SA2005P
FUNCTIONAL DESCRIPTION
The SAMES SA2005P 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 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 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 currents are sampled simultaneously by means of
a sigma delta modulator type ADC and power is calculated for
each individual phase. A programmable channel balance on
each channel is used for individual channel calibration.
The scaled power is fed to a programmable adder that allows
the representation of the measured energy to be either total
sum or absolute sum.
The summed power is integrated and divided down to
represent integrated energy. Pulses on the LED output and on
the mechanical counter outputs represent measured amounts
of energy. The programmable dividers provide flexible counter
and calibration LED resolutions.
Outputs for phase voltage fail and voltage sequence faults and
energy direction are available.
The SA2005P does not require any external trim-pots or
resistor ladders as meter calibration and configuration data is
stored on a small external EEPROM. The SA2005P configures
itself from the EEPROM during power up. These features
enables meter manufacturers flexible meter designs from a
single integrated circuit.
sames
operation of the meter. Every data byte stored in the EEPROM
is protected with a checksum byte to ensure data integrity.
ELECTROSTATIC DISCHARGE (ESD) PROTECTION
The SA2005P integrated circuit's inputs/outputs are protected
against ESD.
POWER CONSUMPTION
The overall power consumption rating of the SA2005P
integrated circuit is less than 80mW with a 5V supply.
INPUT SIGNALS
ANALOG INPUT CONFIGURATION
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
I
and A
V
generate virtual shorts on the signal inputs.
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.
Current Sense Inputs (IIN1, IIP1, IIN2, IIP2, IIN3, IIP3)
The current sense inputs connects to a termination resistor
connected across the terminals of a current transformer. At
V DD
IIP
CURRENT
SENSOR
INPUTS
VSS
VDD
A
I
IIN
VSS
VDD
IVP
AUTOMATIC DEVICE CONFIGURATION (BOOT UP)
During power up, registers containing configuration and
calibration information is updated from an external EEPROM.
The device itself never writes tot he EEPROM so any write
protect features offered by manufacturer of EEPROM’s may
be used to protect the configuration and calibration constant of
the meter. The device reloads its configuration every 1193
seconds from the external EEPROM in order to ensure correct
VOLTAGE
SENSOR
INPUT
V SS
A
V
GND
DR-01288
Figure 3: Analog input internal configuration
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SAMES [ SAMES ]
