Datasheet SA9604APA, SA9604ASA Datasheet (SAMES)

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THREE PHASE BIDIRECTIONAL POWER/ENERGY

METERING IC WITH SERIAL SPI INTERFACE

FEATURES

■ Performs bidirectional active and

reactive power/energy measurement

■ Voltage and frequency measurement

■ Individual phase information

accessable

■ SPI communication bus

■ Meets the IEC 521/1036 Specification

requirements for Class 1 AC Watt hour
meters

The SAMES SA9604A Bidirectional Three
Phase Power/Energy metering integrated
circuit has a serial interface, ideal for use
with a µ-Controller. The SA9604A performs
the calculation for active and reactive power
or energy, mains voltage sense and
frequency.

The measurements performed and the
resultant register values are provided for
individual phases.

The integrated values for active and reactive
energy, as well as the mains voltage sense
and frequency information, are accessable
through the SPI as 24 bit values.

This innovative universal three phase power/
energy metering integrated circuit is ideally
suited for energy calculations in applications
such as primary industrial metering and
factory energy metering and control.

The SA9604A 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.

SA9604A

■ Protected against ESD

■ Uses current transformers for current

sensing

■ Excellent long term stability

■ Operates over a wide temperature

range

■ Precision Voltage Reference on-chip

PIN CONNECTIONSDESCRIPTION

IP2
IN2

VP3
IP3

IN3

V

DD

150

0

SC1

1
2
3
4
5
6
7
8
9

10

DR-01306

Package: DIP-20

20
19
18
17
16
15
14
13
12
11

SOIC-20

IVP2
IIN1

IIP 1
IVP1
GND

VREF
V

SS
CS
DI

OSC2

SA9604A

PDS039-SA9604A-001 REV. 5 29-05-00

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SA9604A

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BLOCK DIAGRAM

V

V

DD

SS

IP1
IN1

IP2
IN2
IP3
IN3

ANALOG

SIG NAL

ACTIVE

ENERGY

REACTIVE

ENERGY

VOLTAGE

SPI

DI
DO
SCK
CS

FREQUENCY

PROCES-

VP1
VP2
VP3

GND

DR-01307

SING

VOLTAGE

REF.

F150

OS C

OSC2VREF OSC1

ABSOLUTE MAXIMUM RATINGS*

Parameter Symbol Min Max Unit

Supply Voltage VDD -V
Current on any pin I
Storage Temperature T
Operating Temperature T

PIN

STG

O

SS

-0.3 6.0 V

-150 +150 mA

-40 +125 °C

-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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SA9604A

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

Operating temp. range T
Supply Voltage: Positive V
Supply Voltage: Negative V
Supply Current: Positive I
Supply Current: Negative I

DD

SS
DD
SS

-25 +85 °C

O

2.25 2.75 V

-2.75 -2.25 V
810mA
810mA

Current Sensor Inputs (Differential)
Input Current Range I

II

-25 +25 µ A Peak value
Voltage Sensor Input (Asymetrical)
Input Current Range I

IV

-25 +25 µ A Peak value
Pin DO

Low Voltage V
High Voltage V

OL

VDD-1 V IOH = -2mA

OH

VSS+1 V IOL = 5mA

Pin DI

High Voltage V
Low Voltage V

VDD-1 V

IH
IL

VSS+1 V VIN = V

SS

Pin SCK

High Voltage V
Low Voltage V

f

VDD-1 V

IH
IL

SCK

t

LO

t

HI

0.6 µs

0.6 µs

VSS+1 V VIN = V

800 kHz

SS

Pin CS

High Voltage V
Low Voltage V

VDD-1 V

IH
IL

VSS+1 V VIN = V

SS

Pin F150

Low Voltage V
High Voltage V

OL

VDD-1 V IOH = -2mA

OH

VSS+1 V IOL = 5mA

Oscillator Recommended crystal:

TV colour burst crystal f = 3.5795 MHz

Pin VREF With R = 47kΩ

Ref. Current -I
Ref. Voltage V

#

Extended Operating Temperature Range available on request.

