3656KG

Overview

The Texas Instruments 3656KG 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 power. The device includes an internal pulse generator operating at approximately 750kHz to drive a miniature hybrid transformer. Key electrical specifications include a rated continuous isolation voltage of 3500 VDC, a test voltage of 8000 VDC, and a maximum leakage current of 0.5 μA at 120V, 60Hz. It offers a small-signal bandwidth of 30 kHz and supports gains up to 1000 V/V.

Feature Summary

• Provides total galvanic isolation for both signal transmission and power delivery using a patented modulation technique and miniature hybrid transformer.
• Supports three completely independent isolated grounds, allowing flexible system grounding configurations without common reference points.
• Generates internal isolated power available to supply external circuitry at either the input or output stages.
• Features uncommitted operational amplifiers at both input and output stages to allow versatile closed-loop gain configurations.

Applications

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

Procurement Notes

Verify the specific suffix KG against the manufacturer's datasheet to confirm temperature range and accuracy class. Confirm package type matches the required 20-lead ISO Omni ceramic DIP. Check for lead-free compliance status as older Burr-Brown/TI parts may not be RoHS compliant. Ensure design-in documentation references the correct pinout for the 3656 series.

Selection Notes

Select this component when high-voltage isolation between signal and power domains is required. The 3656KG is suitable for applications needing three-port isolation where input, output, and power grounds must remain independent. Consider the internal power generation capability if external isolated supplies are unavailable. Verify that the 30 kHz bandwidth meets the signal frequency requirements.

Part Context

The 3656 series was developed by Burr-Brown Corporation, which was later acquired by Texas Instruments. This device represents an early advancement in analog signal processing by integrating isolation functions into a single IC. The 3656KG variant specifically denotes the commercial temperature range and accuracy class within the broader family of transformer-coupled isolation amplifiers.

Replacement Considerations

Direct replacements should be sought from the Burr-Brown 3656 series (e.g., 3656AG, 3656BG) ensuring pin compatibility. Modern alternatives like the AMC1100 offer digital isolation but require different interface considerations. Verify that any substitute maintains the three-port isolation requirement and similar gain configuration flexibility.