The ADE7978, the ADE7933/ADE7932, and ADE7923 form a
chipset dedicated to measuring 3-phase electrical energy using
shunts as current sensors.
The ADE7933/ADE7932 are isolated, 3-channel sigma-delta
analog-to-digital converters (Σ-Δ ADCs) for polyphase energy
metering applications that use shunt current sensors.
The
ADE7923 is a nonisolated, 3-channel Σ-Δ ADC for the neutral line
that uses a shunt current sensor. The ADE7932 features two ADCs,
and the ADE7933 and ADE7923 feature three ADCs.
One channel is dedicated to measuring the voltage across the
shunt when a shunt is used for current sensing. This channel
provides a signal-to-noise ratio (SNR) of 67 dB over a 3.3 kHz
signal bandwidth. Up to two additional channels are dedicated
to measuring voltages, which are usually sensed using resistor
dividers.
The unused voltage channels on the neutral ADE7923 can be
used for auxiliary voltage measurements. These channels provide
an SNR of 75 dB over a 3.3 kHz signal bandwidth. One voltage
channel can be used to measure the temperature of the die via
an internal sensor.
The ADE7933 and ADE7923 include three channels: one
current channel and two voltage channels. The ADE7932
includes one current channel and one voltage channel, but is
otherwise identical to the ADE7933.
The ADE7933/ADE7932 include isoPower®, an integrated,
isolated dc-to-dc converter. Based on the Analog Devices, Inc.,
iCoupler® technology, the dc-to-dc converter provides the
regulated power required by the first stage of the ADCs at a
3.3 V input supply. The ADE7933/ADE7932 eliminate the need
for an external dc-to-dc isolation block. The iCoupler chip scale
transformer technology is used to isolate the logic signals
between the first and second stages of the ADC. The result is a
small form factor, total isolation solution. The ADE7923 is the
nonisolated version of the ADE7933 that can be used for
neutral current measurement when isolation from the neutral
line is not required.
The ADE7933/ADE7932 and ADE7923 contain a digital interface
that is specially designed to interface with the ADE7978. Using
this interface, the ADE7978 accesses the ADC outputs and
configuration settings of the ADE7933/ADE7932 and
ADE7923.
The ADE7933/ADE7932 are available in a 20-lead, Pb-free, widebody
SOIC package with increased creepage. The ADE7923 is
available in a similar 20-lead, Pb-free, wide-body SOIC package
without the increased creepage.
The ADE7978 is a high accuracy, 3-phase electrical energy
measurement IC with serial interfaces and three flexible pulse
outputs. The ADE7978 can interface with up to four ADE7933/
ADE7932 and ADE7923 devices. The ADE7978 incorporates all
the signal processing required to perform total (fundamental and
harmonic) active, reactive, and apparent energy measurement
and rms calculations, as well as fundamental-only active and
reactive energy measurement and rms calculations. A fixed
function digital signal processor (DSP) executes this signal
processing.
The ADE7978 measures the active, reactive, and apparent energy
in various 3-phase configurations, such as wye or delta services,
with both three and four wires. The ADE7978 provides system
calibration features for each phase, gain calibration, and optional
offset correction. Phase compensation is also available, but it is
not necessary because the currents are sensed using shunts. The
CF1, CF2, and CF3 logic outputs provide a wide selection of
power information: total active, reactive, and apparent powers;
the sum of the current rms values; and fundamental active and
reactive powers.
The ADE7978 incorporates power quality measurements, such
as short duration low or high voltage detection, short duration
high current variations, line voltage period measurement, and
angles between phase voltages and currents. Two serial interfaces,
SPI and I2C, can be used to communicate with the ADE7978.
A dedicated high speed interface—the high speed data capture
(HSDC) port—can be used in conjunction with I2C to provide
access to the ADC outputs and real-time power information.
The ADE7978 also has two interrupt request pins, IRQ0 and
IRQ1, to indicate that an enabled interrupt event has occurred.
The ADE7978 is available in a 28-lead, Pb-free LFCSP package.
Applications
- Shunt-based polyphase meters
- Power quality monitoring
- Solar inverters
- Process monitoring
- Protective devices
- Isolated sensor interfaces
- Industrial PLCs