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22.5 25 27.5 µA connected to V

R

1.1 1.3 V Reference to V

R

SS
SS

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SA9604A
PIN DESCRIPTION

Pin Designation Description

16 GND Ground
6 V

14 V

DD

SS

Positive Supply Voltage

Negative Supply Voltage
17 IVP1 Analog input for Voltage: Phase 1
20 IVP2 Analog input for Voltage: Phase 2

3 IVP3 Analog input for Voltage: Phase 3
19 IIN1 Inputs for Current sensor:Phase 1
18 IIP1

2 IIN2 Input for Current sensor: Phase 2

1 IIP2

5 IIN3 Input for Current sensor: Phase 3

4 IIP3

10 OSC1 Connections for crystal or ceramic resonator
11 OSC2 (OSC1 = Input; OSC2 = Output)

9 DO Serial Interface Out

12 DI Serial Interface In

8 SCK Serial Clock In

13 CS Chip Select (Active High)

7 FM150 Voltage Sense Zero Crossover

15 VREF Connection for current setting resistor

FUNCTIONAL DESCRIPTION

The SA9604A is a CMOS mixed signal Analog/Digital Integrated Circuit, which performs
the measurement of active power, reactive power, voltage and frequency.

Internal offsets are eliminated through the use of cancellation procedures. The SA9604A
integrates the measured active and reactive power consumption and the average mains
voltage into 24 bit integrators, which are accessable via the SPI bus. The mains
frequency information is also available as a 24 bit register value.

The zero crossover of each voltage sense input is signalled on the FM150 (pin 7) output.
This output of 150Hz will allow monitoring by a microcontroller to synchronise with internal
timing for data aquisition. Refer to 5.5 for further information.

The SA9604A has tristate output to allow connection of more than one metering device
on a single SPI bus.

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1. Power calulation

D

In the Application Circuit (Figure 1), the voltages from Line 1, Line 2 and Line 3, are
converted to currents and applied to the voltage sense inputs IVN1, IVN2 and IVN3.

The current levels on the voltage sense inputs are derived from the mains voltage
(3 x 230 VAC) being divided down through voltage dividers to 14V
input currents into the A/D converters are 14µA

through the resistors R15, R16 and

RMS

. The resulting

RMS

R17.
For the current sense inputs, the voltages across the current transformers terminating

resistors are converted to currents of 16µA

for rated conditions, by means of

RMS

resistors R8, R9 (Phase 1); R10, R11 (Phase 2); and R12, R13 (Phase 3).
The signals providing the current information are applied to the current sensor

inputs: IIN1; IIP1; IIN2; IIP2; IIN3; and IIP3.

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 copies of the input currents are generated for the
following analog signal processing circuitry.

V

DD

SA9604A

IIP

V

CURRENT
SENS OR
INPUTS

IIN

IV P

VOLTAGE
SENS OR
INPUT

R-01308

SS

V

DD

V

SS

V

DD

V

SS

GND

3. Electrostatic Discharge (ESD), Protection

The SA9604A Integrated Circuits inputs/outputs are protected against ESD.

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4. Power Consumption

The power consumption rating of the SA9604A integrated circuit is less than 50mW.

5. SPI - INTERFACE

5.1 Description

The serial peripheral interface (SPI) is a synchronous bus for data transfer and is
used when interfacing the SA9604A with any micro-controller. Four pins are used
for the SPI. The four pins are DO (Serial Data Out), DI (Serial Data In), CE (Chip
Enable), and SCK (Serial Clock). The SA9604A is the slave device in an SPI
application, with the micro-controller being the master. The DI and DO pins are the
serial data input and output pins for the SA9604A, respectively. The CE input is used
to initiate and terminate a data transfer. The SCK pin is used to synchronize data
movement between the master (micro-controller) and the slave (SA9604A) devices.

The serial clock (SCK), which is generated by the micro-controller, is active only
during address and data transfer to any device on the SPI bus.

5.2 Register Access

There are four registers for each phase which can be read: active, reactive, voltage
and frequency. Any of these registers may be chosen as the initial register to read.
If the SCK clock input continues after the first register has been read, the contents
of subsequent registers will be output on the DO pin. Transfer will continue until CS
is brough inactive.

