ADE7933:  3-Channel, Isolated, Sigma Delta ADC

The ADE7978 and ADE7933/ADE7932 form a chipset dedicated to measuring 3-phase electrical energy measurement using shunts as current sensors.

The ADE7933/ADE7932 are isolated three-input channel, analog to digital converter (ADC) for polyphase energy metering applications using shunt current sensors. They feature three 24-bit analog to digital converters, each of which provides 70dB signal to noise ratio over a 3 kHz signal bandwidth. One channel is dedicated to measuring the voltage across a shunt when the shunt is used for current sensing. Two additional channels are dedicated to measuring voltages, which are usually sensed using resistor dividers. The ADE7933 and ADE7932 also measure the temperature of the IC. The ADE7932 is the same as the ADE7933 but it does not include the second voltage measurement.

The ADE7933/ADE7932 integrate an isolated dc-to-dc converter. Based on the Analog Devices, Inc., isoPower® technology, the dc-to-dc converter provides the regulated power required by the first stage of the ADCs. This device eliminates 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 ADE7933/ADE7932 contains a digital interface, specially designed to provide the ADE7978 access to its ADC outputs and other configuration settings.

The ADE7933/ADE7932 is available in the 20-lead wide body SOIC, Pb-free package with increased creepage.

The ADE7978 is a high accuracy, 3-phase electrical energy measurement IC with serial interfaces and three flexible pulse outputs. The ADE7978 may interface with up to four ADE7933/ADE7932s. It 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, although available, is not necessary because the currents are sensed using shunts. The CF1, CF2, and CF3 logic outputs provide a wide choice of power information: total active, reactive, and apparent powers, or 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 detections, 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 the 28-lead LFCSP, Pb-free package.

APPLICATIONS

• Energy metering systems
• Power monitoring