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Texas Instruments INA138NA/3KG4
- Part No.:
- INA138NA/3KG4
- Manufacturer:
- Texas Instruments
- Category:
- Current Regulation/Management
- Package:
- SC-74A, SOT-753
- Datasheet:
-
INA138NA/3KG4.pdf
- Description:
- IC CURRENT MONITOR 0.5% SOT23-5
- Quantity:
- Payment:
- Shipping:
Inventory:1,514
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Product details
Overview
INA138NA/3KG4 from Texas Instruments is a unipolar high-side current shunt monitor IC designed for precision measurement of load current via a sense resistor in power rails up to 36 V. It features 200 µA/V transconductance, ±1 mV max offset voltage at 25°C, 25 µA quiescent current, and operates from –40°C to +125°C in a 5-pin SOT-23 package. It is used in battery chargers and portable power management systems where low-error, high-common-mode sensing is required.
For engineers reviewing the INA138NA/3KG4 datasheet, INA138NA/3KG4 pinout, INA138NA/3KG4 application, or INA138NA/3KG4 equivalent, this page delivers verified technical context, real-world design meaning of key specs, validated pin functions, confirmed alternative parts with functional differences, and supply support details for industrial and embedded production use.
Technical Context
The INA138NA/3KG4 implements a precision current-output architecture: its internal op amp forces the shunt voltage across matched 5-kΩ gain-setting resistors, driving a bipolar output transistor whose collector current (IO) is proportional to input differential voltage (VIN+ – VIN–) with fixed transconductance (gm = 200 µA/V). Input common-mode voltage (2.7 V to 36 V) and supply voltage (V+) are independent, enabling true high-side placement above the load.
Its output is a current source requiring an external load resistor (RL) to convert to voltage - gain is set solely by RL, supporting scalable gains from 1× to >100×. Bandwidth varies inversely with RL: 800 kHz at 5 kΩ, dropping to 32 kHz at 125 kΩ, and total output error remains ≤±2.5% over temperature without calibration.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Transconductance | 200 µA/V - defines exact current output per mV of sensed shunt voltage; enables predictable, resistor-set gain without trimming. |
| Input Offset Voltage | ±1 mV max at 25°C - limits minimum detectable shunt voltage to ~5 mV for 1% error with 500-mV full-scale range. |
| Common-Mode Range | 2.7 V to 36 V - supports direct connection to 24-V industrial rails or 32-V telecom supplies without level-shifting. |
| Quiescent Current | 25 µA typical - allows permanent connection in battery-backed systems with negligible standby drain. |
| Operating Temperature | –40°C to +125°C - qualified for under-hood automotive modules and industrial motor drives. |
| Bandwidth | 32 kHz at 125 kΩ RL - sufficient for DC-DC converter current monitoring and slow transient detection. |
| Total Output Error | ±2.5% max over –40°C to +125°C - enables single-point calibration in cost-sensitive production test flows. |
Pinout & Package
INA138NA/3KG4 is housed in a 5-pin SOT-23 (DBV) package measuring 2.90 mm × 1.60 mm, optimized for space-constrained PCB layouts in portable and industrial equipment.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 - OUT | Current output terminal | Delivers precise output current IO = gm × (VIN+ – VIN–); requires external RL to ground for voltage conversion. |
| 2 - GND | Ground reference | Return path for internal circuitry; must be connected directly to system ground plane to minimize noise coupling. |
| 3 - VIN+ | Positive input | Connects to high-side of shunt resistor; must be more positive than VIN– for valid unipolar operation. |
| 4 - VIN– | Negative input | Connects to low-side of shunt resistor; differential input voltage must stay within –40 mV to +500 mV. |
| 5 - V+ | Power supply | Supplies internal amplifier and output transistor; independent of input common-mode voltage (2.7–36 V). |
Key Features
| Feature | Design Value |
|---|---|
| Single-resistor gain setting | RL alone determines system gain - eliminates need for matched resistor networks or calibration trim pots. |
| High common-mode rejection | 120 dB at DC - rejects ripple and noise on high-voltage rails, preserving accuracy in noisy switching environments. |
| Low quiescent current | 25 µA typical - enables always-on current monitoring in energy-harvesting and battery-critical applications. |
