REV. PrB 08/01

–9–

PRELIMINARY TECHNICAL DATA

ADE7752

()

()









+

⋅

⋅

⋅

















+

⋅

⋅

−









+

⋅

⋅

+

⋅

⋅

⋅

















+

⋅

⋅

−

⋅

⋅

=

−

×

−

+

−

×

−

=

3

2

cos

2

3

4

cos

2

3

2

cos

2

cos

2

3

4

cos

2

cos

2

)

(

)

(

)

(

)

(

π

ω

π

ω

π

ω

ω

π

ω

ω

t

I

t

V

t

V

t

I

t

V

t

V

P

IBN

IBP

VC

VB

IAN

IAP

VC

VA

P

l

B

l

C

l

B

l

A

l

C

l

A

For simplification, we assume that

()

()









+

⋅

+

⋅









⋅

⋅

⋅

+

⋅









+

⋅









⋅

⋅

⋅

=

3

2

cos

sin

3

sin

2

cos

3

2

sin

3

2

sin

2

π

ω

π

ω

π

ω

π

ω

π

t

t

I

V

t

t

I

V

P

l

l

B

l

l

A

(9)

P then becomes:

















+

+









⋅

⋅

+





















+

+









⋅

⋅

=

3

2

sin

3

sin

3

2

2

sin

3

2

sin

π

ω

π

π

ω

π

t

I

V

t

I

V

P

l

B

BN

l

A

AN

(10)

Where:

π/3) represents the RMS voltage between

VAP and VN pins of the ADE7752

π/3) represents the RMS voltage between

VBP and VN pins of the ADE7752.

As the LPF on each channel eliminates the 2

ω

the equation, the Real power measured by the ADE7752 is:

2

3

2

3

⋅

⋅

+

⋅

⋅

=

B

BN

A

AN

I

V

I

V

P

Where:

the ADE7752 after voltage sensing

ADE7752 after current sensing

If full scale AC voltage of ±125 mV peak are applied to the

Voltage channels and Current channels, the expected output

frequency is calculated as follows:

= 0.596 Hz, SCF = S0 = S1 = 1

VAN = VBN = IA = IB

VCN = IC = 0

= 2.5 V (nominal reference value).

NOTE: If the on-chip reference is used, actual

output frequencies may vary from device to

device due to reference tolerance of ±8%.

14

.

0

2

3

5

.

2

2

2

596

.

0

125

.

0

125

.

0

2

.

109

2

2

=

×

×

×

×

×

×

×

=

Freq

Table III shows a complete listing of all maximum output

frequencies when using all three channels inputs.

Table III. Maximum Output Frequency on F1 and F2

Max Frequency

Max Frequency

SCF

S1

S0

for DC Inputs (Hz)

for AC Inputs (Hz)

1

1

1

0.48

0.24

0

1

1

62.52

31.26

-

1

0

15.6

7.8

-

0

1

3.9

1.95

-

0

0

0.96

0.48

Frequency Output CF

The pulse output CF (Calibration Frequency) is intended for

use during calibration. The output pulse rate on CF can be

up to 160 times the pulse rate on F1 and F2. The lower the

shows how the two frequencies are related, depending on the

states of the logic inputs S0, S1 and SCF. Because of its

relatively high pulse rate, the frequency at this logic output

is proportional to the instantaneous real power. As is the case

with F1 and F2, the frequency is derived from the output of

the low-pass filter after multiplication. However, because the

output frequency is high, this real power information is

accumulated over a much shorter time. Hence less averaging

is carried out in the digital-to-frequency conversion. With

much less averaging of the real power signal, the CF output

is much more responsive to power fluctuations—see Signal

Processing Block in Figure 8.

Table IV. Maximum Output Frequency on CF

SCF

S1

S0

CF Max for AC Signals (Hz)

0

0

0

1.19

160 x F1, F2 = 78.12

1

0

0

1.19

8 x F1, F2 = 3.90

0

0

1

4.77

160 x F1, F2 = 312.51

1

0

1

4.77

16 x F1, F2 = 31.26

0

1

0

19.07

16 x F1, F2 = 130.56

1

1

0

19.07

8 x F1, F2 = 62.49

0

1

1

76.29

8 x F1, F2 = 250

1

1

1

0.596

16 x F1, F2 = 3.90 Hz

Frequency Outputs

Figure 1 shows a timing diagram for the various frequency

outputs. The outputs F1 and F2 are the low frequency

outputs that can be used to directly drive a stepper motor or

electromechanical impulse counter. The F1 and F2 outputs

provide two alternating high going pulses. The pulsewidth

however the period of F1 and F2 falls below 550 ms (1.81 Hz)

the pulsewidth of F1 and F2 is set to half of their period. The

maximum output frequencies for F1 and F2 are shown in

Table III.

The high frequency CF output is intended to be used for

communications and calibration purposes. CF produces a

to active power. The CF output frequencies are given in

Table IV. As in the case of F1 and F2, if the period of CF

period. For example, if the CF frequency is 20 Hz, the CF

pulsewidth is 25 ms.