ADE7912 datasheet(22/41 Pages) AD

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ADE7912/ADE7913

Data Sheet

Rev. C | Page 22 of 41

ADE7912/ADE7913 STATUS

The bits in the STATUS0 and STATUS1 registers of the

ADE7912/ADE7913 characterize the state of the device.

If the value of the CTRL_CRC register changes, Bit 1 (CRC_STAT)

is set to 1 in the STATUS0 register. This bit clears to 0 when the

STATUS0 register is read.

After the configuration registers are protected by writing 0xCA

into the lock register, Bit 2 (IC_PROT) in the STATUS0 register

is set to 1. It clears to 0 when the STATUS0 register is read, and

it is set back to 1 at the next ADC output cycle.

At power-up, or after a hardware or software reset, the

ADE7912/ADE7913 signal the end of the reset period by

clearing Bit 0 (RESET_ON) to 0 in the STATUS0 register.

If the ADC output values of IWV, V1WV, and V2WV are not

read during an output cycle, Bit 3 (ADC_NA) in the STATUS1

read.

The STATUS0 and STATUS1 registers can be read by executing

an SPI register read. STATUS0 can also be read as part of the

SPI burst mode read operation. See the SPI Read Operation and

the SPI Read Operation in Burst Mode sections for more

information.

INSULATION LIFETIME

All insulation structures eventually break down when subjected

to voltage stress over a sufficiently long period of time. The rate

of insulation degradation is dependent on the characteristics of

the voltage waveform applied across the insulation. In addition

to the testing performed by the regulatory agencies, Analog

Devices carries out an extensive set of evaluations to determine

the lifetime of the insulation structure within the ADE7912/

ADE7913 devices. Analog Devices performs accelerated life

testing using voltage levels higher than the rated continuous

working voltage. Acceleration factors for several operating

conditions are determined. These factors allow calculation of

the time to failure at the actual working voltage.

The values shown in Table 8 summarize the maximum working

voltage for 50 years of service life for a bipolar ac operating

condition. In many cases, the approved working voltage is

higher than the 50-year service life voltage. Operation at these

high working voltages can lead to shortened insulation life in

some cases.

The insulation lifetime of the ADE7912/ADE7913 devices

depends on the voltage waveform type imposed across the

isolation barrier. The iCoupler insulation structure degrades at

different rates depending on whether the waveform is bipolar ac

or dc. Figure 30 and Figure 31 illustrate these different isolation

voltage waveforms.

Bipolar ac voltage is the most stringent environment. The goal

of a 50-year operating lifetime under the bipolar ac condition

determines the maximum working voltage recommended by

Analog Devices. In the case of dc voltage, the stress on the

insulation is significantly lower. This allows operation at higher

working voltages while still achieving a 50-year service life.

The working voltages listed in Table 8 can be applied while

maintaining the 50-year minimum lifetime, provided that the

voltage conforms to the dc voltage case. Treat any cross-insulation

voltage waveform that does not conform to Figure 31 as a bipolar

ac waveform, and limit the peak voltage to the 50-year lifetime

voltage value listed in Table 8.

RATED PEAK VOLTAGE

Figure 30. Bipolar AC Waveform

RATED PEAK VOLTAGE

Figure 31. DC Waveform

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