| Wide temperature performance | ±2.5% total output error over –40°C to +125°C - avoids thermal drift compensation in ruggedized designs. |
| Output compliance control | VOUTmax limited by (V+) – 0.7 V – VSENSE or VIN– – 0.5 V - prevents saturation when interfacing with ADCs or buffers. |
Applications
| Battery Charger Monitoring | Industrial Power Supply Feedback |
|---|---|
|
Use Scenario: Real-time charge/discharge current tracking in 12–24 V Li-ion battery packs with isolated MCU supervision. IC Role / Device Role / Timing Role: High-side current sensor converting shunt voltage to proportional output current for isolated analog front-end. Use Value: Enables accurate Coulomb counting and overcurrent protection without ground-loop interference or additional isolation components. |
Use Scenario: Load current feedback in programmable 24-V industrial DC power supplies with remote sensing. IC Role / Device Role / Timing Role: Precision current monitor feeding analog control loop of PWM controller or digital power manager. Use Value: Maintains regulation accuracy across wide line/load variations while surviving 36-V rail transients. |
| Portable Medical Device Power Management | Telecom Line Card Current Supervision |
|
Use Scenario: Low-power current monitoring in handheld ultrasound or infusion pumps powered by single-cell Li-ion. IC Role / Device Role / Timing Role: Ultra-low-IQ current sensor enabling continuous battery health logging during sleep mode. Use Value: Adds <1 µA/mA of measurement overhead, extending runtime without sacrificing safety-critical current visibility. |
Use Scenario: Per-port current limiting and fault detection in 48-V PoE++ line cards with hot-swap controllers. IC Role / Device Role / Timing Role: High-common-mode current monitor interfaced to FPGA-based protection logic via buffered ADC. Use Value: Survives 60-V surge events (with INA168 variant) and provides <32 kHz bandwidth for fast overcurrent response. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar high-side current measurement applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| INA168UA/3K | Wider 2.7–60 V common-mode range; otherwise identical pinout, gain structure, and specs. | Required for systems with >36 V rails (e.g., 48-V telecom, EV auxiliary supplies). | Select INA168UA/3K when input common-mode exceeds 36 V; same layout and firmware apply. |
| MAX4080TASA+ | Higher 250 µA/V transconductance; 12-bit integrated ADC option; 5-V-only supply; different pinout. | Suitable for compact, self-contained current telemetry nodes needing digital output. | Choose MAX4080TASA+ only if 5-V supply and digital interface are available; requires PCB redesign. |
Compared with INA138NA/3KG4, INA168UA/3K extends voltage capability without changing design effort, while MAX4080TASA+ trades analog flexibility for integrated digitization - making it viable only when supply and interface constraints align.
Availability
INA138NA/3KG4 is available at Aetrix Electronics and suitable for battery chargers, industrial power supplies, and portable medical devices requiring stable component supply across multi-year production cycles.
Supply support for INA138NA/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 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-common-mode current sensing in space- and energy-constrained systems - targeting battery, telecom, and industrial power applications.
FAQ
What is the maximum common-mode voltage supported by the INA138NA/3KG4?
The INA138NA/3KG4 supports an input common-mode voltage range of 2.7 V to 36 V. This means it can accurately measure current across a shunt resistor placed on power rails up to 36 V, such as in 24-V industrial systems or 32-V telecom supplies. Exceeding 36 V risks damage or inaccurate operation - for higher voltages, the pin-compatible INA168 variant (up to 60 V) must be used instead of INA138NA/3KG4.
How is gain configured on the INA138NA/3KG4?
Gain on the INA138NA/3KG4 is set exclusively by an external load resistor (RL) connected between the OUT pin and ground. The device outputs a current IO = 200 µA/V × (VIN+ – VIN–), so VOUT = IO × RL. For example, a 10-kΩ RL yields 2 V/V gain. No internal resistors or configuration pins are involved - INA138NA/3KG4 requires no programming or trimming to achieve precise, scalable gain.