To enable registers for reading, the sequence 1 1 0 (6

) must precede the 6 bit

HEX

address of the register being accessed.
The various register addresses are shown in the table below:

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ID REGISTER A5 A4 A3 A2 A1 A0

1 Active: Phase 1 X X 0 0 0 0
2 Reactive: Phase 1 X X 0 0 0 1
3 Voltage: Phase 1 X X 0 0 1 0

4 Frequency: Phase 1 X X 0 0 1 1
5 Active: Phase 2 X X 0 1 0 0
6 Reactive: Phase 2 X X 0 1 0 1
7 Voltage: Phase 2 X X 0 1 1 0
8 Frequency: Phase 2 X X 0 1 1 1

9 Active: Phase 3 X X 1 0 0 0
10 Reactive: Phase 3 X X 1 0 0 1
11 Voltage: Phase 3 X X 1 0 1 0
12 Frequency: Phase 3 X X 1 0 1 1

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Address locations A4 and A5 have been included to ensure compatibility with future
SAMES integrated circuit developments.

When CS is high, data input on pin DI is clocked into the device on the rising edge
of SCK. The data clocked into DI will comprise of 1 1 0 A5 A4 A3 A2 A1 A0, in this
order.

5.3 Data Output

After the least significant digit of the address has been entered on the rising edge
of SCK, the output DO goes low with falling edge of SCK. Each subsequent falling
edge transaction on the SCK pin will validate data of the register contents on pin DO.

The contents of each register consists of 24 bits of data output on pin D0, starting
with the most significant digit, D23.

5.4 Frequency Register

For the frequency register only bits D15 ... D0 are used for calculations. The upper
seven bits (D23 ... D17) must still be clocked out, as important frequency information
can be derived from these data bits.

Bit D17 changes with every rising edge of the mains voltage (25Hz square wave for
50Hz mains system). Bit D18 displays a frequency of D17/2 and D19 displays a
frequency of D17/4.

The phase error status may be ascertained from bits D20 and D21. The table below
may be used for this purpose:

SA9604A

Frequency data Bits

D21

0
1
1

D20

0
0
1

No phase error
Phase sequence error (2 phase swapped)
Missing phase

Description

The phase error status is merged on all three frequency registers.
Bits D16, D22 and D23 are not used.

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SA9604A

5.5 SPI Waveforms

The read cycle waveforms are shown below:

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SPI TIMING

SA9604A

Parameter

t1
t2

t3
t4

Description

SCK rising edge for data valid
Setup time for DI and CS before the rising edge

of SCK
SCK min high time
SCK min low time

Min

0,560
0,625
0,625

Max

1,160

Unit

µS

µS
µS
µS

5.6 Synchronised Reading of Registers

The SA9604A integrated circuit updates the registers on a continual basis. The
SA9604A register content in latched onto the SPI interface as soon as a read
command has been detected or the next register is addressed during continual
access. The registers can be accessed at any time however for maximum stability
the time between readings must be in multiples of 8 mains cycles. The internal offset
cancellation procedure requires 8 mains cycles to complete. The 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. This methodology holds
true for Active, Reactive and Voltage registers. The data read from the registers

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SA9604A

represents the active power, reactive power and voltage integrated over time. The
increase of decrease between readings is the energy consumption. The registers
are not affected during access. No error is possible during read, because all control
signals are generated on chip. The registers can be accessed in any sequence at
any time without problems.
The voltage sense zero crossing is a 1mS pulse available on FM150, (Pin 7). This
information allows a supervisor (ie: microcontroller) to monitor when the next read
operation should be performed. The FM150 output is only suitable if all phase
voltages are connected. Should one or more phases fail the FM150 output becomes
unstable. A better approach would be to monitor the upper bits of the frequency
register (18, 19). A measurement cycle is completed when these bits change to the
same state again (00..00 or 01..01 or 10..10 or 11..11).

