Datasheet SA9903B Datasheet (sames)

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Single Phase Power / Energy IC
with SPI Interface

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

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.

The SA9903B is pin compatible to the SA9603B. New features
include, RMS mains voltage and accurate reactive power
measurements.

Measured values for active and reactive energy, the mains
voltage and frequency are accessible through a SPI bus from
24 bit registers.

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+ 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

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.

TheSA9903B integrated circuit is available in both 20 pin dual­in-line plastic (DIP-20), as well as 20 pin small outline (SOIC-

20) package types.

IIP

IIN

IVP

GND

Dr-01583

CURRENT

ADC

VOLTAGE

ADC

VOLTAGE

REF.

VREF

TEST

ACTIVE

REACTIVE

RMS

VOLTAGE

MAINS.

FREQ.

OSC

OSC2OSC1

Figure 1: Block diagram

VDD

VSS

SPI

DI

DO

SCK

CS

FMO

SPEC-0051 (REV. 2)

1/12

26-02-01

SA9903B

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ELECTRICAL CHARACTERISTICS

(V = 2.5V, V = -2.5V, over the temperature range -10°C to +70°C , unless otherwise specified.)

DD SS

Parameter

Operating temp. Range

Supply Voltage: Positive

Supply Voltage: Negative

Supply Current: Positive

Supply Current: Negative

Symbol

T

O

V

DD

V

SS

I

DD

I

SS

Min

-25

2.25

-2.75 -2.25

#

Typ

Max

+85

2.75

3.56

3.56

5.1

5.1

Current Sensor Inputs (Differential)

Input Current Range

I

II

-25

+25

Voltage Sensor Input (Asymmetrical)

Input Current Range

Oscillator

Pin VREF
Ref. Current
Ref. Voltage

I

IV

Recommended crystal: TV colour burst crystal f = 3.5795 MHz

-I

R

V

R

-25

45

1.1

50

+25

55

1.3

Digital I/O

Unit

°C

V

V

mA

mA

µA

µA

µA

V

Condition

Peak value

Peak value

With R = 24kW
connected to V
Reference to V

SS

SS

Pins SCK
High Voltage
Low Voltage

Pins CS, DI
High Voltage
Low Voltage

Pins FMO, DO
Low Voltage
High Voltage

V

IH

V

IL

f

SCK

t

LO

t

HI

V

IH

V

IL

V

OL

V

OH

V-1

DD

0.6

0.6

V-1

DD

V-1

DD

V+1

SS

800

V+1

SS

V+1

SS

V
V

kHz
µs
µs

V
V

V
V

I = 5mA

OL

I = -2mA

OH

ABSOLUTE MAXIMUM RATINGS*

Parameter Symbol Min Max Unit

Supply Voltage V -V -0.3 6.0 V

Current on any pin I -150 +150 mA

Storage Temperature T -40 +125 °C

Operating Temperature T -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.

DD SS

PIN

STG

O

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3

SA9903B

PIN DESCRIPTION

PIN

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Designation Description

20

8

14

19

1, 2

3

7

10, 11

12

13

GND

V

DD

V

SS

IVP

IIN, IIP

VREF

TEST

OSC1, OSC2

SCK

DO

Analog Ground. The supply voltage to this pin should be mid-way between
V and V .

DD SS

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.

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.

Analog Input for Voltage. The current into the A/D converter should be set at
14µA at nominal mains voltage. The voltage sense input saturates at an

RMS

input current of ±25µA peak.

Inputs for current sensor. The shunt resistor voltage from each channel is
converted to a current of 16µA at rated conditions. The current sense input

RMS

saturates at an input current of ±25µA peak.

This pin provides the connection for the reference current setting resistor.
A 24kW resistor connected to V sets the optimum operating condition.

Manufacturers test pin, connect to V for normal operation.

SS

SS

Connections for a crystal or ceramic resonator. (OSC1 = input; OSC2 = Output)

Serial clock in. This pin is used to stobe data in and out of the SA9903B

Serial data out. Data from the SA9903B is strobed out on this pin. DO is
only driven when CS is active.

