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sames

sames

SA2005M

Figure 3: Analog input internal configuration

http://www.sames.co.za

FUNCTIONAL DESCRIPTION

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 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 current are sampled simultaneously by means of a

sigma delta modulator type ADC and power is calculated for

each individual phase.

The power is fed to a programmable adder that allows the

representation of the measured energy to be either total 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 driver outputs represent measured

amounts of energy. Programmable dividers provide flexible

counter as well as calibration LED resolutions.

Outputs for phase fail and voltage sequence faults and energy

direction are available.

Calibration of the device is done on the voltage sense inputs of

the SA2005M.

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.

An integrated anti-creep function ensures that no pulses are

generated at zero line currents.

ELECTROSTATIC DISCHARGE (ESD) PROTECTION

The SA2005M integrated circuit's inputs/outputs are protected

against ESD.

POWER CONSUMPTION

The overall power consumption rating of the SA2005M

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 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.

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)

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.

VOLTAGE

SENSOR

INPUT

IVP

DR-01288

SS

V

CURRENT

SENSOR

INPUTS

IIP

IIN

SS

V

VDD

SS

V

VDD

DD

V

GND