sames
FEATURES
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SA9106 APPLICATION NOTE
PM9106AP
SINGLE PHASE WATT MEASUREMENT MODULE
WITH A 5 DIGIT LED DISPLAY
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Performs power measurement and di-
rectly drives a 5 digit (7 segment) LED
display
Accuracy better than 1% (± 1 count)
Protected against ESD
Total power consumption rating below
800mW
Uses a shunt resistor or for current
sensing
Operates over a wide temperature
range
Precision voltage reference on-chip
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DESCRIPTION
The SAMES single phase Watt measurement module, the PM9106AP includes an on-
board 5 digit (7 segment) Light Emitting Diode (LED) display. Active power is directly
displayed in watts, with a full scale of 20 000 watts.
The measured power is updated approximately every 2 seconds, giving an average
power reading for this period.
This method of calculation takes the power factor into account.
This innovative universal Watt measurement module is ideally suited for the display of
the measured power in single phase, industrial and domestic power measurement
applications.
The application utlises the SAMES SA9106AP single phase Watt measurement
integrated circuit for power measurement and display.
As a safety measure, this application shows the current sensor connected to the neutral
line. In practice, the live line may be used for current sensing, provided that the supply
connections (MAINS) are reversed on the module.
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4358
PDS038-SA9106-001
REV. A
06-09-1995
PM9106AP
BLOCK DIAGRAM
NEUTRAL IN
NEUTRAL OUT
NEUTRAL
(Mains)
LIVE
SHUNT
POWER
SUPPLY
SA9106A
5-DIGIT
WATT
LED
METER
DISPLAY
IC
DR-00913
ABSOLUTE MAXIMUM RATINGS*
Parameter
Symbol
Supply Voltage (Note 1)
V
AC
Current Sense Input (Note 1)
V
IV
Storage Temperature
T
STG
Operating Temperature (Note2)
T
O
Note 1:
Note 2:
Min
-2.5
-25
-10
Max
540
+2.5
+125
+70
Unit
V
V
°C
°C
Voltages are specified with reference to Live.
The SA9106AP integrated circuit is specified to operate over the temperature
range -10°C to +70°C. The module functionality will however depend upon
the external components used.
*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 conditions 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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PM9106AP
ELECTRICAL CHARACTERISTICS
(Over the temperature range -10°C to +70°C, unless otherwise specified.)
Parameter
Supply Voltage
Power Consumption
1
Symbol
V
AC
Min
180
Typ
230
Max
265
800
Unit
V
mW
Condition
Continuous
operation
V
AC
= 230V
Note 1: Power consumption specifications exclude power consumed by the current
sensor.
Note 2: Isolation voltage may be specified, depending on customer requirements.
PIN DESCRIPTION
Designation
MAINS
NEUTRAL IN
NEUTRAL OUT
Description
Voltage supply connection to Neutral line
Voltage supply connection to Live line
Connection to positive side of current sensor
Connection to negative side of current sensor
FUNCTIONAL DESCRIPTION
1. Power Calculation
In the Application Circuit (see Figure 2), the output current from the current sensor
will be between 0 and 16µA (0 to 80A through a shunt resistor of 625µΩ). The current
input stage saturates at input currents greater than18µA
RMS
. The mains voltage
(230V + 15% -20%) is used to supply the circuitry with power and for the power
calculation, together with the current information from the current sensor (shunt
resistor).
The SA9106AP integrated circuit may be adjusted to accomodate any voltage or
current values. The method of calculating external component values is described
in paragraph 5 (Circuit Description).
SAMES offers two evaluation module options, namely 230V/80A and 115/80A.
The calculated power is directly displayed on a 5 digit (7 segment) LED display. The
update interval is approximately every 2 seconds.
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PM9106AP
2.
LED Display
The PM9106AP has an on-board LED display comprising 5 (7 segment) common
cathode digits, as well as a sign LED.
The sign LED is addressed by DIG [5], the most significant digit by DIG [4] and the
least significant digit by DIG [0].
The position of the segments a, b, c, d, e, f and g are given in the diagram below:
a
f
.
e
d
DR-00914
The full scale power displayed is 20 000 watts. An overflow is indicated by a flashing
display.
3.
Electrostatic Discharge (ESD) Protection
The device's inputs/outputs are protected against ESD according to Mil-Std 883C,
method 3015. The modules resistance to transients will be dependant upon the
protection components used.
Power Consumption
The overall power consumption rating for this power metering application (Figure 2),
is under 800mW, excluding the current sensor.
Circuit Description
The Application Circuit (Figure 2) shows the components required for the Watt
measurement module, using a shunt resistor for current sensing.
b
g
c
h
.
4.
5.
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PM9106AP
The most important external components for the SA9106AP device are:
C
1
and C
2
are the outer loop capacitors for the two integrated oversampling A/D
converters. The value of these capacitors is 560pF.
The actual values determine signal to noise and stability performance. The optimum
tolerances should be within ± 10%.
C
3
and C
4
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
2
, R
1
and R
SH
are the resistors defining the current level into the current sense input.
The values should be selected for an input current of 16µA
RMS
into the SA9106AP
at rated line current.
Values for RSH of less than 200µΩ should be avoided.
R
1
= R
2
= (I
L
/16µA
RMS
) * R
SH
/2
Where
I
L
=
R
SH
=
Line current
Shunt resistor/termination resistor
R
3
, R
5
and R
4
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.
R
7
defines all on-chip bias and reference currents. With R
7
= 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 and supplies the A/D converters
and the digital circuitry.
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