SPEC-3093 (REV. 2)

8/15

29-09-2017

SA4305A

feature improves the device performance in missing phase

scenarios. It also allows the device to be used in three phase

three wire meters where one channel of the device is unused.

Reverse Energy Flow Indication

The SA4305A assesses the phase difference between the

voltage and current channel signals to determine the direction

of energy flow. If the overall energy flow is negative the

reverse energy indicator is activated. This facility is designed

to detect the wrongful connection or possible tampering of the

meter. If the adder is programmed to absolute mode the

energy flow direction information is lost. The operation of the

direction output is fully described in the Output Signals

section.

Starting Current

The SA4305A generates pulses on the pulse outputs for an

with the IEC requirement where the meter is required to

generate pulses for currents greater than 0.4%Ib.

Power-On Reset

The SA4305A has a power-on reset circuitry that activates

whenever the voltage between VDD and VSS is less than

3.6V ± 8%.

Power Consumption

The power consumption of the SA4305A integrated circuit is

less than 50mW.

Compatibility with SA2005F

The SA4305A can be used as a functionally compatible

replacement for the SA2005F by simply leaving the pins FPM

and MS unconnected. It should however be noted that the

value of the reference resistor on the VREF pin has to be

changed from 24k

 to 47k

INPUT SIGNALS

Voltage Reference (VREF)

A bias resistor of 47k

 sets optimum bias and reference

conditions on chip. Calibration of the SA4305A should be

done on the voltage inputs and not on the VREF input.

Current Sense Inputs (IIP1/IIN1, IIP2/IIN2, IIP3/IIN3)

Figure 6 shows the typical connections for the current sensor

input for one channel. The circuit has to be repeated for the

the resistor values should be selected for input currents of

headroom until saturation occurs.

The resistors RA and RB form the current transformers

termination resistor. The reference level is connected in the

centre of the termination resistor to achieve purely differential

input currents. The voltage drop across the termination

also be significantly smaller than the DC resistance of the

current transformers secondary winding.

Figure 6: Current sense input configuration

The resistors R1 to R4 define the current flowing into the

device. For best performance the SA4305A requires anti-

alias filters on the current sense inputs. These filters are

realized by means of the capacitors C1 and C2. The typical

cut-off frequency of these filters should be between 10kHz

and 20kHz. The optimum input network is achieved by setting

This sets the equivalent resistance associated with each

Voltage Sense Inputs (IVP1, IVP2, IVP3)

Figure 7 shows the voltage sense input configuration for one

channel. The circuit is identical for the other two channels.

The voltage sense input saturates at an input current of

input should be set at 14

without saturating the voltage sense input.

Figure 7: Voltage sense input configuration

For best performance the SA4305A also requires an anti-

alias filter on the voltage sense inputs. Referring to Figure 7,

the capacitor C1 is used to both implement the anti-alias filter

as well as compensating for any phase shift caused by the

current transformer. The resistor R4 defines the input current

into the device. The optimum input network is achieved by

setting R4 in the order of 100k

. If R4 is made too large the

capacitor C1 will be very small and the accuracy of the phase

R3

R1

RA

IIN

IIP

GND

CT1

Current In

I

MAX

16µA

RMS

R4

R2

RB

Current Out

C1

C2

R4

R3

IVP

GND

C1

R2

R1

GND

V

NOM

14µA

RMS

Voltage In

Neutral

GND

R5

P1

(P1 + R5) << R4 << (R1 + R2 + R3)