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sames

SA2002P

Figure 3: Analog input internal configuration

http://www.sames.co.za

FUNCTIONAL DESCRIPTION

The SA2002P is a CMOS mixed signal Analog/Digital

integrated circuit, which performs 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

single 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.

In Figure 9, the voltage drop across the shunt r

The input circuitry of the current and voltage sensor inputs are

illustrated in figure 3. These inputs are protected against

electrostatic discharge through clamping diodes.

Various pulse outputs (MOP, MON and LED) are available.

The pulse rate on these pins follows the active power

consumption measured.

A 5V stepper motor may be driven directly from the SA2002P

by connecting it between the MOP and MON pins, alternatively

an impulse counter may be driven directly by connecting it

between MOP and V .

The SA2002P configures itself from an external low cost

EEPROM that contains all meter configuration and calibration

data. No external trimming is required. Calibration of the

device may be fully automated.

esistor should

be more than 16mV at rated load current. The voltage is

converted to current by means of resistors R

and R . The

current sense input saturates at an input current of ±25µA

peak.

The mains voltage (230VAC) is divided down through a divider

to

. The current into the A/D converter input is set at

at nominal mains voltage, via resistor R (1M

.

See Device Configuration for more details on the processing of

measured energy to frequency outputs.

The feedback loops from the outputs of the amplifiers A and A

generate virtual shorts on the signal inputs. Exact duplications

of the input currents are generated for the analog signal

processing circuitry.

SS

POWER CALCULATION

ANALOG INPUT CONFIGURATION

10

11

7

IV

14V

14µA

RMS

RMS

W)

AUTOMATIC DEVICE CONFIGURATION (BOOT UP)

ELECTROSTATIC DISCHARGE (ESD)

PROTECTION

POWER CONSUMPTION

During power up, registers containing configuration and

calibration information are updated from an external

EEPROM. The device itself never writes to the EEPROM so

any write protect features offered by manufacturer of

EEPROM's may be used to protect the configuration and

calibration constants of the meter. The device reloads its

configuration every 1193 seconds from the external EEPROM

in order to ensure correct operation of the meter. Every data

byte stored in the EEPROM is protected with a checksum byte

to ensure data integrity.

The SA2002P integrated circuit's input's/outputs are protected

against ESD.

The power consumption rating of the SA2002P integrated

circuit is less than 30mW.

VOLTAGE

SENSOR

INPUT

IVP

DR-01288

SS

V

CURRENT

SENSOR

INPUTS

IIP

IIN

SS

V

VDD

SS

V

VDD

DD

V

GND