Texas Instruments INA138NA/250G4

Overview

INA138NA/250G4 from Texas Instruments is a unipolar high-side current shunt monitor IC designed for precision measurement of load current via a sense resistor. It features 200 µA/V transconductance, 2.7 V to 36 V supply range, ±1 mV max offset voltage at +25°C, and operates across –40°C to +125°C in SOT-23-5 package - used in battery chargers, power management systems, and telecom equipment.

For engineers reviewing the INA138NA/250G4 datasheet, INA138NA/250G4 pinout, INA138NA/250G4 application, or INA138NA/250G4 equivalent, key selection considerations include its independent common-mode and supply voltage ranges (up to 36 V), low 25 µA quiescent current, current-output architecture requiring external RL for gain setting, and suitability for high-side sensing where VIN+ may exceed V+.

Technical Context

The INA138NA/250G4 integrates a precision op amp, laser-trimmed thin-film resistors, and a low-noise output transistor to deliver accurate current-to-current conversion. Its input stage supports common-mode voltages up to 36 V while operating from as low as 2.7 V supply - enabling direct connection on either side of the shunt without compromising accuracy.

It functions as a transconductance amplifier with fixed gm = 200 µA/V (±2% over temperature), converting differential input voltage (VIN+ – VIN–) into proportional output current. Gain is set externally via RL, allowing scalable voltage output (e.g., 1 V/A with RL = 5 kΩ), while maintaining high output impedance (>1 GΩ) and minimal loading effects.

Key Specifications

Pinout & Package

INA138NA/250G4 is housed in a 5-pin SOT-23 package (2.90 mm × 1.60 mm body size) with exposed pad for thermal performance. Pin numbering follows JEDEC standard top-view orientation.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar high-side current monitoring applications.

Compared with INA168NA/250G4, the INA138NA/250G4 trades 24 V common-mode headroom for identical performance below 36 V, while MAX4080TASA+ provides higher bandwidth and integrated gain but requires different footprint and layout - making INA138NA/250G4 optimal for cost-sensitive, space-constrained 24–36 V high-side monitoring.

Availability

INA138NA/250G4 is available at Aetrix Electronics and suitable for battery chargers, industrial power supplies, telecom line cards, and portable medical devices requiring stable component supply and long-term manufacturability.

Supply support for INA138NA/250G4 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, embedded processing, and connectivity technologies, with decades of expertise in precision signal conditioning and power management ICs.

The INA1x8 product line was engineered specifically for high-accuracy, low-power, high-side current sensing in space-constrained applications - targeting battery-powered, telecom, and industrial systems where supply and common-mode independence is critical.

FAQ

What is the maximum common-mode voltage supported by the INA138NA/250G4?

The INA138NA/250G4 supports an input common-mode voltage range of 2.7 V to 36 V. This means VIN+ and VIN– can each sit anywhere within that range relative to ground, enabling reliable high-side sensing on 24 V and 36 V rails. Exceeding 36 V risks permanent damage, as confirmed in Absolute Maximum Ratings - use INA168NA/250G4 for 48 V or 60 V applications.

How is gain configured for the INA138NA/250G4?

Gain for the INA138NA/250G4 is set externally using a single load resistor (RL) connected between the OUT pin and ground. With a transconductance of 200 µA/V, the voltage gain equals RL × 200 µA/V (e.g., RL = 10 kΩ yields 2 V/V). The device itself has no internal gain-setting resistors - all scaling is determined by RL's value and tolerance.

Can the INA138NA/250G4 measure bidirectional current?

The INA138NA/250G4 is specified for unipolar operation only: it requires VIN+ ≥ VIN– and delivers zero output current if polarity reverses. To measure bidirectional current, two INA138NA/250G4 devices must be used - one across the shunt in each direction - with external logic (e.g., comparator) selecting the active output, as shown in TI's Figure 15 application circuit.

What is the recommended decoupling for the V+ pin of the INA138NA/250G4?

A 0.1 µF ceramic capacitor placed as close as possible to the V+ pin (Pin 5) and GND (Pin 2) is mandatory for stable operation. TI's layout guidelines specify this capacitor must have low ESL and be routed with short, wide traces. For noisy environments, adding a parallel 10 µF tantalum or aluminum polymer capacitor improves low-frequency PSRR without affecting bandwidth.

Does the INA138NA/250G4 require a separate ground connection for the load shunt?

No - the INA138NA/250G4 does not require the shunt's low-side node to connect to the IC's GND (Pin 2). Its inputs are fully differential and isolated from GND, allowing the shunt to float anywhere within the 2.7 V to 36 V common-mode window. GND (Pin 2) serves only as the internal reference for the output stage and bias circuitry.