15

FMO

Voltage zero crossover. The FMO output generates a pulse (50% duty cycle)
on every rising edge of the mains voltage.

17

18

4, 5, 6, 9, 16

DI

CS

TP4, TP5, TP6,

Serial data in. Data is only accepted during an active chip select (CS).

Chip select. The CS pin is active high.

Manufacturers Test Pins. (Leave unconnected)

TP9, TP16

1

IIN

IIP

2

VREF

3

TP4

4

TP5

5

TP6

6 15

TEST

7

VDD

8

TP9

9

OSC2 OSC1

10

DR-01225

20

GND

IVP

19

18

CS

DI

17

TP16

16

FMO

VSS

14

DO

13

SCK

12

11

Figure 2: Pin connections: Package: DIP-20, SOIC-20

ORDERING INFORMATION

Part Number

SA9903BPA

SA9903BSA

Package

DIP-20

SOIC-20

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SA9903B

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FUNCTIONAL DESCRIPTION

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.

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 SPI interface of the SA9903B has a tri-state output that
allows connection of more than one metering device on a
single SPI bus.

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 A and A
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.

V

DD

IIP

V

CURRENT
SENSOR
INPUTS

SS

V

DD

IIN

V

SS

V

DD

A

I

IV

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
16µA . Values for resistors R6 and R7 may be calculated as

RMS

follows:

R6 = R7 = (I / 16µA ) x RSH / 2
Where I = Max line current

L

L

RSH = Shunt resistor or termination resistor.

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.

Voltage Sense Input (IVP)

The mains voltage is divided to 14V .at nominal mains

RMS

voltage by means of resistors R1, R2, R3 and R4. The current
into the voltage sense input is set at 14µA with resistor R5

RMS

from the voltage divider. The voltage sense input of the AD
converter saturates at an input current of ±25µA peak.

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).

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.

VOLTAGE
SENSOR
INPUT

DR-01288

Figure 3: Analog input internal configuration

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IVP

V

SS

GND

A

V

4/12

SA9903B

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OUTPUT SIGNALS

SERIAL DATA OUT (DO)

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.

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.

POWER CONSUMPTION

The power consumption rating of the SA9903B integrated
circuit is less than 25mW.

SPI - INTERFACE

DESCRIPTION

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.

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:

ID

1

2

3

4

Register

Active

Reactive

Voltage

Frequency

Header

bits

1

1

1

1

1

1

1

1

A5

A4

A3

A2

A1

A0

0

X

X

0

0

0

0

0

X

X

0

0

0

1

0

X

X

0

0

1

0

0

X

X

0

0

1

1

Voltage

FM0

Dr-01498

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Figure 4: Mains voltage zero corssover pin FMO

5/12

+5V (V )

DD

0V (V )

SS

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.

Address locations A5 and A4 are included for compatibility with
future developments.

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.

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 A3A2A1A0

DATA FORMAT

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.

SCK

DI

DO

CS

DR-01545

Parameter

t1

t3

t4

t2

t5

t3

t2

t5

t1

t4

Description

SCK rising edge to DO valid

SCK min high time

SCK min low time

Setup time for DI and CS

before the rising edge of SCK

DI hold time

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Min

625ns

625ns

625ns

20ns

625ns

Max

1.160µs

The content of each register consists of 24 bits of data. The
MSB is shifted out first.

SCK

CS

DI

DO

Read command Register address

1 1 A5 A0A1A2A3A4

0

0 D23 D22 D21 D1 D0 D23 D22 D1 D0

Register Data

Figure 6: SPI Timing diagrams with timing information

Next data register

High impedance

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Figure 5: SPI waveforms

6/12

SA9903B

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ACTIVE AND REACTIVE 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.

Register wrap around

Positive energy flow

Register values

0

................ ................

H7FFFFF

(8388607)

Negative energy flow

DR-01590

Register wrap around

Figure 7: Register increment / decrement showing the

register wrap around

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.

