ADE7755AN-REF Просмотр технического описания (PDF) - Analog Devices

Номер в каталоге

Компоненты Описание

производитель

ADE7755AN-REF

Energy Metering IC with Pulse Output

Analog Devices 

ADE7755

Pin No. Mnemonic

21

DGND

22

23, 24

CF

F2, F1

Description

This provides the ground reference for the digital circuitry in the ADE7755, i.e., multiplier, filters, and

digital-to-frequency converter. This pin should be tied to the digital ground plane of the PCB. The

digital ground plane is the ground reference for all digital circuitry, e.g., counters (mechanical and

digital), MCUs, and indicator LEDs. For good noise suppression, the analog ground plane should

only be connected to the digital ground plane at one point only, e.g., a star ground.

Calibration Frequency Logic Output. The CF logic output gives instantaneous real power informa-

tion. This output is intended to be used for calibration purposes. Also see SCF Pin description.

Low Frequency Logic Outputs. F1 and F2 supply average real power information. The logic outputs

can be used to directly drive electromechanical counters and two phase stepper motors. See Transfer

Function section.

TERMINOLOGY

MEASUREMENT ERROR

The error associated with the energy measurement made by the

ADE7755 is defined by the following formula:

Percentage

Error

=

Energy

Registered

by the ADE7755

True Energy

– True

Energy

¥ 100%

PHASE ERROR BETWEEN CHANNELS

The HPF (High-Pass Filter) in Channel 1 has a phase lead

response. To offset this phase response and equalize the phase

response between channels, a phase correction network is also

placed in Channel 1. The phase correction network matches the

phase to within ± 0.1∞ over a range of 45 Hz to 65 Hz and ± 0.2∞

over a range 40 Hz to 1 kHz. See Figures 4 and 5.

POWER SUPPLY REJECTION

This quantifies the ADE7755 measurement error as a percent-

age of the reading when the power supplies are varied.

For the ac PSR measurement, a reading at nominal supplies

(5 V) is taken. A 200 mV rms/100 Hz signal is then introduced

onto the supplies and a second reading obtained under the same

input signal levels. Any error introduced is expressed as a

percentage of the reading (see Measurement Error definition).

For the dc PSR measurement, a reading at nominal supplies

(5 V) is taken. The supplies are then varied ± 5% and a second

reading is obtained with the same input signal levels. Any error

introduced is again expressed as a percentage of the reading.

ADC OFFSET ERROR

This refers to the dc offset associated with the analog inputs to

the ADCs. It means that with the analog inputs connected to

AGND, the ADCs still see a small dc signal (offset). The offset

decreases with increasing gain in Channel V1. This specification

is measured at a gain of 1. At a gain of 16, the dc offset is typi-

cally less than 1 mV. However, when the HPF is switched on,

the offset is removed from the current channel and the power

calculation is not affected by this offset.

GAIN ERROR

The gain error of the ADE7755 is defined as the difference between

the measured output frequency (minus the offset) and the ideal

output frequency. It is measured with a gain of 1 in Channel V1.

The difference is expressed as a percentage of the ideal frequency.

The ideal frequency is obtained from the ADE7755 transfer

function (see Transfer Function section).

GAIN ERROR MATCH

The gain error match is defined as the gain error (minus the off-

set) obtained when switching between a gain of 1 and a gain of 2,

8, or 16. It is expressed as a percentage of the output frequency

obtained under a gain of 1. This gives the gain error observed

when the gain selection is changed from 1 to 2, 8, or 16.

–6–

REV. 0

Share Link: