SA2102D
sames
These inputs are protected against electrostatic discharge
through clamping diodes.
The values for resistors R1 and R2 can be calculated as
follows:
The feedback loops from the outputs of the amplifiers AI and AV
generate virtual shorts on the signal inputs. Exact duplications
of the input currents are generated for the analog signal
processing circuitry.
R1 = R2 = (IL/16µA) x RSH/2
Where IL
RSH
=
=
Line current
Shunt resistor or termination
resistor if a CT is used as the current sensor.
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
AGND. This is possible because the voltage sense input is
much less sensitive to externally induced parasitic signals
compared to the current sense inputs.
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 20mVRMS at IM
XA
Voltage Sense Input (IVP)
The current into the A/D converter should be set at 14µARMS at
Nominal Mains Voltage (VNOM). This is to allow a variation of
10% for the mains voltage without saturating the voltage
sense input. The voltage sense input saturates at an input
current of 25µA peak. Referring to Figure 6 the typical
connections for the voltage sense input is illustrated.
Resistors R3, R4 and R5 set the current for the voltage sense
POWER CONSUMPTION
The power consumption of the SA2102D integrated circuit is
less than 25mW.
INPUT SIGNALS
Voltage Reference (VREF)
A bias resistor of 47kW sets optimum bias and reference
conditions on chip. Calibration of the SA2102D should be done
on the voltage input as described in the Typical Application
section and not on the Vref input.
input. The Nominal Mains Voltage is divided down to 14VRMS
.
The current into the A/D converter input is set at 14µARMS via
resistor R5 of value 1MW.
Fast Mode Select (FAST)
Current sense input (IIP and IIN)
The FAST pin is used to select between STANDARD and
FAST mode. Leaving this pin open or connecting to Vss
enables the STANDARD mode and connecting to Vdd
enables FAST mode.
Figure 6 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 SA2102D. At Maximum Rated
Mains current (IMAX) the resistor values should be selected for
an input current of 16µARMS
.
When STANDARD mode is enabled the LED output pulses at
a low frequency. This low frequency allows a longer
accumulation period and the output pulses are therefore
proportional to the average power consumption measured.
VDD
N
Supply
L
VDD
Supply
REVERSE
The Rated Select Condition pins (R0,R1 andR2) are used to
select different LED output frequencies which in turn selects
the applications meter constant. Refer to figure 8 for the LED
output timing diagram in STANDARD mode.
PULSES
VDD
DIRO DIRI
LED
R1
IIN
Rsh
IIP
R2
R5
When the FAST mode is enabled the LED output generates
R3
pulses at a frequency of 1160Hz at IMAX and VNOM
. In this
IVP
SA2102D
8 8 8 8 8 8 8
mode the pulse frequency is proportional to the
instantaneous power consumption measured. This mode is
used for meter calibration purposes and can also be used
when interfacing to a microcontroller. Refer to figure 9 for the
LED output timing diagram in FAST mode.
R4
AGND
P1
MOP
MON
R2
VREF VSS FAST SO R0 R1
L
LOAD
N
DR-01568
Figure 6: Application circuit
8/16
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