H800000

(8388608)

HFFFFFF

(16777215)

USING THE REGISTER VALUES

ACTIVE ENERGY REGISTER

The active energy measured by the SA9903B is
calculated as follows:

Energy = V x I x N / INT / 320000
V Rated mains voltage of meter

RATED

I Rated mains current of meter

RATED

N Difference in register values between

INT Time difference between successive register
reads (in seconds)

REACTIVE ENERGY REGISTER

The reactive energy measured by the SA9903B is
calculated as follows:

Reactive = V x I x N / INT / 320000
V Rated mains voltage of meter

RATED

I Rated mains current of meter

RATED

N Difference in register values between

INT Time difference between successive register

MAINS VOLTAGE REGISTER

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:

RATED RATED TIME

successive reads (delta value)

TIME

RATED RATED TIME

successive reads (delta value)

TIME

reads (in seconds)

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:

Decimal HexDescription

16767215

16744955

22260

0x00FFD8EF

0x00FF81FB

0x000056F4

Present register value

Previous register value

new_val - old_val =

Valiable

new_val

old_val

delta_val

The register now wraps around so after the next read

the values are as follows:

Present register value

Previous register value

new_val - old_val =

new_val

old_val

delta_val

12260

16767215

-16754955

0x00002FE4

0x00FFD8EF

0x00FFA90B

Computing this delta value will result in incorrect calculations.

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7/12

Voltage = V x V / 700
V Rated mains voltage of meter

RATED

V Voltage register value

REGISTER VALUE

RATED REGISTER VALUE

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:

Frequency = F / 256 / F
F The external crystal frequency.

CRYSTAL

F Bits D9 to D0 of the frequency register.

REGISTER VALUE

Bits D10 to D22 are not used in the frequency register.
Bit D23 is set with the same status as the FMO output.

CRYSTAL REGISTER VALUE

SA9903B

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TYPICAL APPLICATION

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 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.

VOLTAGE DIVIDER

The voltage divider is calculated for a voltage drop of
14V+2.3% (14.33V). Equations for the voltage divider in figure
8 are:

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 = (I / 16µA) x R / 2

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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LSH

= 80A / 16µA x 625µW / 2
=1.5625kW

8/12

SA9903B

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SDO

SDI

CS

R4

GND

FMO

SCK

C2

+2V5

D3

R10

C3

+

D1

C5

R9

C1

-2V5

D4

R11

C4

+

D2

R1 R2 R3

U1

20

GND

IIN

1

R6

R5

19CS18DI17

IVP

VREF3IIP

2

R7

R8

16

TP16

TP44TP35TP26TEST7VDD8TP99OSCO

15

FMO

-2V5

14DO13DI12

VSS

+2V5

11

OSCI

10

C6

dr-01589

X1

SA9903B

-2V5

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RSH

NEUTRAL

LIVE

NEUTRAL

LIVE

Figure 8: Typical application circuit

9/12

SA9903B

Parts List for Application Circuit: Figure 8

samessames

Symbol

U1
R1
R2
R3

R4
R5
R6
R7
R8
R9
R10
R11
RSH
C1

C2
C3

C4
C5
C6
D1
D2

D3
D4
X1

Description

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

Capacitor, 220nF, ceramic

Capacitor, 220uF, 16V, electrolytic

Capacitor, 220uF, 16V, electrolytic

Capacitor, 470nF, 250VAC, polyester
Capacitor, 820nF, ceramic
Diode, 1N4003

Diode, 1N4003

Diode, Zener, 2.5V

Diode, Zener, 2.5V

Crystal, 3.579545MHz

Detail

DIP-20/SOIC-20

Note 1

Note 1: Capacitor C6 to be positioned as close as possible to supply pins V and V of U1 as possible.

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10/12

DD SS

SA9903B

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11/12

PM9607AP

SA9903B

samessames

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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:

For the latest updates on datasheets, please visit our web site:

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DIVISION OF LABAT TECHNOLOGIES (PTY) LTD

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