Broadcom's 20mhz internal clock modulator converts analog signals into high-speed data streams

     Broadcom AcPL-C740 is a 1-bit, second-order sigma-delta modulator that converts analog input signals into high-speed data streams through current isolation based on optical coupling technology. The ACPL-C740 operates on a 5v power supply with a dynamic range of 86 dB and appropriate digital filters. The ±200 mV(±320 mV at full scale) differential input is ideal for applications that connect directly to shunt resistors or other low-level signal sources, such as motor phase current measurements.

     Analog inputs are continuously sampled using the sigma-delta oversampling method of the onboard clock. The signal information is contained in the modulator data, with a data density of 1 and a data rate of 20 MHZ, and the data is encoded and transmitted across the isolation boundary, where they are recovered and decoded into high speed digital 1 and 0 data streams. The original signal information can be reconstructed by digital filter. The serial interface for data and clock has a wide power supply range of 3v to 5.5V.

     Combined with superior optical coupling technology, the modulator provides high noise margin and excellent immunity against isolated mode transients. With a minimum through-insulation distance (DTI) of 0.5 mm, the ACPL-C740 provides reliable enhanced insulation and high working insulation voltage for a fail-safe design.

     This excellent isolation performance is superior to other options, including capacitance-based or magnetically coupled devices with DTI in the micron range. In a stretched SO-8 (SSO-8) package, isolated ADCs offer reliability, small size, superior isolation and overtemperature performance, requiring motor drive designers to accurately measure current at a much lower price than traditional current sensors.