ADE9078ACPZ datasheet(67/108 Pages) AD

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ADE9078

Data Sheet

Rev. 0 | Page 66 of 107

WAVEFORM BUFFER

The ADE9078 has a waveform buffer comprised of 2048, 32-bit

memory locations with addresses from Address 0x800 to

Address 0xFFF. This memory can be filled with samples from

the sinc4 or sinc4 + IIR LPF or current and voltage waveform

samples processed by the digital signal processor.

Resampled waveforms make it easy to perform harmonic analysis

in an external processor that can use the 16-bit, 64 points per

line cycle samples directly in a FFT, without having to perform

any windowing functions.

The data in the waveform buffer can come from four locations

in the signal chain, as follows:



Sinc4 outputs, xI_SINC_DAT, xV_SINC_DAT: 16 kSPS



Sinc4 + IIR LPF output, xI_LPF_DAT, xV_LPF_DAT: 4 kSPS



Current and voltage channel waveforms processed by the

DSP (xI_PCF, xV_PCF): 4 kSPS



Resampled waveforms with 64 points per line cycle

processed by the DSP: data rate varies with line period

Figure 104 and Figure 105 show the current and voltage channel

datapaths, indicating which waveforms can be stored into the

waveform buffer.

Filling and accessing of the waveform buffer depends on which

type of data is being filled in the buffer. The waveforms with a

fixed data rate, 16 kSPS or 4 kSPS, are referred to as fixed data

rate waveforms. The following sections explain what modes/access

are available for resampled waveforms versus fixed data rate

waveforms.

The waveform buffer samples can be accessed using the SPI

burst read functionality so that multiple samples can be read

using only one SPI command header (see the Burst Read

Waveform Buffer Samples from SPI section).

xIGAIN

HPF

CURRENT PEAK

DETECTION

REFERENCE

Σ-∆

MODULATOR

VIN

+1V

ANALOG INPUT RANGE

–1V

ADE9078 CURRENT CHANNEL (IA, IB, IC)

SINC4

LPF

4:1

xIGAINx

PHASE

COMP

WAVEFORM

BUFFER

INTEGRATOR

WF_SRC

WF_CAP_SEL

MTEN

HPFDIS

INTEN

ICONSEL*

IB = –IA – IC

xI_PCF

RESAMPLING

ADC_

REDIRECT

MUX

NOTE: ICONSEL ONLY AFFECTS IB CHANNE L CALCULATION

TOTAL ACTIVE AND

REACTIVE POWER

CALCULATION

ZX_SRC_SEL

ZX DETECTION

NOT AVAILABLE IN ADE9078 PSM1

TOTAL CURRENT RMS

VA POWER

CALCULATIONS

FUNDAMENTAL

REACTIVE POWER

CALCULATIONS

RESAMPLED WAVEFORM

DATA RANGE

0xFBFF_FB90 =

–67,110,000

0x0471_15C0 =

+74,520,000

0x0474_E650 =

+74,770,000

CURRENT CHANNEL (xI_PCF)

DATA RANGE

SINC4 + IIR LPF (xI_LPF_DAT)

DATA RANGE

SINC4 OUTPUT (xI_SINC_DAT)

DATA RANGE

0x0400_0470 =

+67,110,000

0x46B4 =

+18,100

0xB94C =

–18,100

0xFB8B_19B0 =

–74,770,000

0xFB8E_EA40 =

–74,520,000

4kSPS

Figure 104. Current Channel Datapath

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