ADE7880 datasheet(67/104 Pages) AD

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Data Sheet

ADE7880

Rev. A | Page 67 of 104

The CFx pulse output is active low and preferably connected to

an LED, as shown in Figure 88.

VDD

CFx PIN

Figure 88. CFx Pin Recommended Connection

Bits[11:9] (CF3DIS, CF2DIS, and CF1DIS) of the CFMODE

the CF3, CF2, or CF1 pin. When Bit CFxDIS is set to 1 (the

default value), the CFx pin is disabled and the pin stays high.

When Bit CFxDIS is cleared to 0, the corresponding CFx pin

output generates an active low signal.

Bits[16:14] (CF3, CF2, CF1) in the Interrupt Mask register

MASK0 manage the CF3, CF2, and CF1 related interrupts.

When the CFx bits are set, whenever a high-to-low transition at

the corresponding frequency converter output occurs, an

interrupt IRQ0 is triggered and a status bit in the STATUS0

output is not enabled by the CFxDIS bits in the CFMODE

Synchronizing Energy Registers with CFx Outputs

The ADE7880 contains a feature that allows synchronizing the

content of phase energy accumulation registers with the

generation of a CFx pulse. When a high-to-low transition at one

frequency converter output occurs, the content of all internal

phase energy registers that relate to the power being output at

CFx pin is latched into hour registers and then resets to 0.

See Table 23 for the list of registers that are latched based on

the CFxSEL[2:0] bits in the CFMODE register. All 3-phase

registers are latched independent of the TERMSELx bits of the

COMPMODE register. The process is shown in Figure 89 for

CF1SEL[2:0] = 010 (apparent powers contribute at the CF1 pin)

and CFCYC = 2.

The CFCYC 8-bit unsigned register contains the number of

high to low transitions at the frequency converter output between

two consecutive latches. Avoid writing a new value into the

CFCYC register during a high-to-low transition at any CFx pin.

CFCYC = 2

AVAHR, BVAHR,

CVAHR LATCHED

ENERGY REGISTERS

RESET

AVAHR, BVAHR,

CVAHR LATCHED

ENERGY REGISTERS

RESET

CF1 PULSE

BASED ON

PHASE A AND

PHASE B

APPARENT

POWERS

Figure 89. Synchronizing AVAHR and BVAHR with CF1

Bits[14:12] (CF3LATCH, CF2LATCH, and CF1LATCH) of the

CFMODE register enable this process when set to 1. When

cleared to 0, the default state, no latch occurs. The process is

available even if the CFx output is not enabled by the CFxDIS

bits in the CFMODE register.

Energy Registers and CF Outputs for Various

Accumulation Modes

Bits[1:0] (WATTACC[1:0]) in the ACCMODE register deter-

mine the accumulation modes of the total and fundamental active

powers when signals proportional to the active powers are chosen

at the CFx pins (the CFxSEL[2:0] bits in the CFMODE register

equal 000 or 011). They also determine the accumulation modes

of the watt-hour energy registers (AWATTHR, BWATTHR,

CWATTHR, AFWATTHR, BFWATTHR and CFWATTHR).

When WATTACC[1:0] = 00 (the default value), the active powers

are sign accumulated in the watt-hour registers and before entering

the energy-to-frequency converter. Figure 90 shows how signed

active power accumulation works. In this mode, the CFx pulses

synchronize perfectly with the active energy accumulated in

xWATTHR registers because the powers are sign accumulated in

both data paths.

NEG

POS

APNOLOAD

SIGN = POSITIVE

NEG

NO-LOAD

THRESHOLD

ACTIVE POWER

NO-LOAD

THRESHOLD

ACTIVE ENERGY

REVAPx BIT

IN STATUS0

xWSIGN BIT

IN PHSIGN

Figure 90. Active Power Signed Accumulation Mode

When WATTACC[1:0] = 01, the active powers are accumulated

in positive only mode. When the powers are negative, the watt-

hour energy registers are not accumulated. CFx pulses are

generated based on signed accumulation mode. In this mode,

the CFx pulses do not synchronize perfectly with the active

energy accumulated in xWATTHR registers because the powers are

accumulated differently in each data path. Figure 91 shows how

positive only active power accumulation works.

WATTACC[1:0] = 10 setting is reserved and the ADE7880

behaves identically to the case when WATTACC[1:0] = 00.

When WATTACC[1:0] = 11, the active powers are accumulated

in absolute mode. When the powers are negative, they change

sign and accumulate together with the positive power in the

watt-hour registers and before entering the energy-to-frequency

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