Texas Instruments ISO120G

Overview

ISO120G from Burr-Brown Corporation is a precision isolation amplifier using duty-cycle modulation across a 2pF differential capacitive barrier, delivering ±0.01% max nonlinearity, 115dB IMR at 60Hz, and 1500Vrms continuous isolation rating. It operates over –25°C to +85°C with ±4.5V to ±18V dual supplies and supports both free-running (60kHz bandwidth) and externally synchronized modes for noise rejection in industrial signal conditioning.

For engineers reviewing the ISO120G datasheet, ISO120G pinout, ISO120G application, or ISO120G equivalent, this page provides verified technical context, real-world design meaning of key specs, hermetic DIP-24 package details, functional alternatives with documented differences, and supply support for long-lifecycle industrial deployments requiring galvanic signal isolation.

Technical Context

The ISO120G implements a laser-trimmed, two-section architecture: an input integrator (A1) converts VIN into a duty-modulated triangular waveform referenced to Signal Com 1, transmitted digitally across matched 1pF barrier capacitors. The output section (A2) demodulates the signal using a synchronized switched-current source and sample-and-hold circuitry to reconstruct VOUT = VIN with ripple suppression.

It supports user-controlled carrier frequency via external C1/C2 capacitors or direct Ext Osc synchronization (400kHz–700kHz square wave or ±4V sine), enabling precise nulling of system clock harmonics and ground-loop interference. Its 2pF barrier impedance (10¹⁴ Ω || 2 pF) ensures signal integrity independent of barrier aging or humidity, unlike transformer- or opto-based isolators.

Key Specifications

Pinout & Package

ISO120G uses a 0.3"-wide 24-pin hermetic Dual In-line Package (DIP), pin-compatible with ISO120BG and ISO120SG variants. The package features ceramic-to-metal seals and gold-plated leads for high-reliability operation from –25°C to +85°C.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar isolation amplifier applications.

Compared with ISO120G, AMC1301DWVR offers higher isolation and digital output but sacrifices analog flexibility and external tuning; ISO122JP provides smaller footprint and simpler layout but lacks synchronization, hermetic reliability, and the ultra-low nonlinearity needed for precision transducer interfaces.

Availability

ISO120G is available at Aetrix Electronics and suitable for industrial process control, power monitoring, and biomedical instrumentation requiring stable component supply across extended product lifecycles.

Supply support for ISO120G includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.

Manufacturer

Burr-Brown Corporation was a U.S.-based analog semiconductor pioneer (acquired by Texas Instruments in 2000), renowned for high-precision linear ICs including instrumentation amplifiers, data converters, and isolation products.

The ISO120G belongs to Burr-Brown's precision isolation amplifier family, designed specifically for high-fidelity analog signal transmission across galvanic barriers in noisy industrial and medical environments where long-term stability and certified isolation integrity are mandatory.

FAQ

What is the maximum continuous isolation voltage rating for ISO120G?

The ISO120G is rated for 1500Vrms continuous isolation voltage at 60Hz across its capacitive barrier. This rating is validated by 100% production partial discharge testing at 2500Vrms for 1 second with ≤5pC discharge, ensuring long-term reliability in high-voltage industrial monitoring applications where the ISO120G interfaces with mains-referenced sensors.

Can ISO120G operate with asymmetric supply voltages such as +15V/–5V?

No, the ISO120G requires symmetrical dual supplies (e.g., ±4.5V to ±18V) on both VS1 and VS2 rails. Asymmetric operation violates the internal charge-balancing architecture of the modulator/demodulator stages and causes severe gain error and increased nonlinearity. The ISO120G datasheet explicitly specifies "VS1 = VS2" in all test conditions, and the internal 100µA current sources depend on matched rail magnitudes for duty-cycle fidelity.

How does the ISO120G achieve 115dB isolation mode rejection at 60Hz?

The ISO120G achieves 115dB IMR at 60Hz through its differential 2pF capacitive barrier combined with high-common-mode-rejection sense amplifiers on both sides of the barrier. The barrier's inherent symmetry and the laser-trimmed matching of input/output integrator components ensure that 60Hz ground noise couples equally onto both C1H/C1L and C2H/C2L nodes, canceling at the demodulator output. This is confirmed in the ISO120G datasheet's IMR vs Frequency plot, where 115dB is measured under 1500Vrms test conditions.

What external components are required for basic operation of ISO120G?

No external components are required for basic 60kHz-bandwidth operation of the ISO120G. Only local 1µF tantalum bypass capacitors on each supply pin (+VS1, –VS1, +VS2, –VS2) are mandatory per the datasheet. C1 and C2 capacitors are optional and used only when reducing bandwidth to 6kHz for improved nonlinearity (±0.01%) or enabling external synchronization via the Ext Osc pin.

Is ISO120G pin-compatible with ISO121G?

No, ISO120G is not pin-compatible with ISO121G. The ISO120G uses a 24-pin DIP package (drawing number 225), while the ISO121G uses a 40-pin DIP (drawing number 206). Pin numbering differs completely: ISO120G pin 1 is Signal Com 1, whereas ISO121G pin 1 is Gnd 1. The connection diagram explicitly states "First pin number is for ISO120. Second pin number is for ISO121," confirming incompatible pinouts and package footprints.