sames

SA9103C

PDS039-SA9103C-001

REV. D

23-08-1996

FEATURES

Performs bidirectional active and
reactive power/energy, frequency and
voltage measurement

Meets the IEC 521/1036 Specification
requirements for Class 1 AC Watt hour
meters

Protected against ESD

Total power consumption rating below
25mW

Adaptable to different current sensor
technologies

Operates over a wide temperature
range

Serial interface having a RS232 protocol

Precision voltage reference on-chip

Tri-state output to allow parallel
connection of devices

SINGLE PHASE BIDIRECTIONAL POWER/ENERGY

METERING IC WITH SERIAL INTERFACE

4259

Package: DIP-20

SOIC-20

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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

DR-00829

TP9

OSC2

CPON

CPOP

IIN

CPIN

CPIP

VREF

IIP

OSC1

SOUT

SIN

CIP

CIN

COP

CON

GND

IVP

V SS

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BLOCK DIAGRAM

ABSOLUTE MAXIMUM RATINGS*

Parameter

Symbol

Min

Max

Unit

Supply Voltage

-V

-0.3

6.0

Current on any pin

-150

+150

Storage Temperature

STG

-40

+125

°C

Operating Temperature

-10

+70

°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.

VOLTAGE

REF.

OSC

G N D

IIN

ACTIVE

ENERGY

REACTIVE

ENERGY

FREQUENCY

VOLTAGE

ANALOG

SIGNAL

PROCE-

SSING

DR-00830

IVP

VREF

OSC1

IIP

SERIAL

INTERFACE

OSC2

TIMING

SIN

SOUT

V SS

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ELECTRICAL CHARACTERISTICS
(V

= 2.5V, V

= -2.5V, over the temperature range -10°C to +70°C

, unless otherwise

specified.)

Parameter

Symbol

Min

Typ

Max

Unit

Condition

Supply Voltage: Positive

2.25

2.75

Supply Voltage: Negative

-2.75

-2.25

Supply Current: Positive

Supply Current: Negative

Current Sensor Inputs (Differential)

Input Current Range

-25

+25

µA

Peak value

Voltage Sensor Input (Asymetrical)

Input Current Range

-25

+25

µA

Peak value

Pin SOUT

Output Low Voltage

= 5mA

Output High Voltage

-1

= -2mA

Pin SIN

Input High Voltage

-1

Input Low Voltage

Pull-up Current

-I

150

µA

= V

Oscillator

Recommended crystal:
TV colour burst crystal f = 3.5795 MHz

Pin VREF

With R = 24k

Ref. Current

-I

µA

connected to V

Ref. Voltage

1.1

1.3

Referred to V

Extended Operating Temperature Range available on request.

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PIN DESCRIPTION

Pin

Designation

Description

GND

Ground

Positive Supply Voltage

Negative Supply Voltage

IVP

Analog input for Voltage

IIN

Inputs for current sensor

IIP

OSC1

Connections for crystal or ceramic resonator

OSC2

(OSC1 = Input ; OSC2 = Output)

SOUT

Serial Interface Out

SIN

Serial Interface In

CPON

Connections for outer loop capacitors of

CPOP

A/D converter (Voltage)

CPIN

Connections for inner loop capacitors of

CPIP

A/D converter (Voltage)

CIP

Connections for inner loop capacitors of

CIN

A/D converter (Current)

COP

Connections for outer loop capacitors of

CON

A/D converter (Current)

VREF

Connection for current setting resistor

TP9

Test Pin. Must be connected to V

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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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 200µ

). This voltage is

converted to a current of between 0 and 16µA, by means of resistors R

and R

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 (1M

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.

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 A

and A

generate virtual

shorts on the signal inputs. Exact duplications of the input currents are generated
for the analog signal processing circuitry.

VOLTAGE
SENSOR
INPUT

DR-00831

IVP

CURRENT
SENSOR
INPUTS

IIP

IIN

GND

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Electrostatic Discharge (ESD) Protection
The SA9103C integrated circuit's inputs/outputs are protected against ESD .

Power Consumption
The power consumption rating of the SA9103C integrated circuit is less than 25mW.

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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Read, Reset and Read/Reset of integrator for active energy

Read, Reset and Read/Reset of integrator for reactive energy

Read frequency register

RES

RD/
RES

DR-00832

START

BIT

RES

STOP

BIT

RES

RD/
RES

DR-00833

START

BIT

RES

STOP

BIT

DR-00834

START

BIT

STOP

BIT

Read, Reset and Read/Reset of integrator for voltage

By adapting the "Read/Reset" rate to the line current the accuracy of the measurement
can be achieved down to lowest signal levels.

S T A R T

BIT

DR-01152

RD/
RES

R D

RES

R D

RES

STOP

BIT

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From the two bytes of data output by the device, the value for the register can
be derived as shown:

(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).