Can the INA138NA/3KG4 measure bidirectional current?
No - the INA138NA/3KG4 is a unipolar high-side current monitor designed only for positive current flow (VIN+ more positive than VIN–). Attempting reverse polarity results in zero output current, not negative output. To measure bidirectional current, two INA138NA/3KG4 devices must be used in opposing configurations with external logic (e.g., comparator or multiplexer), as documented in TI's SBOS122E datasheet Figure 15. This is a hardware-level limitation of INA138NA/3KG4 itself.
What is the output impedance of the INA138NA/3KG4?
The INA138NA/3KG4 has a very high output impedance - specified as 1 GΩ || 5 pF - because it functions as a precision current source. This allows RL values up to 500 kΩ without significant loading error. However, when driving capacitive loads (e.g., ADC input capacitance), bandwidth drops and step response degrades; TI recommends adding a buffer amplifier (e.g., OPA340) between INA138NA/3KG4 and any ADC to preserve accuracy and speed.
Does the INA138NA/3KG4 require a separate ground connection for the shunt resistor?
Yes - the INA138NA/3KG4 requires a dedicated low-impedance ground connection at Pin 2 (GND) that must be tied to the system ground plane, independent of the shunt resistor's low-side node. VIN– (Pin 4) connects directly to the shunt's low-side terminal, which may sit at elevated potential (e.g., 24 V). Separating GND reference from VIN– ensures accurate differential measurement and prevents ground-loop errors - a critical layout requirement for INA138NA/3KG4 performance.
INA138NA/3KG4 Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- -
- Package/Case:
- SC-74A, SOT-753
- Packaging:
- Tape & Reel (TR)
- Product Status:
- Obsolete
- Function:
- Current Monitor
- Sensing Method:
- High-Side
- Accuracy:
- ±0.5%
- Voltage - Input:
- 2.7V ~ 36V
- Current - Output:
- -
- Operating Temperature:
- -40°C ~ 125°C
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- SOT-23-5
INA138NA/3KG4 FAQ
1.How can I place an order for INA138NA/3KG4 through Aetrix?
Please submit a Request for Quotation (RFQ) for INA138NA/3KG4 on Aetrix. Our sales agent will provide a competitive quotation and guide you through the order confirmation once you accept the terms.
2.Are the price and stock information for INA138NA/3KG4 reliable?
The price and inventory of INA138NA/3KG4 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for INA138NA/3KG4 is usually 5 days.
3.What payment methods are accepted for INA138NA/3KG4?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for INA138NA/3KG4 transactions.
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4.How is shipping managed for INA138NA/3KG4?
INA138NA/3KG4 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your INA138NA/3KG4 order is processed, you will receive an email with the shipment details and tracking number.
Note: Tracking information may take up to 24 hours to appear. Express delivery typically takes 3–5 business days.
5.How can I obtain technical support or documentation for INA138NA/3KG4?
For technical support, including INA138NA/3KG4 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your INA138NA/3KG4 requirements.
6.How does Aetrix verify that INA138NA/3KG4 is sourced from the original manufacturer or authorized distributors?
All INA138NA/3KG4 products on Aetrix are procured from qualified distributors and authorized channels. Our dedicated quality assurance team conducts strict verification, including traceability checks and, if necessary, third-party testing. This ensures that INA138NA/3KG4 meets industry standards.
7.What is the process for return or replacement of INA138NA/3KG4?
All INA138NA/3KG4 units undergo pre-shipment inspection (PSI). If there is an issue with INA138NA/3KG4, returns or replacements are accepted under the following conditions:
1.Quantity discrepancies, incorrect items, or visible external defects (such as breakage or corrosion), acknowledged by Aetrix.
2.The issue is reported within 90 days of delivery.
3.The INA138NA/3KG4 part is unused and in its original packaging.
Return procedure for INA138NA/3KG4:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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