Texas Instruments 2A997

Overview

INA117 from Texas Instruments is a precision unity-gain difference amplifier optimized for high common-mode voltage measurement in industrial power systems. It delivers ±200V continuous common-mode input range, 0.001% nonlinearity, and 86dB minimum CMRR at DC - enabling accurate differential sensing across battery strings, motor drives, and grounded breaker monitoring circuits.

For engineers reviewing the INA117 datasheet, INA117 pinout, INA117 application, or INA117 equivalent, this page provides verified technical context, validated pin functions, real-world application constraints (e.g., RC compensation for sense resistors >20Ω), and two confirmed alternative parts with documented functional trade-offs.

Technical Context

The INA117 integrates a precision op amp with a laser-trimmed thin-film resistor network to achieve 0.02% max gain error and 200kHz bandwidth. Its internal architecture rejects common-mode signals up to ±200V while preserving microvolt-level differential accuracy - critical for current sensing without galvanic isolation.

Input protection circuitry withstands ±500V momentary common-mode and differential overloads. The compensation pin (Pin 8) must be grounded or AC-coupled to V+ via 0.1µF to cancel substrate capacitance effects and maintain specified dynamic performance.

Key Specifications

Pinout & Package

INA117 is available in SO-8 (D package), PDIP-8 (P package), and TO-99 metal can (LMC package). This description applies to all variants including INA117KU, INA117P, and INA117AM.

Key Features

Applications

Equivalent & Alternatives

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

Compared with AD629ARZ and INA282AIDR, the INA117 uniquely combines ±200V common-mode tolerance, laser-trimmed unity gain, and dual reference inputs - making it irreplaceable in battery stack monitoring and grounded-breaker detection where both voltage range and configurability are essential.

Availability

INA117 is available at Aetrix Electronics and suitable for battery management systems, industrial motor drives, ground-fault detection circuits, and high-noise factory automation requiring stable component supply across extended temperature ranges.

Supply support for INA117 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 amplifiers and industrial signal conditioning.

The INA117 belongs to TI's high-voltage difference amplifier product line, engineered specifically for replacing isolation amplifiers in cost-sensitive industrial power monitoring applications where galvanic isolation is not mandated by safety standards.

FAQ

What is the maximum continuous common-mode voltage the INA117 can handle?

The INA117 supports ±200V continuous common-mode input voltage when powered with ±15V supplies. This rating is explicitly specified in the Absolute Maximum Ratings table and confirmed in Typical Performance Curves showing operation up to ±200V across the full temperature range. Exceeding this value risks permanent damage, even if transient protection ratings allow ±500V for short durations. Always verify supply rails and input clamping in your layout before deploying INA117 in high-voltage systems.

Does the INA117 require external trimming for offset or CMRR in standard unity-gain configuration?

No, the INA117 does not require external trimming in basic unity-gain use (VO = V3 – V2). Its laser-trimmed thin-film resistor network guarantees 0.02% gain error and 86dB CMRR without adjustment. Figures 2 and 3 in the datasheet show optional trim circuits only for applications demanding sub-10µV offset or >90dB CMRR - which exceed the standard specification. For most current sensing and battery monitoring tasks, the INA117 performs to datasheet limits out-of-the-box.

Can the INA117 drive heavy capacitive loads such as long cables or ADC input capacitors?

The INA117 is stable driving up to 1000pF capacitive load, as verified in the SPECIFICATIONS table under "Capacitive Load". Driving larger loads (e.g., >2nF cables) will cause peaking or oscillation. For such cases, TI recommends adding a small series resistor (e.g., 20Ω) between the INA117 output and the cable, or using the buffered configuration shown in Figure 7 with an OPA1013. Never directly connect the INA117 output to unbuffered SAR ADC inputs exceeding 1000pF without verifying stability in simulation or hardware.

How does sense resistor value affect INA117 performance in current measurement circuits?

Sense resistor value directly impacts both CMRR and gain accuracy. Resistors above 20Ω degrade CMRR unless compensated with RC = RS (Figures 4–6); resistors above ~100Ω introduce >0.02% gain error due to input loading. The corrected value RS' = RS × (1 + RS/380kΩ) compensates for this. For example, a 1kΩ shunt requires RS' = 1002.6Ω. These effects are quantified in the APPLICATION INFORMATION section and must be applied during design - they are not mitigated by layout alone.

Is the INA117 suitable for measuring leakage currents below 1µA?

Yes, the INA117 can measure sub-µA leakage currents when paired with a high-input-impedance buffer like the OPA111, as demonstrated in Figure 8. In that configuration, the INA117 operates with ±200V common-mode range while the buffer handles ultra-low current sourcing. However, the INA117 alone is not appropriate for direct picoampere measurements due to its 800kΩ differential input impedance and input bias current limitations. Always use the buffered topology and isolated power for leakage testing - never rely on the INA117's native inputs for currents below 100nA.