Texas Instruments LM3622AMX-4.2

Overview

LM3622AMX-4.2 from Texas Instruments is a precision lithium-ion battery charge controller IC for single-cell 4.2 V nominal packs, delivering ±30 mV/cell end-of-charge voltage accuracy, 4.5 V–24 V wide input range, and 15 mA EXT pin sink current to drive external PNP pass transistors in constant-voltage/constant-current (CVCC) charging topologies - deployed in cellular phone cradle chargers.

For engineers reviewing the LM3622AMX-4.2 datasheet, LM3622AMX-4.2 pinout, LM3622AMX-4.2 application, or LM3622AMX-4.2 equivalent, key selection considerations include its 2.15 V/cell or 2.70 V/cell user-selectable low-voltage wake-up threshold, <200 nA battery drain during input disconnect, and SOIC-8 package compatibility with linear charger reference designs requiring tight voltage regulation and thermal stability over −20°C to +70°C ambient.

Technical Context

The LM3622AMX-4.2 implements a temperature-compensated bandgap reference for precise 4.200 V ±30 mV/cell regulation and uses an external sense resistor at the CS pin to enforce 100 mV current-limit threshold, enabling accurate constant-current control independent of supply variation. Its internal power-down switch isolates the CEL pin when VCC is removed, limiting battery leakage to 200 nA.

Functional operation integrates CVCC mode switching via feedback from CEL (battery positive) and CS (battery negative/sense) pins, while the EXT pin modulates base drive to an external PNP transistor. Low-voltage detection is enabled via LVENB and threshold selected via LVSEL, producing an NPN open-collector LV output that initiates wake-up charging below preset cell voltage thresholds.

Key Specifications

Pinout & Package

LM3622AMX-4.2 is housed in an 8-lead SOIC (Package Drawing D), surface-mount package with standard 1.27 mm pitch and JEDEC MS-012AC dimensions (4.90 mm × 3.91 mm × 1.75 mm).

Key Features

Applications

Equivalent & Alternatives

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

Compared with BQ2002F and TP4056, the LM3622AMX-4.2 provides superior flexibility in pass-element selection, programmable low-voltage recovery, and wider input voltage tolerance - making it optimal for multi-adapter cradle systems requiring field-reliable wake-up and precision termination without added IC complexity.

Availability

LM3622AMX-4.2 is available at Aetrix Electronics and suitable for cellular phone cradle chargers, PDA/Notebook cradle chargers, and camcorder cradle chargers requiring stable component supply, long-lifecycle support, and RoHS-compliant packaging.

Supply support for LM3622AMX-4.2 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 is a global semiconductor leader delivering analog, embedded processing, and connectivity solutions with emphasis on reliability, scalability, and broad technical support infrastructure.

The LM3622AMX-4.2 belongs to TI's dedicated battery management analog controller product line, designed specifically for cost-effective, high-accuracy linear Li-ion charging in cradle and dock applications where MCU-free operation and analog precision are prioritized.

FAQ

What is the exact charge voltage regulation accuracy of the LM3622AMX-4.2 over temperature?

The LM3622AMX-4.2 delivers ±30 mV/cell end-of-charge voltage accuracy over the full operating ambient temperature range of −20°C to +70°C. This specification is confirmed in the Electrical Characteristics table for the "A" grade device under TJ = 0°C to +70°C conditions, with typical regulation at 4.200 V and limits spanning 4.170 V to 4.230 V - ensuring compliance with JEITA-recommended Li-ion termination tolerances without external calibration.

Does the LM3622AMX-4.2 support two-cell (8.4 V) battery charging?

No, the LM3622AMX-4.2 is specifically configured for single-cell 4.2 V lithium-ion battery charging. It is part of the LM3622 family's 4.2 V variant group; dual-cell versions such as LM3622MX-8.4 are separate orderable parts with distinct internal voltage references and marking. Using LM3622AMX-4.2 on an 8.4 V pack would result in severe undercharging and failure to reach full capacity.

How does the LV pin function during low-voltage wake-up operation in the LM3622AMX-4.2?

In the LM3622AMX-4.2, the LV pin operates as a NPN open-collector output that transitions to low-impedance (sinking up to 10 mA) when LVENB is grounded and the sensed cell voltage falls below the LVSEL-selected threshold (2.15 V/cell or 2.70 V/cell). This signal directly enables an external low-current source - such as a PNP transistor biased via a pull-up resistor - to deliver wake-up charge until the battery recovers above the threshold, at which point LV returns to high-impedance and normal CVCC resumes.

What is the maximum allowable voltage at the EXT pin of the LM3622AMX-4.2 relative to VCC?

The EXT pin voltage must not exceed VCC + 0.3 V in the LM3622AMX-4.2, as specified in the Absolute Maximum Ratings table. Exceeding this limit risks reverse current flow from EXT into VCC, potentially damaging internal circuitry. This constraint applies regardless of whether the EXT pin drives a PNP transistor base or a PMOS gate, and necessitates careful layout to avoid coupling noise or overshoot that could breach the margin.

Can the LM3622AMX-4.2 operate without an external current-sense resistor?

No - the LM3622AMX-4.2 requires an external sense resistor (RCS) between the CS pin and GND to establish the constant-current regulation setpoint. The IC holds the voltage across RCS at 100 mV (typical), so charge current is calculated as I_CHG = 0.1 V / RCS. Omitting RCS disables current limiting and risks uncontrolled charging; no internal sense element exists, and the CS pin has no default functionality without this resistor.