ACPL-C877 Precision Optically Isolated Digital Voltage Sensor

Broadcom ACPL-C877 1-bit, second-order sigma-delta modulators convert an analog input signal into a high-speed data stream by integrating galvanic isolation based on optical coupling technology. The wide 2 V input voltage range and the high input impedance of 1 GΩ make the device well-suited for direct connection to the resistive dividers in high-voltage applications, including motor drives and renewable energy systems. The ACPL-C877 has a dynamic range of 76 dB with an appropriate digital filter and operates from a 5 V power supply.

The sigma-delta modulator continuously measures the analog input by over-sampling using an internally built precision clock. The signal information is contained in the modulator data as a density of ones with a data rate of 10 MHz. The data is then encoded and transmitted across the isolation boundary, where the clock and data are recovered and decoded into a high-speed data stream of digital ones and zeros. The original signal information can be reconstructed with a digital filter. The serial interface for data and clock has a wide supply range of 3 V to 5.5 V. Combined with superior optical coupling technology, the modulator delivers high noise margins and excellent immunity against isolation-mode transients. With a 0.5 mm minimum distance through insulation (DTI), the ACPL C877 provides reliable reinforced insulation and high working insulation voltage, suitable for fail-safe designs. This isolation performance is superior to alternatives, including devices based on capacitive or magnetic coupling with DTI in the micrometer range. Offered in an SSO8 package, the isolated ADC delivers the reliability, small size, superior isolation, and overtemperature performance motor drive designers need to accurately measure voltage.