counter gear
ratio. A high frequency pulse output is available at the LED
output for meter calibration purposes. The SA2002D includes
an anti-creep feature.
The SA2002D integrated circuit is available in 20 pin dual-inline plastic (PDIP20), as well as 20 pin small outline (SOIC20)
package types.
DIRI DIROFAST
VDD
IIP
IIN
ANALOG
SIGNAL
PROCESSING
POWER
INTEGRATOR
LEDPULSE
LED
IVP
AGND
OSC TIMING
MOP
COUNTER
DRIVER
MON
REFERENCE
&
BIAS
Dr-01566
VREF
VSS CNF
R0 R1 R2
Figure 1: Block diagram
SPEC-0024 (REV. 4)
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SA2002D
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
2.5
3.6
5
mA
Supply Current: Negative
ISS
2.5
3.6
5
mA
II I
-25
+25
µA
Peak value
II V
-25
+25
µA
Peak value
-IR
VR
45
1.1
55
1.3
µA
V
With R = 24kW
connected to VSS
Reference to VSS
Pin R0, R1, R2, DIRI, CNF
Input High Voltage
Input Low Voltage
VI H
VI L
VDD-1
VSS+1
V
V
Pin MOP, MON, LED, DIRO
Output High Voltage
Output Low Voltage
VOH
VOL
VDD-1
VSS+1
V
V
Parameter
Condition
Current Sensor Inputs (Differential)
Input Current Range
Voltage Sensor Input (Asymmetrical)
Input Current Range
Pin VREF
Ref. Current
Ref. Voltage
50
Digital I/O
#Extended Operating Temperature Range available on request.
ABSOLUTE MAXIMUM RATINGS*
Parameter
Symbol
Min
Max
Unit
Supply Voltage
VDD -VSS
3.2
6.0
V
Current on any pin
IPI N
-150
+150
mA
Storage Temperature
TSTG
-40
+125
°C
Operating Temperature
TO
-25
+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
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SA2002D
PIN DESCRIPTION
Description
PIN
Designation
20
AGND
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
3
VREF
6, 5, 4
R0, R1, R2
7
FAST
FAST calibration. The LED pulse rate change to 1252Hz at rated conditions if FAST is
connected to VDD.
9
CNF
Configure / Test input. For normal operation this pin must be connected to VSS.
12, 15
MON, MOP
13
LED
Calibration LED output. Refer to the rated condition select section of the pulse rate output
options.
17
DIRO
Direction output. This output indicates the energy flow direction.
18
DIRI
Direction input. This input is used to enable either bi-directional or unidirectional
energy measurement.
10,11,16
NC
No Connection
Analog Ground. The supply voltage to this pin should be mid-way between VDD and VSS.
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.
This pin provides the connection for the reference current setting resistor. A 24kW resistor
connected to VSS sets the optimum operating condition.
Rated Condition Select. These inputs are used for the different rated condition configuration,
including the LED frequency calibration pulse.
Motor pulse outputs. These outputs can drive an electromechanical counter directly.
ORDERING INFORMATION
IIN
1
20
AGND
Part Number
Package
IIP
2
19
IVP
SA2002DPA
PDIP20
VREF
3
18 DIRI
SA2002DSA
SOIC20
R2
4
17 DIRO
R1
5
16 NC
SA2002D
R0
6
15 MON
FAST
7
14 VSS
VDD
8
13
LED
CNF
9
12
MOP
NC
11 NC
10
DR-01567
Figure 2: Pin connections: Package: PDIP20, SOIC20
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sames
SA2002D
FUNCTIONAL DESCRIPTION
The SA2002D is a CMOS mixed signal Analog/Digital
integrated circuit, which performs power/energy calculations
across a power range of 1000:1, to an overall accuracy of
better than Class 1.
divided down through a divider (R3, R4 and P1) to 14VRMS. The
current into the A/D converter input is set at 14µARMS at nominal
mains voltage, via resistor R5 (1MW). P1 may be varied for
calibration purposes.
The integrated circuit includes all the required functions for 1phase 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 SA2002D generates pulses, the frequency of
which is proportional to the power consumption. A
complementary output (MOP and MON) is provided for the
stepper motor. One energy pulse is represented by MOP pulse
and subsequently followed by a MON pulse. This configuration
avoids the possibility that, after power up, the first energy pulse
is lost due to the stepper motor being in the wrong phase. The
pulse rate on these pins follow the instantaneous active power
consumption. The LED pulse output follows the average power
consumption measured and is intended for calibration
proposes.
