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4/14

PRELIMINARY

PM4301APDA

R24

R21

IVP1

GND

C7

R20

R19

GND

V

NOM

(220V / 110V)

(11µA

Phase 1

Neutral

GND

R23

P1

SA4301A

SA9105G

AGND

JS4 “V1”

JS4 “N”

R22

GND

J1

110V / 220V

R24

R21

IVP1

GND

C7

R20

R19

GND

V

NOM

(220V / 110V)

(11µA

Phase 1

Neutral

GND

R23

P1

SA4301A

SA9105G

AGND

JS4 “V1”

JS4 “N”

R22

GND

J1

110V / 220V

Figure 3: Voltage channel 1 input network on the PM4301APDA

Low-pass filters are required on the voltage sense inputs to

remove any high frequency signals that could affect the

performance of the SA4301A/SA9105G. The phase shift of

the current transformers is compensated by means of these

low-pass filters as well, by purposefully increasing the cut-

off frequency.

Referring to Figure 3, the capacitor C7 is used to both

implement the high frequency filtering as well as

compensating for any phase shift caused by the current

transformer. The cut-off frequency of the filter is adjusted so

that the phase shift of the voltage input network is identical

to the sum of the phase shifts of the current transformer and

the current input network. The PM4301APDA module has

been set up to compensate for a phase shift of 0.09 degrees

at 50Hz. This can be changed by changing the capacitors

on the voltage input networks (C7, C8, C9). The new

capacitor value can be calculated by adapting the following

calculation as required.

The phase shift of the current input network is

rees

deg

297

.

0

)

Hz

50

C

R

arctan(

C

C

II

-

»

´

p

-

=

f

The phase shift required on the voltage input networks is

therefore

207

.

0

09

.

0

297

.

0

CT

II

IV

-

=

+

-

=

f

+

f

=

f

where

is typically between about 0.05 degrees and 0.5 degrees for

a good quality current transformer. Neglecting R19, R20,

R21, R22 and R24 because all these resistors are

significantly larger than P1 and R23, the capacitance

required to achieve the -0.207 degree phase shift is

nF

6

.

5

Hz

50

)

23

R

1

P

(

2

tan

7

C

IV

»

´

+

p

f

=

resulting in a cut-off frequency of

kHz

7

.

13

7

C

)

23

R

1

P

(

2

1

»

´

+

p

=

.

The value of the cut-off frequency of the voltage input

network is less critical than that of the current input networks

because the dynamic range of the voltage input is small. A

cut-off frequency between 10kHz and 25kHz is acceptable.

POWER SUPPLY

The PM4301APDA has an on-board filtered voltage divider

to allow the evaluation board to be used with a single 5V

supply. The ground level GND which represents the

reference level of the meter (connected to NEUTRAL of the

mains voltage) can be generated by the on-board voltage

divider. This level is also connected to the AGND pin of the

energy metering device. If the module is used in conjunction

with a dual 2.5V supply then the on-board voltage divider is

simply overdriven by the external supply. The centre point of

the split supply is the reference level of the energy meter.

REFERENCE VOLTAGE

The on-chip reference currents of the SA4301A/SA9105G

are determined by the bias resistor R37. This resistor must

be 47k

W to set optimum bias conditions for the analog

circuits of the energy metering device.

LED OUTPUTS

The PM4301APDA is equipped with LEDs to display the

various outputs of the SA4301A/SA9105G. These are the

pulse output and the per phase mains voltage and direction

indicators. The LEDs can be disconnected if not required.

TESTPOINTS

Test points for several signals are located on the

PM4301APDA evaluation board. These test points allow

certain critical signals on the current and voltage input

networks to be measured. Test points for the meter

reference level (GND) and the power supplies are also

present.