MAXQ3181-RAN+ datasheet(52/84 Pages) MAXIM

52 / 84 page

Low-Power, Active Energy, Polyphase AFE

______________________________________________________________________________________

tents of I1THR, then the angle expressed in PA0 is used

to compensate the phase angle. If the raw RMS current

is less than I2THR, then the angle expressed in PA2 is

used to compensate the phase angle. And if the raw

RMS current falls between I1THR and I2THR then PA1 is

used to compensate the phase angle. In this way, a

three-piece stepwise approximation of the phase

response of the current sensor is available.

To use a constant phase compensation, set I1THR and

I2THR to zero and insert the phase compensation value

into PA0.

Apparent energy is calculated as the product of the raw

RMS volts and amps.

Line Frequency: Line frequency can be taken directly

from the NS value. Recall that NS is the number of

frames in a DSP cycle. Since each frame is 320μs, sim-

ply multiply NS by 320μs and divide by CYCNT to

obtain the line period. The reciprocal of this is the line

frequency.

Energy Accumulation

Once real energy over the most recent DSP cycle has

been calculated, it is necessary to accumulate the

result.

The result accumulated during any DSP cycle can be

positive (that is, energy is delivered to the load) or neg-

ative (that is, energy is driven back into the line). These

values are separately accumulated.

Apparent energy is also accumulated, but since this

value is always positive or zero, there is only one

apparent energy accumulator.

From time to time, the accumulators generate an over-

flow. When this occurs, the appropriate bit is set in the

overflow status register X.EOVER.

When an overflow occurs, supervisory code running on

the host processor must make the appropriate adjust-

ments in the reported energy. In many cases, this could

simply involve incrementing an overflow counter. The

host processor must then clear the overflow indication.

No-Zero-Crossing Detection

The MAXQ3181 monitors the voltage signal on each

phase for zero-crossing events. If no ascending zero

crossings are detected within a specified number

(NZX_TIMO) of analog scan sample periods, the

NOZXF (X.FLAGS) flag is set by the MAXQ3181 to noti-

fy the master of this condition. If the NOZXM bit is set,

this flag sets the NOZX bit in the IRQ_FLAG. If the inter-

rupt enable bit ENOZX is set to 1, the interrupt signal

IRQ is driven low by the MAXQ3181 whenever NOZX =

1. The master can clear NOZXF and NOZX back to 0 to

remove the interrupt condition.

Phase Sequence Status

A phase sequence status bit PHSEQ indicates the

order in which zero crossings are detected. When a

zero-crossing event occurs on the phase A voltage sig-

nal, followed by phase B, phase C, and then phase A

I THR

PA I THR

I THR

RMS

≥

>≥

,,I

I THR

RMS <

⎧

⎨

⎪

⎩

⎪

⎫

⎬

⎪

⎭

⎪

AVERAGE

AVG_C

EAPPARENT

E_GAIN

APPSEL = 0

× Y

RAW_I

RAW_V

Figure 12. Apparent Energy Calculations

PHASE

COMPENSATION

PA0

PA1

PA2

LINEARIZATION

AVERAGE

AVG_C

EREAL

E_RAWREAL

OFFS_HI

GAIN_LO

OFFS_LO

E_GAIN

Figure 11. Phase Compensation for Energy Calculations

MAXQ3181-RAN+ 데이터시트(PDF) 52 Page - Maxim Integrated Products

MAXQ3181-RAN+ 데이터시트(HTML) 52 Page - Maxim Integrated Products

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84

데이터시트 다운로드

링크 URL