MAXQ3180-RAN+ datasheet(63/101 Pages) MAXIM

63 / 101 page

Low-Power, Multifunction, Polyphase AFE

______________________________________________________________________________________

EOVF: Energy overflow. This flag indicates that one or

more energy accumulators (X.EAPOS, X.EANEG, etc.)

have overflowed. In a traditional meter, the host

processor would poll the MAXQ3180 to determine

which of the energy accumulators have overflowed and

adjust its internal accounting registers accordingly.

OC: The RMS current value on one or more of the

phases over the most recent DSP cycle has exceed-

ed the value set in the OCLVL register.

OV: The RMS voltage on one or more of the phases

over the most recent DSP cycle has exceeded the

value set in the OVLVL register.

UV: The RMS voltage on one or more of the phases

over the most recent DSP cycle has failed to exceed

the value set in the UVLVL register.

NOZX: Zero crossings were not detected on one or

more of the phases. The detection time is defined in

the NZX_TIMO register. The resolution for the

NZX_TIMO register is the duration of one ADC sam-

ple time (nominally 40μs).

DCHA: Tells the host processor that the direction of

net real energy flow on one of the three phases has

changed during the current DSP cycle as compared

to the previous DSP cycle.

DCHR: Tells the host processor that the direction of

net reactive energy flow on one of the three phases

has changed during the current DSP cycle as com-

pared to the previous DSP cycle.

DSPRDY: Indicates the latest DSP cycle has just

completed.

DSPOR: Indicates that the processing for the previ-

ous DSP cycle had not been completed before the

current DSP cycle became available for processing.

This overflow indication should never be seen in the

default configuration; however, under some condi-

tions (faster ADC rate, slower CPU clock) the pro-

cessing requirements may exceed the number of

CPU cycles available for DSP processing. Under

these circumstances, the clock rate may be

increased, the ADC rate may be reduced (that is,

the R_ADCRATE register may be increased), or the

functional load (such as fundamental mode calcula-

tions) may be cut.

Note that when DSPOR becomes set, all DSP calcu-

lations as well as all pulse outputs are invalidated.

The appropriate host response is to take the remedi-

al action described above and discard the current

set of DSP result values.

Each phase has a local register that contains copies of

the OC, OV, UV, NOZX, DCHA, and DCHR bits. Thus,

to determine which phase(s) have exception conditions

requires four reads: the IRQ_FLAG register to deter-

mine which conditions are active that are causing the

interrupt to occur, and then a read to A.FLAGS,

B.FLAGS, and C.FLAGS to determine which of the

phases have the indicated condition.

Finally, each phase has a pair of local registers that

contain overflow flags for each energy accumulator. If

the EOVF bit is set in the IRQ_FLAG register, the host

should then read the A.EOVER, B.EOVER, and

C.EOVER registers to determine which of the phases

have overflow conditions. If fundamental mode opera-

tion is enabled, the host should read A.EFOVER,

B.EFOVER, and C.EFOVER as well. Each of these reg-

isters contains a bit for each of real and reactive energy

in both positive and negative direction as well as

apparent energy.

Overvoltage and Overcurrent Detection

The MAXQ3180 detects overvoltage and overcurrent

events and can issue interrupt request signals to the

master when these events occur. The overvoltage level

can be programmed into the OVLVL register, while the

overcurrent level is determined by the OCLVL register.

Both OVLVL and OCLVL registers represent the bits

23:8 of the VRMS or IRMS registers. Any time the

MAXQ3180 detects the RMS-value exceeding a thresh-

old level, the OV or OC interrupt flag is set. If enabled,

any of these flags issues an interrupt request. All inter-

rupt flags are “sticky” bits—the MAXQ3180 never

clears them on its own unless a reset occurs. The inter-

rupt flags should be cleared by the master by writing

the appropriate register.

Meter Units to Real Units Conversion

All energy calculations, including various threshold

checks, are performed internally in fixed format in meter

units. Therefore, the threshold values must be supplied

by the user in meter units as well. This section summa-

rizes how to convert real units (V, A, kWh, W, and kAh)

into meter units and vice versa.

The conversion factors are based on the settings of tFR,

VFS, and IFS, defined by the user’s design.

tFR is analog scan frame timing. This parameter is

defined by the R_ADCRATE setting and system clock

frequency fSYS:

tFR = (R_ADCRATE + 1) x 8/fSYS

Default conditions are R_ADCRATE = 319, fSYS = 8MHz.

MAXQ3180-RAN+ датащи(PDF) 63 Page - Maxim Integrated Products

MAXQ3180-RAN+ датащи(HTML) 63 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 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 ...More

датащи скачать

ссылки URL