SPEC-1081 (REV. 2)

7/15

29-09-2017

SA4101A

FUNCTIONAL DESCRIPTION

Theory of Operation

The SA4101A is a CMOS integrated circuit, which performs

power/energy calculations across a dynamic range of 500:1

to an accuracy that exceeds the IEC 61036 Class 1

specification.

The integrated circuit includes all the required functions for

single phase power and energy measurement. Two A/D

converters sample the voltage and current inputs. The

calculations required for power and energy are performed

and pulses on the LED, MON and MOP outputs represent the

results.

Internal offsets are eliminated through the use of cancellation

techniques. The SA4101A generates pulses at a frequency

that is proportional to the power consumption. Complimentary

output pins MOP and MON are provided for driving a stepper

motor. A MOP pulse followed immediately by a MON pulse

represents an energy pulse. This minimizes the risk of (after

power up) losing the first energy pulse as a result of the

stepper motor residing in the wrong phase.

The LED output is normally proportional to the average power

consumption measured. When in FAST mode, the LED

output is proportional to the instantaneous active power

consumption. The FAST mode is intended for meter

calibration purposes.

The two A/D converters convert the signals on the voltage

and current sense inputs to a digital format for further

processing. The current sense inputs (IIP and IIN) are

identical and balanced. An input signal with a range of 1:500

is measured at these inputs.

An integrated anti-creep function prevents any output pulses

if the measured power is less than 0.02% of the meter

’s rated

current.

The two digital signals, accurately representing the current

and voltage inputs, are multiplied using digital multiplication.

The output of the multiplier is the instantaneous power. For

voltage and current in phase instantaneous power is

calculated by:

����(����) = ����(����) × ����(����)

Let

√2

and

√2

then

where

p(t) is the instantaneous power,

v(t) is the instantaneous voltage signal,

i(t) is the instantaneous current signal,

This instantaneous power is then integrated over time to

provide the average power information:

���� =

1

����

∫ ����(����)��������

����

0

where

P is the average power and

cos

Analog Input Configuration

The input circuitry of the current and voltage sensor inputs is

illustrated in Figure 5.

Figure 5: Analog input configuration

These inputs are protected against electrostatic discharge

through clamping diodes.

A

I

IIN

IIP

VDD

VSS

VDD

VSS

A

V

IVP

VDD

VSS

AGND

VOLTAGE

SENSOR

INPUT

CURRENT

SENSOR

INPUT

CURRENT

CHANNEL

ADC

VOLTAGE

CHANNEL

ADC