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Phase 1

F

Any sequence of 24 pulse’s is equal to 1 measurement cycle

1mS

+5V

0V (Vss)

Phase 2

Phase 3

FM150 OUTPUT

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SA9604A

SA9604A

6. Register Values

The 24 bit registers are up/down counters, which increment or decrement at a rate
of 640k/s (640k*2/PI for reactive) at rated conditions. The energy register values will
increment for positive energy flow and decrement for negative energy flow as can
be seen in the following diagram:

register wrap around
positive energy flow

Register values

0

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

H7FFFFF
(8388607)

H800000

(8388608)

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

HFFFFFF

(16777215)

negative energy flow

register wrap around

At power-up the register values are underfined and for this reason the msb of the
delta value (delta value = present register value - previous register value) should
be regarded as an indication of the measured energy direction. (0 = positive, 1 =
negative).

The delta value for the energy registers is between 0 and 8388607 for positive
energy flow and between 0 and -8388607 for negative energy flow. For voltage the
maximum usable delta value is 16777215 as voltage is in a positive direction only.

When reading the registers care should be taken to check for a wrap around
condition.

As an example lets assume that with a constant load connected the delta 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

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SA9604A

period between reads). However this will not be true when a wrap around occurs as
the following example will demonstrate:

Previous register value = 16744955
Present register value = 16767215
Delta value = 16767215 - 16744955 = 22260
After the next read the values are as follows:
Previous register value = 16767215
Present register value = 12260
Delta value = 12260 - 16767215 = -16754955

Computing this delta value will result in incorrect readings, in other words a wrap
around has occurred. A typical function to check for wrap around condition would
be as follows:

Function Check (delta_value);
Begin

Temp_delta_value = abs(delta_value); {get rid of the minus sign for example:

abs(-151) = 151}
if Temp_delta_value)> 8388607 then
begin
if (delta_value)>0 then result : = (16777216-delta_value) *-1
else result : = (16777216+delta_value);
end;
end; {end function}

At rated conditions, the time for wrap around is as follows:

18.6 seconds for voltage
13 seconds for active and 21 seconds for reactive
The active and reactive energy measured per count, may be calculated by applying

the following formula:

VI

Energy per Count =

Watt seconds

K

Where V = Rated Voltage

I = Current (I

max

)

K = 640 000 for Active Energy

2

π

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640 000 *

for Reactive Energy

SA9604A

Example:

V = 230V
I = 80A
Active Power = 230V x 80A x (n/t)/640000
Reactive Power = 230V x 80A (n/t)/(640000 x 2)/Pi)
n = Difference in register values between successive reads (delta

value)

t = Time difference between successive reads (in seconds)
To calculate the measured voltage, the following formula is applied:

V

measured

=

V * n
940 000 * t

Where V = Rated Voltage

t = Time difference between successive reads
n = Difference in register values between

successive reads

The Voltage calculated is the average voltage. The voltage measurement will give
an accuracy of better than 1% for a voltage range of 50% to 115% of the rated mains
voltage if the voltage is a pure sine wave.

The mains frequency may be calculated as follows:

Crystal frequency

Frequency =

Register Value * 2

7. Calibration

For accurate results we would recommend the following software calibration
procedure:

7.1 Active energy

Establish a calibration factor for active energy (Ka) at pf close to 1.

Active Measured = Active_Register_Value x Ka

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7.2 Reactive Energy

With a pf close to 0 establish the phase error:
PhaseError = arctan (VARMeaured / ActiveMeasured)
For each measurement calculate the following:

SA9604A

VA = ActiveMeasured2 + VARmeasured

2

PHIcalibrated = arctan (VARmeasured / ActiveMeasured)
PHICorrected = PHIcalibrated - PhaseError

VARtrue = VA * sin(PHICorrected)

TYPICAL APPLICATION

In the Application Circuit (Figure 1), the components required for a three phase energy
metering application are shown.

Terminated current sensors (current transformers) are connected to the current sensor
inputs of the SA9604A through current setting resistors (R8 ..R13).

The resistor values for standard operation are selected for an input current of 16µA

RMS

into the SA9604A, at the rated line current.
The values of these resistors are calculated as follows:
Phase 1:
R8 = R9 = (IL1/16µA

) * R18/2

RMS

Phase 2:
R10 = R11 = (IL2/16µA

) * R19/2

RMS

Phase 3:
R12 = R13 = (IL3/16µA
Where I
R18, R19 and R

LX

20

) * R20/2

RMS

= Secondary CT current at rated conditions.
= Current transformer termination resistors for the three phases.

