ADE9078ACPZ datasheet(31/108 Pages) AD

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ADE9078

Data Sheet

Rev. 0 | Page 30 of 107

It is also possible to use the current channel gain register to

change the sign of the current channel, which may be useful if

the current sensor was installed backwards. To compensate for

this situation, use current channel gain = −1.

xIGAIN = round((−1 − 1) × 227) = −268,435,456 =

0xF000 0000

If the multipoint gain and phase feature is used, it is

recommended to use the xIGAIN for the main correction,

performed at the nominal current for the meter (see the

Multipoint Gain and Phase Calibration section for more

information).

Note that for a given phase,

|Current Channel Gain × Voltage Channel Gain ×

Power Gain| ≤ 3.75

IB Calculation Using ICONSEL

Write the ICONSEL bit in the ACCMODE register to calculate

IB = −IA − IC. This setting can help save the cost of a current

transformer in some 3-wire delta configurations. See the Applying

the ADE9078 to a 3-Wire Delta Service section for more

information.

High-Pass Filter

A high-pass filter is provided to remove dc offsets for accurate

rms and energy measurements.

The ADE9078 high-pass filter on the current and voltage channels

is enabled by default. It can be disabled by writing the DISPHPF bit

in the CONFIG0 register = 1.

It is recommended to leave the high-pass filter enabled to achieve

the metering performance listed in the specifications in Table 1.

For some applications, it is desirable to increase the high-pass

filter corner, such as to improve performance when a Rogowski

coil current sensor is used.

The high-pass filter corner is selectable using the HPF_CRN bits in

the CONFIG2 register.

Table 10. HPF Corner Gain with 50 Hz Input Signal

HPF_

CRN

f−3 dB

(Hz)

HPF_

GAIN

Settling Time

to 1% for DC

Step (sec)

Settling Time

to 0.1% for DC

Step (sec)

38.7

0.80

0.0178

0.0268

19.6

0.94

0.0363

0.0544

9.90

0.99

0.0731

0.1097

4.97

1.00

0.1468

0.2202

2.49

1.00

0.2942

0.4412

1.25

1.00

0.5889

0.8833

6 (default)

0.625

1.00

1.1784

1.7675

0.313

1.00

2.3573

3.5359

Digital Integrator

A digital integrator is included to allow easy interfacing to di/dt

current sensors, also known as Rogowski coils. The di/dt sensor

output increases 20 dB/decade over the frequency range. To

compensate for this increased output, the digital integrator applies

−20 dB/decade gain with a phase shift of approximately −90°.

A second-order antialiasing filter is required to avoid noise

aliasing back in the band of interest when the ADC is sampling.

To enable the digital integrator on the IA, IB, and IC channels,

set the INTEN bit in the CONFIG0 register. To enable the digital

integrator on the neutral current, IN channel, set the ININTEN bit

in the CONFIG0 register.

Figure 44 through Figure 47 show the magnitude and phase

response of the ADE9078 digital integrator with the

recommended DICOEFF value of 0xFFFFE000.

FREQUENCY (Hz)

–150

0.1

100

–100

–50

Figure 44. Digital Integrator Magnitude Response, DICOEFF = 0xFFFFE000

FREQUENCY (Hz)

400

800

1200

1600

2000

Figure 45. Digital Integrator Phase Response, DICOEFF = 0xFFFFE000

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