Register Values

The active and reactive energy measured per count, may be calculated by
applying the following formula:

Energy per Count

V * I

Watt seconds

Where

Rated Voltage

Rated Current

9281 for Active Energy

9281 * 2 for Reactive Energy

The mains frequency may be calculated as follows:

Frequency

Crystal frequency
Register Value * 8

To calculate the measured voltage, the following formula may be used:

Vmeasured =

V * n

14000 * t

Where

rated voltage

time difference between successive reads

difference in register values between
successive reads

The register access codes which can be written to the SA9103C via the serial
communications port are shown in the table below.

REGISTER

READ

RESET

READ-RESET

ACTIVE

$01

$02

$03

RE-ACTIVE

$81

$82

$83

VOLTAGE

$C1

$C2

$C3

FREQUENCY

$41

Data on SOUT

FIRST BYTE

DR-00835

1 0

1 1

1 2

1 3

1 4

1 5

S E C O N D B Y T E

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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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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.

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

c. At pf close to 1, establish error for reactive (Er)

Er = (Reactive (Measured) - Reactive (True)) / Active (Measured)

Reactive (Corrected) = Reactive (Measured) - Er * Active (Measured)

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

Active energy

step 3

Read reactive register

step 4

Calculate Reactive (Measured) as per 2

step 5

Perform error correction
Calculate Reactive (Corrected) as per 3b

Reactive energy

The above five steps must be performed for each measurement cycle.

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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:

and C

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%.

and C

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.

, R

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 200µ

should be avoided.

= R

= (I

/16µA) * RSH/2

Where

= Line current

RSH

= Shunt resistor/termination resistor

, R

and R

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.

defines all on-chip bias and reference currents. With R

= 24k

, 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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Part List for Application Circuit: Figure 1

Item

Symbol

Description

Detail

IC-1

SA9103C

DIP-20/SOIC-20

IC-2

Opto Coupler 4N35

DIP-6

IC-3

Opto Coupler 4N35

DIP-6

Diode, Silicon, 1N4148

ZD1

Diode, Zener, 2.4V, 200mW

ZD2

Diode, Zener, 2.4V, 200mW

XTAL

Crystal, 3.5795MHz

Colour burst TV

Resistor, 1% metal

Note 1

Resistor, 1% metal

Note 1

Resistor, 390k, (230VAC), 1% metal

Resistor, 1M, 1/4W, 1% metal

Resitor, 470

, 2W, 5%, carbon

Resistor, 24k, 1/4W, 1%, metal

Resistor, 680

, 1/4W, 5%

Resistor, 680

, 1/4W, 5%

R10

Resistor, 680

, 1/4W, 5%

R11

Resistor, 100k, 1/4W, 5%

R12

Resistor, 120

, 1/4W, 5%

R13

Resistor, 120k, 1/4W, 5%

R14

Resistor, 3.9k, 1/4W, 5%

R15

Resistor, 120

, 1/4W, 5%

Capacitor, 560pF

Capacitor, 3.3nF

Capacitor, 100nF

C10

Capacitor, 100nF

C11

Capacitor, 0.47µF, 250VAC, polyester

C12

Capacitor, 100nF

C13

Capacitor, 100µF

C14

Capacitor, 100µF

C15

Capacitor, 820nF

RSH

Shunt Resistor

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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Parts List for Application Circuit: Figure 2

Item

Symbol

Description

Detail

IC-1

SA9103C

DIP-20/SOIC-20

XTAL

Crystal, 3.5795MHz

Colour burst TV

RSH

Resistor

Note 1

Resistor, 1%, metal

Note 2

Resistor, 1%, metal

Note 2

Resistor, 390k, (230VAC) 1%, metal

Resistor, 1M, 1/4W, metal

Resistor, 24k, 1/4W, metal

Resistor, 2.2k, 1/4W, 5%

Capacitor, 560pF

Capacitor, 3.3nF

Capacitor, 3.3nF,

Capacitor, 820nF

Note 3

C10

Capacitor, 100nF

C11

Capacitor

Note 4

Current Transformer

Note 1:

See TYPICAL APPLICATIONS when selecting the value of RSH.

Note 2:

Resistor (R1and R2) values are dependant upon the selected value of
RSH.

Note 3:

Capacitor (C9) to be positioned as close to IC-1, as possible.

Note 4:

Capacitor (C11) selected for DC blocking and to minimize phase error
introduced by the current transformer.

Part Number

Package

SA9103CPA

DIP-20

SA9103CSA

SOIC-20

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Any Sales or technical questions may be posted to our e-mail address below:
energy@sames.co.za

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:

012 333-6021

Tel:

Int +27 12 333-6021

Fax:

012 333-8071

Fax:

Int +27 12 333-8071

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.

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