R1 + R1A, R4 and R15 set the current for the phase 1 voltage sense input. R2 + R2A, R5 +
P5 and R16 set the current for phase 2 and R3 + R3A, R6 and R17 set the current for phase

3. The values should be selected so that the input currents into the voltage sense inputs
(virtual ground) are set to 14µA

for the rated line voltage condition. Capacitors C1, C2

RMS

and C3 are for decoupling and phase compensation.
R

defines all on-chip bias and reference currents. With R14 = 47kΩ, optimum conditions

14

are set. R

may be varied by up to ± 10% for calibration purposes. Any changes to R

14

will affect the output quadratically (i.e: ∆R = +5%, ∆P = +10%).
XTAL is a colour burst TV crystal (f = 3.5795 MHz) for the oscillator. The oscillator

frequency is divided down to 1.78975 MHz on-chip, to supply the digital circuitry and the
A/D converters.

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L

L

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AINS VOLTAGES

INE 1
INE 2

INE 3

R1
R2

R3

VI2P
VI2N

GND

VI3P
VI3N

GND

F150
SCK
D0

R19

R20

R1A
R2A

R3A

GND

C3

R6

VDD

R11
R10

R17
R13

R12

1

2
3
4

5

6

7

8

9

10

DR-01310

S A9604A

IC-1

XTAL

SA9604A

Figure 1: Application Circuit for Three Phase Power/Energy Measurement

R16

20
19
18
17
16
15

14
13

CS

12

DI

11

R8
R9

R15

VSS

C2

C1

R14

GND

R18

VI1P

VI1N

GND

R5R4

VDD

C13

R7

C12

R21

GND

C14

VSS

Parts List for Application Circuit: Figure 1

Item Symbol Description Detail

1 IC-1 Integrated circuit, SA9604A DIP-20, SOIC-20
2 XTAL Crystal, 3.5795 MHz Colour burst TV
3 R1 Resistor, 200k, 1%, ¼W
4 R1A Resistor, 180k, 1%, ¼W
5 R2 Resistor, 200k, 1%, ¼W
6 R2A Resistor, 200k, 1%, ¼W
7 R3 Resistor, 200k, 1% , ¼W
8 R3A Resistor, 180k, 1%, ¼W

9 R4 Resistor, 24k, 1%, ¼W
10 R5 Resistor, 24k, 1%, ¼W
11 R6 Resistor, 24k, 1%, ¼W
12 R7 Resistor, 820Ω, 1%, ¼W

13 R8 Resistor Note 1
14 R9 Resistor Note 1
15 R10 Resistor Note 1
16 R11 Resistor Note 1
17 R12 Resistor Note 1
18 R13 Resistor Note 1
19 R14 Resistor, 47k, 1%, ¼W
20 R15 Resistor, 1M, 1%, ¼W
21 R16 Resistor, 1M, 1%, ¼W
22 R17 Resistor, 1M, 1%, ¼W
23 R18 Resistor Note 1
24 R19 Resistor Note 1
25 R20 Resistor Note 1
26 R21 Resistor, 820Ω, 1%, ¼W
27 C1 Capacitor, electrolytic, 1µF, 6V Note 2
28 C2 Capacitor, electrolytic, 1µF, 6V Note 2
29 C3 Capacitor, electrolytic, 1µF, 6V Note 2
30 C12 Capacitor, 820nF Note 3
31 C13 Capacitor, 100nF
32 C14 Capacitor, 100nF

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SA9604A

Note 1: Resistor (R8, R9, R10, R11, R12 and R13) values are dependant upon the

selected value of the current transformer termination resistors R18, R

19

and R20.

Note 2: Capacitor values may be selected to compensate for phase errors caused

by the current transformers.

Note 3: Capacitor (C12) to be positioned as close to Supply Pins (VDD & VSS) of

IC-1, as possible

ORDERING INFORMATION

Part Number Package

SA9604APA DIP-20
SA9604ASA SOIC-20

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Notes:

SA9604A

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SA9604A

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 adress below:
[e-mail]

For the latest updates on datasheets, please visit our 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: [phone] Tel: Int [phone]
Fax: [phone] Fax: Int [phone]

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