The pulse rate available at the motor drive pins MOP and MON
(counter resolution) is fixed at 100 (200) impulses/kWh*. The
frequency of the LED pin is dependant on the settings of pins
R0, R1 and R2, which allow a selection of different rated
conditions. In this case (R0, R1 and R2 set to logic 0) the LED
output is 6400 impulses/kWh, with the rated conditions set to
220V/10A. This facility allows meter manufacturers to cater for
a wide range of metering applications with minimal design
changes.
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.
POWER CALCULATION
In the Application Circuit (Figure 3), the voltage drops across
the shunt will be between 0 and 16mVRMS (0 to 80A through a
shunt resistor of 200µW). The voltage is converted to a current
of between 0 and 16mVRMS, by means of resistors R1 and R2.
The current sense input saturates at an input current of ±25µA
peak.
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
For the voltage sensor input, the mains voltage (230VAC) is
CURRENT
SENSOR
INPUTS
VSS
AI
VDD
VDD
N
Supply
L
IIN
VDD
Supply
REVERSE
VSS
PULSES
VDD
VDD
DIRO DIRI
IVP
R1
IIN
VOLTAGE
SENSOR
INPUT
LED
IIP
R2
R3
V SS
AV
R5
IVP
SA2002
8 8 8 8 8 8 8
AGND
R4
GND
P1
DR-01288
MOP
MON
VREF
DR-01568
Figure 4: Analog Input Internal Configuration
VSS TEST R0 R1 R2
*The figure not in parenthesis indicates that a MOP pulse
followed by a MON pulse is treated as one energy pulse. The
figure inside parenthesis means that a MOP pulse followed by
a MON pulse is treated as two energy pulses.
L
LOAD
N
Figure 3: Application Circuit
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sames
SA2002D
The current and voltage sense inputs are both identical. Both
inputs are differential current driven up to ±25µA peak. One
input of the voltage sense amplifier 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.
Rated condition select (R0, R1, R2)
The rated condition select pins R0, R1 and R2 are inputs,
which configure the SA2002D for different rated conditions.
This feature eliminates the need for different stepper motor
gear ratios. The LED pulse output follows the average power
consumption measured.
R2 R1 R0
ELECTROSTATIC DISCHARGE (ESD)
PROTECTION
The SA2002D integrated circuit's inputs/outputs are protected
against ESD.
0
0
0
0
1
1
1
1
POWER CONSUMPTION
The power consumption rating of the SA2002D integrated
circuit is less than 25mW.
INPUT SIGNALS
VREF
A bias resistor of 24kW sets optimum bias and reference
conditions on chip. Calibration of the SA2002D should be done
on the voltage input as described in Typical Applications.
6400
3200
1600
800
6400
3200
1600
Test Mode
100 (200)
100 (200)
100 (200)
100 (200)
100 (200)
100 (200)
100 (200)
-
The Motor pulse rate is not restricted to 100 (200) pulses/kWh.
The following examples show how different LED and motor
pulse rates can be achieved:
Example 1. A manufacturer designing a 220V/10A meter can
choose to have the pins R2, R1 and R0 connected as for a
220V/20A (R2=0, R1=0 and R0=1). In comparison to table 1
the Rated Condition is now half (2200W), this in turn doubles
the LED and Motor Pulse output rates as shown in the
following table:
R1 = R2 = (IL/16µA) x RSH/2
Where IL
=
Line current
RSH
=
Shunt resistor or termination
Resistor if a CT is used as the current sensor.
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220V/10A
220V/20A
220V/40A
220V/80A
220V/6A
220V/30A
220V/60A
Test Mode
Motor Pulse
Rate (Pulses/
KWh)*
*This figure not in parenthesis indicates that a MOP pulse
followed by a MON pulse is treated as one energy pulse. The
figure inside parenthesis means that a MOP pulse followed by
a MON pulse is treated as two energy pulses.
The values for resistors R1 and R2 can be calculated as
follows:
Voltage Sense Input (IVP)
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. Referring to Figure 3 the
typical connections for the voltage sense input is illustrated.
Resistors R3, R4 and R5 set the current for the voltage sense
input. The mains voltage is divided down to 14VRMS. The current
into the A/D converter input is set at 14µARMS via resistor R5.
