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sames

sames

SA2002E

http://www.sames.co.za

FUNCTIONAL DESCRIPTION

The SA2002E 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 1-

phase power and energy measurement such as two

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 SA2002E generates pulses, the frequency of

which is proportional to the measured power consumption.

One frequency output (FOUT) is available. The pulse rate

follows the instantaneous power consumption measured.

POWER CALCULATION

In the application circuit (figure 6), the voltage drop across the

shunt will be between 0 and 16mV

(0 to 80A through a shunt

RMS

resistor of 200µW) The voltage is converted to a current of

between 0 and 16uA

, by means of resistors R1 and R2. The

RMS

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

peak.

For the voltage sensor input, the mains voltage (230VAC) is

divided down through a divider (R3, R4 and P1) to 14V

. The

RMS

current into the A/D converter input is set at 14µA

at nominal

RMS

mains voltage, via resistor R5 (1MW). P1 may be varied for

calibration purposes.

In this configuration, with a mains voltage of 230V and a

current of 80A, the output frequency measured on the FOUT

pin is 1360Hz. In this case one pulse on FOUT correspond to

an energy consumption of 18.4kW/1360Hz = 13.53Ws.

ANALOG INPUT CONFIGURATION

The input circuitry of the current and voltage sensor inputs is

illustrated in figure 7. These inputs are protected against

electrostatic discharge through clamping diodes. The

feedback loops from the outputs of the amplifiers A and A

IV

generate virtual shorts on the signal inputs. Exact duplications

of the input currents are generated for the analog signal

processing circuitry.

Figure 6: Application circuit

Figure 7: Internal analog input configuration

GND

VDD

DR-01148

VOLTA GE

SENSOR

INPUT

IVP

SS

V

IIN

IIP

CURRENT

SENSOR

INPUTS

SS

V

SS

V

VDD

DD

V

DR-01584

R3

VDD

VREF

IIP

IIN

GND

IVP

VSS

FOUT

U1

SA2002E

R4

R5

R1

R2

R6

L

N

L

N

RSH

P1

GND

GND

VSS

VDD

GND

Supply

VDD

VSS

Pulse output