Texas Instruments LM3420AM5X-8.2

Overview

LM3420AM5X-8.2 from Texas Instruments (formerly National Semiconductor) is a precision shunt-mode lithium-ion battery charge controller IC designed for 2-cell (8.2 V nominal) applications. It integrates a trimmed bandgap reference (±0.5% initial tolerance), internal feedback resistor (176 kΩ), open-emitter NPN output transistor (15 mA drive), and compensation-capable error amplifier - enabling accurate end-of-charge voltage regulation in linear or switching charger topologies.

For engineers reviewing the LM3420AM5X-8.2 datasheet, LM3420AM5X-8.2 pinout, LM3420AM5X-8.2 application, or LM3420AM5X-8.2 equivalent, this page delivers verified technical context, real-world design meaning of key specs, validated SOT23-5 pin functions, confirmed alternative parts with documented differences, and application-specific implementation guidance for Li-ion battery charging systems.

Technical Context

The LM3420AM5X-8.2 operates as a precision shunt regulator in the feedback path of external power stages - sensing battery voltage at its IN pin and sourcing current from its OUT pin to control an optocoupler, linear pass transistor, or switching regulator's feedback node. Its internally compensated error amplifier features externally accessible inverting input (COMP pin) for loop stability tuning via single capacitor networks.

It uses a curvature-corrected bandgap reference delivering ±0.5% regulation voltage accuracy over −40°C to +85°C ambient, with 85 µA quiescent current and 1.0 V typical output saturation voltage at 15 mA load. The device supports external VREG trimming (±10%) using resistors between COMP and IN/GND pins, with Rf = 176 kΩ (min 132 kΩ, max 220 kΩ) confirmed for the -8.2 variant.

Key Specifications

Pinout & Package

SOT23-5 package (NS package code MF05A), 5-pin surface-mount, sub-miniature footprint (2.9 mm × 1.6 mm × 1.1 mm). Pin 1 marked by dot; Pin 5 is NC but must be soldered to PCB for thermal relief.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar lithium-ion battery charge controller applications.

Compared with LM3420M5X-8.2, the LM3420AM5X-8.2 provides higher regulation accuracy critical for medical or industrial certifications; compared with TPS650230RSLR, it offers simpler, lower-cost, analog-only control ideal for dedicated 2-cell charger designs without system PMIC needs.

Availability

LM3420AM5X-8.2 is available at Aetrix Electronics and suitable for portable medical devices, industrial handheld terminals, two-wheel electric mobility systems, and backup power systems requiring stable component supply and long-term production continuity.

Supply support for LM3420AM5X-8.2 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 acquired National Semiconductor in 2011 and maintains full legacy support for the LM3420 series. TI is a global semiconductor leader focused on analog and embedded processing technologies.

The LM3420 product line was engineered specifically for precision, low-power, shunt-mode Li-ion battery charge control - targeting space-constrained, cost-sensitive, and thermally demanding applications where external regulation accuracy and minimal quiescent current are essential.

FAQ

What is the exact regulation voltage tolerance of LM3420AM5X-8.2?

The LM3420AM5X-8.2 has a guaranteed ±0.5% initial regulation voltage tolerance at 25°C, with full-range limits of ±1% over −40°C to +85°C ambient. This is specified in the Electrical Characteristics table for the LM3420A-8.2 variant and confirmed in the "Five Lead Surface Mount Package Information" section of the datasheet (SNVS116C). The 8.2 V nominal output enables accurate 4.1 V/cell termination for 2S Li-ion packs.

Can LM3420AM5X-8.2 drive a MOSFET gate directly?

No, LM3420AM5X-8.2 cannot drive a MOSFET gate directly because its OUT pin is an open-emitter NPN transistor that sinks current - it does not source voltage or provide rail-to-rail swing. It requires an external pull-up resistor or level-shifting stage (e.g., PNP transistor or optocoupler) to interface with standard N-channel MOSFET gates. The datasheet explicitly shows Q2 base drive in Figure 5 and gate control via optocoupler in Figure 7.

What is the purpose of Pin 5 (NC) on LM3420AM5X-8.2?

Pin 5 on LM3420AM5X-8.2 is a no-connect terminal with no internal silicon connection, but it serves as a thermal pad. The datasheet states it "should be soldered to PC board for best heat transfer." It must be tied to a copper pour or thermal plane to dissipate power and maintain junction temperature within the 125°C limit - especially under sustained 15 mA output current conditions.

How does LM3420AM5X-8.2 differ from LM3420AM5-8.2?

The LM3420AM5X-8.2 differs from LM3420AM5-8.2 solely in packaging quantity: "M5X" denotes 3000-unit tape-and-reel packaging, while "M5" indicates 1000-unit tape-and-reel. Both share identical electrical specifications, SOT23-5 package dimensions, marking (D07A), and performance characteristics. No functional, parametric, or reliability differences exist between the two orderable variants.

Is external compensation required for stable operation of LM3420AM5X-8.2?

Yes, external compensation is required for stable closed-loop operation of LM3420AM5X-8.2. The COMP pin is the error amplifier's inverting input and must be connected - typically via a capacitor (CC) from COMP to OUT - to set dominant pole frequency and ensure phase margin. The datasheet provides recommended values (e.g., 100 pF for 4.2 V version) and warns that omitting compensation risks oscillation, especially during CC-to-CV transition in battery charging.