0
1
0
1
0
1
0
1
LED Output
(Pulses/
KWh)
Table 1
Current sense input (IIP and IIN)
Figure 3 on page 4 shows the typical connections for the
current sensor input. The resistor R1 and R2 define the current
level into the current sense inputs of the SA2002D. At
maximum rated current the resistor values should be selected
for input currents of 16µARMS.
The value of RSH, if used as the CT's termination resistor,
should be less than the DC resistance of the CT's secondary
winding. The voltage drop across RSH should not be less than
16mVRMS at rated currents.
0
0
1
1
0
0
1
1
Rated
Condition
R2 R1 R0
0
0
1
Rated
Condition
LED Output
(Pulses/
KWh)
220V/10A
6400
Motor Pulse
Rate (Pulses/
KWh)*
100 (200)
Example 2. A manufacturer designing a 220V/80A meter can
choose to have the pins R2, R1 and R0 connected as for a
220V/40A (R2=0, R1=0 and R0=1). In comparison to table 1
the Rated Condition has doubled (17600W), this in turn halves
the LED and Motor Pulse output rates as shown in the
following table:
R2 R1 R0
0
5/10
1
0
Rated
Condition
LED Output
(Pulses/
KWh)
220V/80A
800
Motor Pulse
Rate (Pulses/
KWh)*
50 (100)
sames
SA2002D
OUTPUT SIGNALS
Direction input (DIRI)
The DIRI input pin allows the representation of the measured
energy to be selected. The representation can be of any three
types:
Motor Pulse Output (MOP, MON)
These outputs can be used to drive an electromechanical
counter directly at 100 (200) impulses per kWh. See table 1.
Positive Energy
Pulses are generated on the output if the energy flow is
positive. Any negative energy (reverse energy) flow is
disregarded.
VDD
MOP
VSS
VDD
Negative Energy
Pulses are generated on the output if the energy flow is
negative. Any positive energy flow is disregarded. Negative
energy flow is defined as the condition where the voltage
sense input and current sense input are out of phase (greater
than 90 degrees).
Bi-direct
Pulses are generated on the output if the energy flow is
positive or negative. The energy direction may be ascertained
by monitoring the DIRO pin.
Energy Direction Selection
DIRI
Direction
1
Positive
0
Negative
DIRO
Bi-direct
MON
VSS
DR-01559
tm = 230ms
tm
tm
tm
Figure 5: Motor output MON and MOP
LED Output (LED)
The LED pulse output follows the average power consumption
measured and is intended for calibration purposes. The pulse
rate is dependant on the settings of pins R0, R1 and R2 (see
rated conditions select). The LED output is active low. The LED
waveform is shown below:
VDD
LED
VSS
DR-01332
TLED = 10ms
tLED
Figure 6: LED pulse output
Fast Calibration (FAST)
The SA2002D may be put in a fast calibration mode by setting
FAST to VDD. In this mode the pulse rate is 1252Hz on the LED
output at rated conditions.
An integrated anti-creep function prevents any output pulses if
the measured power is less than 0.02% of the meters rated
current.
Direction Indication (DIRO)
The SA2002D provides information about the energy flow
direction on pin DIRO. A logic 0 on pin DIRO indicates reverse
energy flow. Reverse energy flow is defined as the condition
where the voltage sense input and current sense input are out
of phase (90..270 degrees).
Positive energy flow, when voltage sense and current sense
input are in phase, is indicated on pin DIRO as a logic 1.
The DIRO pin may be used to drive a LED in order to indicate
reverse energy.
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SA2002D
TYPICAL APPLICATION
VOLTAGE DIVIDER
In figure 7, the components required for stand alone power
metering application, are shown. The application uses a shunt
resistor for the mains current sensing. The meter is designed
for 220V/40A IMAX operation.
The voltage divider is calculated for a voltage drop of 14V +
5%(14.7V). Equations for the voltage divider in figure 7 are:
R1+R2+R3=RA and R12 || (R11+P1)=RB. Combining the two
equations gives:
The most important external components for the SA2002D
integrated circuit are the current sense resistors, the voltage
sense resistors as well as the bias setting resistor.
(RA + RB) / 220V = RB / 14.7V
BIAS RESISTOR
R13 defines all on-chip and reference currents. With
R13=24kW, optimum conditions are set. Device calibration is
done on the voltage input of the device.
