3-Phase Metrology IC for Polyphase Shunt Meters
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.
- Shunt-based polyphase meters
- Power quality monitoring
- Solar inverters
- Process monitoring
- Protective devices
- Isolated sensor interfaces
- Industrial PLCs
At least one model within this product family is in production and available for purchase. The product is appropriate for new designs but newer alternatives may exist.
The ADE7978/ADE7933 evaluation kit includes two boards that allow the performance of the ADE7978 and ADE7933 polyphase multifunction energy metering chipset to be evaluated in a context very close to an actual three phase meter implementation. The kit requires purchasing a third board, called EVAL-SDP-CB1Z, the controller board for the System Demonstration Platform. The ADE7978/ADE7933 evaluation kit includes evaluation software, written in LabVIEW®, that provides access to the registers and features of the ADE7978 using a PC interface.
The ADE7932 can also be evaluated with this board by using only two of the voltage channels; or if you prefer, you can order an ADE7932 sample and replace the corresponding ADE7933 chip on the board.
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