SA2002D Datasheet, PDF (5/10 Pages) Sames – Single Phase Kilowatt-hour Metering IC for Mechanical Display Applications

SA2002D
sames
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.
ELECTROSTATIC DISCHARGE (ESD)
PROTECTION
The SA2002D integrated circuit's inputs/outputs are protected
against ESD.
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.
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 16µA_RMS.
The values for resistors R1 and R2 can be calculated as
follows:
R1 = R2 = (I_L/16µA) x RSH/2
Where I_L
=
Line current
RSH
=
Shunt resistor or termination
Resistor if a CT is used as the current sensor.
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
16mV_RMS at rated currents.
Voltage Sense Input (IVP)
The current into the A/D converter should be set at 14µA_RMS 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 14V_RMS. The current
into the A/D converter input is set at 14µA_RMS via resistor R5.
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
000
001
010
011
100
101
110
111
Rated
Condition
LED Output
(Pulses/
KWh)
220V/10A
220V/20A
220V/40A
220V/80A
220V/6A
220V/30A
220V/60A
Test Mode
6400
3200
1600
800
6400
3200
1600
Test Mode
Table 1
Motor Pulse
Rate (Pulses/
KWh)*
100 (200)
100 (200)
100 (200)
100 (200)
100 (200)
100 (200)
100 (200)
-
*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 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:
R2 R1 R0
001
Rated
Condition
220V/10A
LED Output
(Pulses/
KWh)
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
010
Rated
Condition
220V/80A
LED Output
(Pulses/
KWh)
800
Motor Pulse
Rate (Pulses/
KWh)*
50 (100)
http://www.sames.co.za
5/10