SHUNT RESISTOR
The voltage drop across the shunt resistor at rated current
should be at least 20mV. A shunt resistor with a value of 625µW
is chosen. The voltage drop across the shunt resistor is 25mV
at rated conditions (Imax). The power dissipation in the current
sensor is:
P=(40A)² x 625µW = 1W.
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 of
the SA2002D at rated conditions.
A 5k trimpot will be used in the voltage channel for meter
calibration. The center position on the pot is used in the
calculations. P1 = 2.5kW and values for resistors R11 = 22kW
and R12 =1MW is chosen.
Substituting the values will result in:
RB = 23.91kW and RA = RB x (230V/14.7V - 1) resulting in RA =
333kW so the resistor values of R1, R2 and R3 are chosen to
be 110kW.
PROGRAMMING
The resistor values are calculated for a 40A rated meter. The
LED pulse rate must be set accordingly by programming pins
R0, R1 and R2. Using the table Rated Conditions Select (On
page 5) pins R0 and R2 is set to VSS and R1 set to VDD. These
settings will configure the SA2002D for 220V/40A operation
with a LED pulse rate of 1600 pulses/kWh. The FAST pin is set
to VSS for normal operation.
According to equation described in the Current Sense inputs
section:
R6 = R7 = ( IL / 16µA ) x RSH / 2
= 40A / 16µA x 625µW / 2
= 781.25W
A resistor with value of 820W is chosen, the 5% deviation from
the calculated value will be compensated for when calculating
resistor values for the voltage path.
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Figure 7: Application Circuit
8/10
LIVE
NEUTRAL
LIVE
NEUTRAL
DR-01569
R14
R10
R13
-2V5
C6
R6
R1
C5
+2V5
R7
D2
R2
D1
SA2002D
NC
CNF
VDD
FAST
R0
R1
R2
VREF
IIP
IIN
U1
NC
MOP
LED
VSS
MON
NC
DIRO
DIRI
IVP
GND
D4
D3
11
12
13
14
15
16
17
18
19
20
-2V5
-2V5
C1
C2
+2V5
R8
R9
220V/40A meter with 1600 pulses/kWh resolution
10
9
8
7
6
5
4
3
2
1
R3
R5
+ C4
+ C3
R4
Direction
LED2
Calibration
LED1
6 5 4 3 2 1 .1 ICNT1
R12
R11
P1
+2V5
SA2002D
sames
sames
SA2002D
Parts List for Application Circuit: Figure 7
Symbol
Description
U1
D1
D2
D3
D4
R1
R2
R3
R4
R5
R6
R7
R8
R9
SA2002D
Diode, Silicon, 1N4002
Diode, Silicon, 1N4002
Diode, Zener, 2.4V
Diode, Zener, 2.4V
Resistor, 110k, 1/4W, 1%, metal
Resistor, 110k, 1/4W, 1%, metal
Resistor, 110k, 1/4W, 1%, metal
Resistor, 680R, 1/4W, 1%, metal
Resistor, 680R, 1/4W, 1%, metal
Resistor, 820R, 1/4W, 1%, metal
Resistor, 820R, 1/4W, 1%, metal
Resistor, 680R, 1/4W
Resistor, 680R, 1/4W
R10
R11
R12
R13
R14
Resistor, 47R, 2W, 5%, wire wound
Resistor, 22k 1/4W, 1%, metal
Resistor, 1M, 1/4W, 1%, metal
P1
C1
C2
C3
C4
Resistor, 24k, 1/4W, 1%, metal
Shunt resistor 625µW
Trim pot, 5k, Multi turn
Capacitor, 220nF
Capacitor, 220nF
Capacitor, 100uF, 16V, electrolytic
C5
Capacitor, 100uF, 16V, electrolytic
Capacitor, 330nF, 250VAC
C6
LED1
LED2
ICNT1
Capacitor, 820nF
3mm Light emitting diode
3mm Light emitting diode
Mechanical counter
Note 1
Note 1
Note 1
Note 2
Note 1: Resistor (R6 and R7) values are dependant upon the selected shunt resistor (R14) value.
Note 2: Capacitor C6 to be positioned as close as possible to supply pins.
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Detail
PDIP20/SOIC20
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PM9607AP
SA2002D
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 (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
PO BOX 15888
LYNN EAST
0039
REPUBLIC OF SOUTH AFRICA
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