3656JG

Overview

The Texas Instruments 3656JG is a transformer-coupled isolation amplifier providing complete signal and power isolation in integrated circuit form. It features three-port isolation with independent grounds for input, output, and isolated power. The device utilizes a patented modulation technique and miniature hybrid transformer to achieve an 8000V isolation test voltage and 125dB common-mode rejection at 60Hz. Electrical specifications include a 30kHz small-signal bandwidth, 1% initial gain accuracy, and a maximum leakage current of 0.5μA at 120V, 60Hz. It operates within a temperature range of 0°C to +70°C.

Feature Summary

• Provides total galvanic isolation for both signal transmission and power delivery using internal transformer coupling.
• Supports three completely independent ground systems to eliminate ground loops and off-ground measurement errors.
• Features uncommitted operational amplifiers at the input and output stages for versatile closed-loop configuration.

Applications

• Medical patient monitoring and diagnostic instrumentation
• Industrial ground loop elimination and off-ground signal measurement
• Nuclear input/output and power isolation

Procurement Notes

Verify component authenticity through authorized distributors or direct manufacturer channels. Confirm that the specific JG suffix matches the required 0°C to +70°C operating temperature range. Ensure compliance with relevant safety standards for medical or industrial environments. Review datasheet notes regarding isolation rating degradation under prolonged high-temperature exposure.

Selection Notes

Select this component when simultaneous signal and power isolation is required without external transformers. The JG variant is appropriate for applications requiring operation up to +70°C. Consider the internal isolated power capability if external supplies are unavailable. Verify that the 30kHz bandwidth meets the system's frequency response requirements.

Part Context

The 3656 series represents a pioneering analog signal processing advancement by Burr-Brown Corporation, now part of Texas Instruments. It was the first amplifier to integrate total isolation functions into a single IC package. The 3656JG belongs to this family, distinguished by its specific temperature rating and gain accuracy parameters compared to other variants like the AG or BG.

Replacement Considerations

Direct replacements must match the 20-Lead ISO Omni (102A) ceramic DIP package and provide equivalent transformer-coupled isolation. Verify that substitute components offer comparable 8000V isolation test ratings and similar three-port isolation capabilities.

FAQ

How does the 3656JG achieve isolation between the input and output?

Isolation is achieved using a patented modulation technique and a miniature hybrid transformer. A pulse generator modulates the input signal onto a carrier wave, which is coupled across the transformer windings to demodulators on the isolated side.

What is the maximum continuous isolation voltage rating?

The rated continuous isolation voltage is 3500 VDC between the input common and output common, and 3500 VDC between the input common and the isolated power negative terminal.