ADE7754 datasheet(15/44 Pages) AD

15 / 44 page

REV. PrG 01/03

PRELIMINARY TECHNICAL DATA

ADE7754

– 15 –

PEAK DETECTION

The ADE7754 can also be programmed to detect when the

absolute value of the voltage or the current channel of one

phase exceeds a certain peak value. Figure 15 illustrates the

behavior of the PEAK detection for the voltage channel.

VPEAK[7:0]

VAP, VBP, or VCP

PKV Interrupt Flag

(Bit C of STATUS register)

PKV reset low

when RSTATUS register

is read

Read RSTATUS register

Figure 15 - ADE7754 Peak detection

Bits 2-3 of the Measurement Mode register define the phase

supporting the peak detection. Both current and voltage of

this phase can be monitored at the same time. Figure 15

shows a line voltage exceeding a threshold which is set in the

Voltage peak register (VPEAK[7:0]). The Voltage Peak

event is recorded by setting the PKV flag in the Interrupt

Status register. If the PKV enable bit is set to logic one in the

Interrupt Mask register, the IRQ logic output will go active

low - see ADE7754 Interrupts.

Peak Level Set

The contents of the VPEAK and IPEAK registers are respec-

tively compared to the absolute value of the most significant

byte output of the selected voltage and current channels.

Thus, for example, the nominal maximum code from the

current channel ADC with a full scale signal is 28F5C2h —

see Current Channel Sampling.

Therefore, writing 28h to the IPEAK register will put the

current channel peak detection level at full scale and set the

current peak detection to its least sensitive value.

Writing 00h will put the current channel detection level at

zero. The detection is done when the content of the IPEAK

TEMPERATURE MEASUREMENT

The ADE7754 also includes an on-chip temperature sensor.

A temperature measurement is made every 4/CLKIN sec-

onds. The output from the temperature sensing circuit is

connected to an ADC for digitizing. The resultant code is

processed

and

placed

the

Temperature

(TEMP[7:0]). This register can be read by the user and has

an address of 08h -see ADE7754 Serial Interface section.

The contents of the Temperature register are signed (2's

complement) with a resolution of 4°C/LSB. The tempera-

ture register will produce a code of 00h when the ambient

temperature is approximately 129°C. The value of the

will be : Temperature register = (Temperature (°C)

- 129)/4.

The temperature in the ADE7754 has an offset tolerance of

approximately ±5°C. The error can be easily calibrated out

by an MCU.

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