Texas Instruments INA139NA/3KG4

Overview

INA139NA/3KG4 from Texas Instruments is a high-side, unipolar current shunt monitor IC in 5-pin SOT-23 package, delivering 1000 µA/V transconductance, ±1.5 mV input offset voltage (max), and operation across –40°C to +125°C. It enables precision current sensing in automotive power rails, battery chargers, and industrial power management where input common-mode voltage reaches up to 40 V while supply voltage remains as low as 2.7 V.

For engineers reviewing the INA139NA/3KG4 datasheet, INA139NA/3KG4 pinout, INA139NA/3KG4 application, or INA139NA/3KG4 equivalent, key selection criteria include its 40 V common-mode range, 60 µA quiescent current, current-output architecture requiring external RL for gain setting, and compatibility with high-side shunt configurations where VIN+ exceeds V+.

Technical Context

The INA139NA/3KG4 integrates a high-voltage precision op amp, laser-trimmed thin-film resistors, and a low-noise output transistor to achieve accurate differential-to-current conversion. Its input stage operates with independent common-mode and supply voltage domains - VIN+ supports 2.7 V to 40 V while V+ ranges from 2.7 V to 40 V - enabling true high-side sensing without level-shifting circuitry.

It delivers fixed transconductance of 1000 µA/V (±1% typical) over temperature, with bandwidths of 440 kHz (RL = 10 kΩ) and 220 kHz (RL = 20 kΩ). Output compliance is governed by both V+ and VIN+, limiting maximum VO to min[(V+) − 1.2 V, VIN+ − 0.6 V], ensuring stable operation under varying rail conditions.

Key Specifications

Pinout & Package

INA139NA/3KG4 uses a 5-pin SOT-23 (DBV) package measuring 2.90 mm × 1.60 mm, optimized for space-constrained PCB layouts in power modules and portable electronics.

Key Features

Applications

Equivalent & Alternatives

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

Compared with INA139NA/3KG4, INA169NA/3K extends voltage headroom but sacrifices high-temperature capability, while MAX4080TASA+ trades configurability for integration - making INA139NA/3KG4 optimal for cost-sensitive, thermally demanding, and gain-flexible high-side monitoring.

Availability

INA139NA/3KG4 is available at Aetrix Electronics and suitable for automotive battery monitoring, industrial power supply overcurrent protection, and portable device charger management requiring stable component supply across extended temperature and voltage ranges.

Supply support for INA139NA/3KG4 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 company designing analog ICs, embedded processors, and digital signal solutions for industrial, automotive, and communications markets.

The INA139 product line delivers high-side current sensing with minimal external components, targeting applications where space, power, and accuracy constrain traditional op-amp-based solutions.

FAQ

What is the maximum common-mode voltage supported by the INA139NA/3KG4?

The INA139NA/3KG4 supports a maximum input common-mode voltage of 40 V. This rating applies to the VIN+ pin and is independent of the V+ supply voltage, which itself operates from 2.7 V to 40 V. The device maintains specified performance across this full range, enabling reliable high-side current sensing in 24 V and 36 V industrial and automotive systems without external level-shifting circuitry. Exceeding 40 V on VIN+ risks violating absolute maximum ratings.

Can the INA139NA/3KG4 measure bidirectional current?

The INA139NA/3KG4 is designed for unipolar (single-direction) current measurement only: it requires VIN+ > VIN– and outputs zero current if polarity reverses. To measure bidirectional current, two INA139NA/3KG4 devices must be used - one across the shunt with forward orientation, another with reversed inputs - combined with a comparator or differential ADC to interpret direction. TI's application note SBOS181F details this dual-INA configuration in Figure 15 and Figure 17.

What is the role of the external load resistor RL in the INA139NA/3KG4 circuit?

The external load resistor RL converts the INA139NA/3KG4's output current (IO = 1000 µA/V × VSENSE) into a measurable voltage (VO = IO × RL). RL directly sets system gain - e.g., RL = 10 kΩ yields 10 V/V - and must be connected between OUT (pin 1) and GND (pin 2). RL values up to 100 kΩ maintain accuracy due to the device's high output impedance; however, bandwidth decreases inversely with RL (e.g., 440 kHz at 10 kΩ, 220 kHz at 20 kΩ).

Does the INA139NA/3KG4 require a separate ground connection for the shunt resistor?

Yes - the INA139NA/3KG4 requires a dedicated low-impedance analog ground connection at pin 2 (GND), which serves as the reference for internal biasing and output current sinking. The shunt resistor's low-side terminal connects to VIN– (pin 4), not GND. This separation prevents ground-loop errors and preserves accuracy when the shunt is placed in a high-current return path shared with digital or power grounds. TI recommends star-grounding GND near the shunt location.

How does temperature affect the accuracy of the INA139NA/3KG4?

Temperature impacts INA139NA/3KG4 accuracy primarily through offset voltage drift (1 µV/°C max) and transconductance stability (±1% typical over –40°C to +125°C). Total output error remains within ±2% across temperature and supply variations, as confirmed in Figure 4 and Figure 5 of SBOS181F. The device's guaranteed operation to +125°C makes it suitable for under-hood automotive use, where offset drift contributes less than ±0.1% error over a 100°C span at typical sense voltages.