SA4101A South African Micro-Electronic Systems, SA4101A Datasheet - Page 8

• Manufacturer Part Number: SA4101A
• Description: Single Phase KWH Metering ic With Pulse Output
• Manufacturer: South African Micro-Electronic Systems

These inputs are protected against electrostatic discharge
through clamping diodes.
The feedback loops from the outputs of the amplifiers 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 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.
POWER CONSUMPTION
The power consumption of the SA4101A 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 SA4101A should be done
on the voltage input as described in the Typical Application
section and not on the Vref input.
Current sense input (IIP and IIN)
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 SA4101A. At Maximum Rated
Mains current (I
an input current of 16µA
http://www.sames.co.za
SA4101A
DR-01568
Rsh
N
L
L
N
LOAD
Supply
R3
P1
R4
Supply
MAX
R1
R2
R5
Figure 6: Application circuit
) the resistor values should be selected for
VREF
IIN
IIP
IVP
AGND
RMS
VDD
.
VSS FAST
VDD
SA4101A
SO
REVERSE
DIRO DIRI
R0 R1 R2
MON
MOP
LED
8 8 8 8 8 8 8
VDD
PULSES
I
and A
V
8/16
The values for resistors R1 and R2 can be calculated as
follows:
R1 = R2 = (I
Where I
RSH
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 20mV
Voltage Sense Input (IVP)
The current into the A/D converter should be set at 14µA
Nominal Mains Voltage (V
±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
input. The Nominal Mains Voltage is divided down to 14V
The current into the A/D converter input is set at 14µA
resistor R5 of value 1MW.
Fast Mode Select (FAST)
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.
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.
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.
When the FAST mode is enabled the LED output generates
pulses at a frequency of 1160Hz at I
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.
L
RMS
L
/16µA) x RSH/2
at I
MAX
=
=
.
NOM
Line current
Shunt resistor or termination
). This is to allow a variation of
MAX
and V
sames
sames
NOM
. In this
RMS
RMS
RMS
via
at
.