Microchip Technology MIC79050-4.2BS TR

Overview

MIC79050-4.2BS TR from Microchip Technology is a fixed-output 4.2 V linear lithium-ion battery charger IC with ±0.75% voltage accuracy over –5°C to +60°C, 380 mV dropout at 500 mA, and zero off-mode current. It integrates an on-chip PNP pass transistor and delivers precise constant-voltage termination for single-cell Li-ion batteries in portable power management systems.

For engineers reviewing the MIC79050-4.2BS TR datasheet, MIC79050-4.2BS TR pinout, MIC79050-4.2BS TR application, or MIC79050-4.2BS TR equivalent, this page provides verified technical context, package-specific pin mapping, real-world charging use cases, and validated alternative parts for Li-ion charge control in space-constrained, thermally sensitive designs.

Technical Context

The MIC79050-4.2BS TR implements a high-accuracy linear regulation architecture using an internal bandgap reference (40 ppm/°C tempco) and error amplifier to control a PNP pass element. Its feedback loop supports external manipulation via the FB pin for pulse charging or shutdown, while thermal shutdown and current-limit protection operate independently of enable state.

Unlike switching chargers, it requires no inductor and achieves stable Li-ion termination with only one external capacitor (4.7 µF). The SOT-223-3 package variant lacks EN and FB pins-making it a true 3-terminal solution-but retains full thermal shutdown, reverse-leakage suppression (<10 µA), and 16 V input tolerance.

Key Specifications

Pinout & Package

Package: SOT-223-3 (thermally enhanced, lead-free, RoHS-compliant); tab internally connected to GND for improved heat transfer.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar lithium-ion linear charger applications.

Compared with MCP73831T-420I/OT and TPS650231RSLR, the MIC79050-4.2BS TR offers the lowest component count (0 external resistors), smallest footprint (SOT-223), and highest voltage accuracy (±0.75% vs. ±1.0% typical), making it optimal for cost-sensitive, space-constrained Li-ion termination where current is set by source impedance rather than IC configuration.

Availability

MIC79050-4.2BS TR is available at Aetrix Electronics and suitable for smartphone charging circuits, wearable battery management, self-charging power banks, and PDA/handheld terminal chargers requiring stable component supply across production lifecycles.

Supply support for MIC79050-4.2BS TR 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

Microchip Technology is a U.S.-based semiconductor company specializing in microcontrollers, analog devices, and power management ICs, with broad industrial and automotive qualification coverage.

The MIC79050 product line delivers highly accurate, thermally robust linear Li-ion chargers optimized for cost-sensitive portable electronics where minimal external components and guaranteed termination voltage accuracy are mandatory.

FAQ

What is the maximum input voltage rating for the MIC79050-4.2BS TR?

The MIC79050-4.2BS TR has an absolute maximum input voltage rating of +20 V, with recommended operating range from +2.5 V to +16 V. Operation within the +2.5 V to +16 V range ensures specified performance including ±0.75% battery voltage accuracy and thermal shutdown functionality. Exceeding +20 V risks permanent damage per Microchip's Absolute Maximum Ratings table.

Does the MIC79050-4.2BS TR require external components to function as a complete charger?

Yes, the MIC79050-4.2BS TR requires only one external component: a 4.7 µF output capacitor on the BAT pin. Unlike many competing chargers, it needs no feedback resistors, current-sense elements, or timing capacitors. Its SOT-223-3 package omits EN and FB pins, making it a true 3-terminal solution ideal for minimalist designs where the MIC79050-4.2BS TR handles both regulation and protection autonomously.

How does the MIC79050-4.2BS TR prevent reverse current flow when the input is disconnected?

The MIC79050-4.2BS TR limits reverse leakage to ≤10 µA when the IN pin is floating or grounded, protecting the Li-ion cell from discharge through the charger. This is achieved via internal circuitry that blocks conduction from BAT to IN under reverse-bias conditions - a key differentiator from basic LDOs. Test data in Figure 2-14 confirms <10 µA leakage at 4.2 V BAT and 25°C, directly supporting long-term storage requirements.

Can the MIC79050-4.2BS TR be used with a 5 V USB power source?

Yes, the MIC79050-4.2BS TR is fully compatible with standard 5 V USB sources. With its 380 mV dropout at 500 mA, it maintains 4.2 V output regulation even as USB voltage sags to 4.6 V under load. Its 2.5 V minimum input allows operation down to weak or aged USB ports, and its thermal shutdown protects against sustained 500 mA operation in confined enclosures - all confirmed in the MIC79050-4.2BS TR's Electrical Characteristics table and thermal curves.

What is the thermal resistance (θ_JA) of the MIC79050-4.2BS TR in its SOT-223 package?

The MIC79050-4.2BS TR in SOT-223 has a junction-to-ambient thermal resistance (θ_JA) of 62°C/W, measured on a standard 1-inch² double-sided PCB with 2 oz copper. This value assumes the exposed tab is soldered to a solid ground plane - critical for achieving rated 500 mA output. Derating is required above +40°C ambient; for example, at +60°C ambient, max continuous output drops to ~380 mA to maintain T_J ≤ +125°C.