Texas Instruments ISO122PG4

Overview

ISO122PG4 from Texas Instruments is a precision analog isolation amplifier with galvanic isolation via integrated 2-pF differential capacitive barrier, fixed unity gain (1 V/V), ±10 V output swing, 50-kHz small-signal bandwidth, and 140 dB isolation mode rejection at 60 Hz - used in industrial transducer signal conditioning where ground-loop elimination and high-voltage integrity are critical.

For engineers reviewing the ISO122PG4 datasheet, ISO122PG4 pinout, ISO122PG4 application, or ISO122PG4 equivalent, this page delivers verified specifications, validated pin functions, real-world use cases for thermocouple/RTD isolation and 4–20 mA loop interfaces, and confirmed alternative options for precision isolated analog signal transmission.

Technical Context

The ISO122PG4 employs duty-cycle modulation-demodulation across an embedded capacitive barrier, transmitting input signals digitally to eliminate barrier-dependent drift and distortion. Its modulator integrates VIN/200 kΩ against a switched ±100-µA current source, generating a 500-kHz carrier-modulated waveform.

The demodulator reconstructs the analog output using a sense amplifier, integrator A2, and sample-and-hold stages that suppress inherent 500-kHz ripple (20 mV_p-p). Input and output sections are laser-trimmed for matching, enabling 0.020% max nonlinearity and 200 µV/°C V_OS drift over –25°C to +85°C.

Key Specifications

Pinout & Package

ISO122PG4 is supplied in a 16-pin plastic DIP (PDIP-NVF) package measuring 17.90 mm × 7.50 mm, with creepage and clearance optimized for reinforced isolation. Pin 1 is +VS1; pin 16 is GND (high-side reference); pin 8 is GND (low-side reference); pin 7 is VOUT; pin 15 is VIN.

Key Features

Applications

Equivalent & Alternatives

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

Compared with ISO122PG4, ISO124P trades precision for cost and AMC1301DWVR replaces analog output with digital modulation - making ISO122PG4 uniquely suited for drop-in replacement in legacy analog signal chains requiring guaranteed 0.020% linearity and 140 dB IMR without firmware changes.

Availability

ISO122PG4 is available at Aetrix Electronics and suitable for industrial process control, motor SCR feedback, and PC-based data acquisition requiring stable component supply, long-lifecycle support, and traceable sourcing for safety-critical designs.

Supply support for ISO122PG4 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

Texas Instruments is a global semiconductor leader specializing in analog and embedded processing technologies, with decades of expertise in precision signal conditioning and isolation solutions.

The ISO122 product line was engineered specifically for high-reliability industrial analog isolation - delivering tested 1500 V_rms barrier integrity, low-drift performance, and ease-of-use in transducer interface and ground-loop elimination applications.

FAQ

What is the maximum input voltage the ISO122PG4 can handle without damage?

The ISO122PG4 has an absolute maximum VIN rating of ±100 V, independent of supply voltage. However, its specified linear input range is ±10 V (±12.5 V max). Operation beyond ±10 V introduces nonlinearity but remains within safe operating limits as long as supply voltages are ≥±15 V and internal power dissipation stays within thermal limits. The ISO122PG4's input structure is current-based (I = V_IN/200 kΩ), which inherently provides overvoltage tolerance.

Does the ISO122PG4 require external components for basic operation?

No - the ISO122PG4 operates with zero external components for core functionality. It features fixed unity gain and internally trimmed circuitry. Only mandatory external elements are 1-µF tantalum bypass capacitors on each supply pin (+VS1, –VS1, +VS2, –VS2), placed as close as possible to the device. Optional components include output low-pass filters (e.g., Sallen-Key) to suppress 500-kHz ripple when sub-millivolt accuracy is required.

Can the ISO122PG4 be used with single-supply operation on the high side?

Yes - the ISO122PG4 supports single-supply-derived bipolar operation on the high side. A common method uses a 5.1-V Zener diode referenced to +VS1 to generate –VS1, enabling ±15 V operation from a +30 V source. The ISO122PG4's input current architecture allows VIN to exceed the high-side supply rails, making it compatible with unregulated or Zener-biased supplies. Full ±10 V output swing is maintained when VS2 is ±15 V.

What is the significance of the 140 dB IMR specification for the ISO122PG4?

The 140 dB isolation mode rejection (IMR) at 60 Hz quantifies the ISO122PG4's ability to reject common-mode voltage noise coupled across the isolation barrier - such as AC mains interference in factory environments. At 140 dB, a 1-V 60 Hz noise signal on the barrier induces only 10 µV of error at VOUT. This enables stable, drift-free measurements in electrically noisy settings like motor control cabinets or PLC backplanes where ground potentials differ by hundreds of volts.

How does the ISO122PG4 handle input signals above 250 kHz?

The ISO122PG4's 500-kHz carrier frequency imposes a Nyquist limit of 250 kHz. Input signals above this frequency undergo aliasing: their energy folds down into the baseband, producing spurious outputs below 250 kHz. For example, a 800-kHz 1000-V_rms IMV generates a 32-mV error at 200 kHz plus a 1-V 800-kHz component at VOUT. Therefore, the ISO122PG4 is specified for linear operation only up to 250 kHz; anti-aliasing filtering is required for higher-frequency inputs.