SA2005M
ssaammeess
FUNCTIONAL DESCRIPTION
POWER CONSUMPTION
The SAMES SA2005M is a CMOS mixed signal analog/digital
integrated circuit that performs three phase power/energy
calculations across a power range of 1000:1 to an overall
accuracy of better than Class 1.
The overall power consumption rating of the SA2005M
integrated circuit is less than 80mW with a 5V supply.
INPUT SIGNALS
ANALOG INPUT CONFIGURATION
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 current and voltage sensor inputs are illustrated in figure 3.
These inputs are protected against electrostatic discharge
through clamping diodes, in conjunction with the amplifiers
input configuration. The feedback loops from the outputs of the
amplifiers A and A generate virtual shorts on the signal inputs.
I
V
Exact duplications of the input currents are generated for the
analog processing circuitry. The current and voltage sense
inputs are identical. Both inputs are differential current driven
up to ±25µA peak. One of the voltage sense amplifiers input
terminals is internally connected to GND. This configuration is
possible because the voltage sense input is much less
sensitive to externally induced parasitic signals compared to
the current sense inputs.
The integrated circuit includes all the required functions for a
three phase mechanical counter-based meter design. A
precision oscillator, that replaces an external crystal, is
integrated on chip providing a temperature stable time base for
the digital circuitry. A temperature stable voltage reference
integrated on chip generates the reference current used by the
analog circuitry.
Voltage and current are sampled simultaneously by means of a
sigma delta modulator type ADC and power is calculated for
each individual phase.
Voltage Sense Inputs (IVN1, IVN2, IVN3)
The mains voltages are measured by means of resistor
dividers and the divided voltages are converted to currents.
The current into each voltage sense input (virtual ground)
should be set to 14µARMS at rated voltage conditions. The
The power is fed to a programmable adder that allows the
representation of the measured energy to be either total or
absolute sum.
individual mains voltages are divided down to 14V
per
RMS
phase. The resistors R12, R13 and R14 (figure 8) set the
current for the voltage sense inputs. The voltage sense inputs
saturate at an input current of ±25µA peak.
The summed power is integrated and divided down to
represent integrated energy. Pulses on the LED output and on
the mechanical counter driver outputs represent measured
amounts of energy. Programmable dividers provide flexible
counter as well as calibration LED resolutions.
V
DD
Outputs for phase fail and voltage sequence faults and energy
direction are available.
IIP
V
SS
CURRENT
SENSOR
INPUTS
AI
Calibration of the device is done on the voltage sense inputs of
the SA2005M.
V
DD
IIN
The SA2005M may be used in various meter designs by
setting the RE, RA and IM pins to the appropriate state. See
Input Signals section for the configuration settings. These
features enable the meter manufacturer extremely flexible
meter designs from a single integrated circuit.
V
SS
V
DD
IVP
VOLTAGE
SENSOR
INPUT
V
An integrated anti-creep function ensures that no pulses are
generated at zero line currents.
SS
A
V
ELECTROSTATIC DISCHARGE (ESD) PROTECTION
The SA2005M integrated circuit's inputs/outputs are protected
against ESD.
GND
DR-01288
Figure 3: Analog input internal configuration
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http://www.sames.co.za
SAMES [ SAMES ]
