ADE75 datasheet(46/148 Pages) AD

46 / 148 page

Preliminary Technical Data

ADE75xx/ADE71xx

Rev. PrE | Page 46 of 148

x1, x2, x4,

x8, x16

ANALOG

INPUT

RANGE

HPF

ADC

REFERENCE

0.5V, 0.25V,

0.125V, 62.5mV,

31.3mV

WAVEFORM SAMPLE

VOLTAGE RMS (VRMS)

CALCULATION

PGA2

{GAIN[7:5]}

VOLTAGE CHANNEL

WAVEFORM

DATA RANGE

0xD70B

0x0000

0x28F5

ACTIVE AND REACTIVE

POWER CALCULATION

LPF1

f–3dB = 63.7Hz

MODE1[6]

ZX SIGNAL

DATA RANGE for 60Hz signal

0xE230

0x0000

0x1DD0

ZX DETECTION

ZX SIGNAL

DATA RANGE for 50Hz signal

0xDFC9

0x0000

0x2037

VOLTAGE PEAK DETECT

Figure 22. ADC and Signal Processing in Voltage Channel

Channel Sampling

The waveform samples of the current ADC and voltage ADC

can also be routed to the waveform registers to be read by the

MCU core. The active, reactive, apparent power, and energy

calculation remain uninterrupted during waveform sampling.

When in waveform sampling mode, one of four output sample

rates can be chosen by using Bits 0 and 1 of the WAVMODE

12.8kSPS, 6.4 kSPS, or 3.2 kSPS—see Table 31. If the WFSM

enable bit is set in the Interrupt Enable Register 3 SFR

(MIRQENH, 0xDB), the 8052 core has a pending ADE

interrupt. The sampled signals selected in the WAVMODE

waveform high byte (WAV1H or WAV2H) is read.

The ADE interrupt stays active until the WFSM status bit is

cleared—see Energy measurement interrupts section.

FAULT DETECTION13

The ADE75xx/ADE71xx incorporates a fault detection scheme

that warns of fault conditions and allows the

ADE75xx/ADE71xx to continue accurate measurement during

a fault event. The ADE75xx/ADE71xx does this by continuously

monitoring both current inputs (IA and IB). These currents will

be referred for ease of understanding as phase and neutral

(return) currents. In the ADE75xx/ADE71xx, a fault condition

is defined when the difference between IA and IB is greater than

13 This function is not available in ADE7566 and ADE7569 products.

6.25% of the active channel. If a fault condition is detected and

the inactive channel is larger than the active channel, the

ADE75xx/ADE71xx automatically switches to current

measurement to the inactive channel. During a fault, the active,

reactive, current rms and apparent powers are generated using

the larger of the two currents. On power-up, IA is the current

input selected for Active, Reactive, and Apparent power and

Irms calculations.

To prevent false alarm, averaging is done for the fault detection

and a fault condition is detected approximately 1 second after

the event. The fault detection is automatically disabled when the

voltage signal is less than 0.3% of the full-scale input range. This

eliminates false detection of a fault due to noise at light loads.

Because the ADE75xx/ADE71xx looks for a difference between

the voltage signals on IA and IB, it is important that both current

transducers be closely matched.

Channel selection Indication

The current channel selected for measurement is indicated by

bit 7 (ICHANNEL) in the ACCMODE register (0x0F). When

this bit is cleared, IA is selected and when it is set, IB is selected.

The ADE75xx/ADE71xx automatically switches from one

channel to the other and reports the channel configuration in

the ACCMODE register (0x0F).

The current channel selected for measurement can also be

forced. Setting one of the SELCH1A and SELCH1B bits in the

CALMODE register (0x3D) selects IA and IB respectively. When

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