SA2005F Datasheet, PDF (4/10 Pages) Sames – Three Phase Bidirectional Power/Energy Metering IC with Instantaneous Pulse Output

SA2005F
sames
FUNCTIONAL DESCRIPTION
The SAMES SA2005F is a CMOS mixed signal integrated
circuit, which performs three phase power/energy calculations
over a range of 1000:1, to an overall accuracy of better than
Class 1.
The SA2005F is functionally similar to the SA9105F. No
external loop capacitors are required and an precision
oscillator is integrated on chip.
The integrated circuit includes all the required functions for 3-
phase power and energy measurement such as oversampling
A/D converters for the voltage and current sense inputs, power
calculation and energy integration. Internal offsets are
eliminated through the use of cancellation procedures.
The SA2005F generates pulses with a frequency proportional
to the power measured. The pulse rate follows the
instantaneous power measured. The pulse frequency is
proportional to the total sum of the three phases.
POWER CALCULATION
In the application circuit (figure 5), the mains voltages from V1,
V2 and V3, are converted to currents and applied to the voltage
sense inputs IVP1, IVP2 and IVP3.
The current levels on the voltage sense inputs are derived from
the mains voltages (3 x 230VAC) being divided down to 14V
through voltage dividers. The resulting input currents into the
A/D converters are 14µA_RMS through the resistors R8, R9 and
R10.
For the current sense inputs the voltage drop across the
current transformers terminating resistors are converted to
currents of 16µA_RMS at rated conditions, by means of resistors
R1, R2 (Phase 1); R3, R4 (Phase 2) and R5, R6 (Phase 3). The
signals providing the current information are applied to the
current sensor inputs IIN1, IIP1, IIN2, IIP2 and IIN3, IIP3.
The output frequency of the SA2005F energy metering
integrated circuit at rated conditions is 64Hz on FOUT
(PGM0=0, PGM1=1).
One pulse (measured in Watt second) correspond to an energy
measured of 3 x I_RATED x V_RATED / 64Hz.
For a more detailed description see the Input Signals section.
through clamping diodes, in conjunction with the amplifiers
input configuration. The feedback loops from the outputs of the
amplifiers A_I and A_V generate virtual shorts on the signal inputs.
Exact duplications of the input currents are generated for the
analog processing circuitry.
Voltage Reference Connection (VREF)
A bias resistor of 24k provides an optimum bias conditions on
chip. Calibration of the SA2005F should be done on the
voltage inputs of the device as described in Typical
Applications.
Current Sense Inputs (IIN1, IIP1, IIN2, IIP2, IIN3, IIP3)
At rated current the resistor values should be selected for input
currents of 16µA_RMS. Referring to figure 5, the resistors R1 and
R2 on current channel 1, resistors R3 and R4 on current
channel 2 and resistors R5 and R6 on current channel 3, define
the current level into the current sense inputs of the SA2005F.
The current sense inputs saturates at an input current of ±25µA
peak. Resistors R25, R26 and R27 are the current transformer
termination resistors. The voltage drop across the termination
resistors should be at least 20mV at rated conditions. Values
for the current sense inputs are calculated as follows:
R₁ = R₂ = (I_L / 16µA_RMS) x R₂₅ / 2
R₃ = R₄ = (I_L / 16µA_RMS) x R₂₆/ 2
R₅ = R₆ = (I_L / 16µA_RMS) x R₂₇ / 2
Where:
I_L = Line current/CT-ratio
VDD
IIP
CURRENT
VSS
SENSOR
INPUTS
VDD
IIN
VSS
VDD
IVP
VOLTAGE
SENSOR
VSS
INPUT
AI
A_V
INPUT SIGNALS
Analog Input Configuration
The current and voltage sensor inputs are illustrated in figure 3.
These inputs are protected against electrostatic discharge
DR-01288
GND
Figure 3: Analog Input Internal Configuration
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