sponsoredMODULATOR High current sensing with new ACPL-736J ±50mV External Clock Sigma Delta Modulator

The ACPL-736J is a high precision, optically isolated sigma delta modulator certified to reinforced isolation up to a maximum transient overvoltage of 8000Vpk, maximum working insulation voltage of 1414Vpk per IEC/EN 60747-5-5 and 5000Vrms isolation voltage per UL1577 certification. The optical isolation barrier is immune to electromagnetic interference and capable to withstand common mode transients for reliable and accurate shunt based current measurements in industrial applications.

Higher current sensing may lead to higher power dissipation in the shunt resistor which is not desirable for system designers. This can be resolved by using a smaller input range isolated modulator e.g +/-50mV. Table 1 shows that for the same current measured, the shunt losses can be 75% smaller. Table 2 shows that for the same shunt power loss budget, the measured current range can be 4 times higher.

The ACPL-736J is a high performance high precision robust sigma delta modulator based on Broadcom optical isolation technology. The isolation barrier, which is highly resistant to electrical and magnetic interference, helps to prevent electrical shock to human operator and damage to low voltage circuit components such as expensive ASICs or FPGAs by separating the high voltage and low voltage circuits within the system. The ACPL-736J has a ±50mV linear input range and full scale of ±80mV. The small input range of ±50 mV enables higher current measurements with significant reduction in shunt heat dissipation and is therefore ideal for shunt-based current sensing in high voltage applications where isolation is required e.g. motor phase current measurement.

The ACPL-736J is a 1-bit, second-order sigma delta modulator that continuously oversample the differential analog input using the external provided clock and convert the input into a high speed, single bit data stream. The output data, which consists of a stream of digital ones and zeros, is synchronous to the external clock with a frequency range from 5MHz to 21MHz. By using an appropriate digital filter (such as sinc3 filter) to decimate the bitstream, the device is capable to achieve 16 bits resolution (12 bits ENOB) with a SNR of 81dB at 78kHz output data rate with a 20MHz external clock frequency.

The ACPL-736J operates from a nominal 5V power supply and the CMOS output interface for both clock input and data output operate from a 3V to 5.5V power supply. The ACPL-736J offers excellent DC performance supporting high precision current sensing such as maximum offset drift of -2µV/°C to 1μV/°C and maximum gain error of ± 1%. The ACPL-736J also offers superior AC performance such as typical SNR of 81dB and SNDR of 80dB over the specified operating temperature and linear input range. The common-mode transient immunity is 80kV/µs that effectively enable the device to withstand common mode transients and continue to operate normally in the event when transients occur.

The ACPL-736J is available in a SO-16 package and specified over the operating temperature range from - 40°C to 110°C, which covers all industrial application temperature range. The ACPL-736J has passed all safety and regulatory approval and is certified to IEC/EN 60747-5-5: V_IORM =1414 Vpeak maximum working insulation voltage, UL1577 V_ISO = 5000V_RMS /1min isolation withstand voltage with double protection and CAN/CSA-C22.2 No. 62368-1.

Visit us at PCIM Hall 9-526 to find out more!

(ID:50344336)