Microchip Technology MIC4681-2.5BM TR

Overview

MIC4681-2.5BM TR from Micrel is a fixed-output 2.5V, 200kHz voltage-mode buck regulator in SOP-8 package, delivering up to 1A continuous output current from 4V–30V input. It integrates an NPN power switch, internal compensation, and cycle-by-cycle current limiting, optimized for GSM battery charging and compact high-efficiency DC/DC conversion.

For engineers reviewing the MIC4681-2.5BM TR datasheet, MIC4681-2.5BM TR pinout, MIC4681-2.5BM TR application, or MIC4681-2.5BM TR equivalent, key selection considerations include its fixed 2.5V output, 2.1A minimum current limit, thermal shutdown at 160°C, <6µA shutdown current, and compatibility with standard surface-mount inductors and Schottky diodes in space-constrained designs.

Technical Context

The MIC4681-2.5BM TR implements voltage-mode control using a 1.23V bandgap reference and 200kHz sawtooth oscillator to generate variable-duty-cycle gate drive for its integrated NPN switch. Feedback is taken directly from the output via internal resistor divider (fixed 2.5V version), eliminating external resistors.

Protection includes cycle-by-cycle current limiting (2.2–4.5A short-circuit limit), thermal shutdown at 160°C, and under-voltage lockout inherent in the 4V minimum VIN. Frequency foldback reduces switching frequency to ~60kHz during hard short-circuit conditions to limit power dissipation.

Key Specifications

Pinout & Package

Package: 8-lead SOP (M), power-enhanced variant with exposed die-attach paddle thermally tied to pins 5–8 (GND). Junction-to-ambient thermal resistance θJA = 63°C/W on standard 1"² FR4 board with full GND copper pour.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar buck regulator applications.

Compared with LM2678-2.5/NOPB and TPS54202DR, the MIC4681-2.5BM TR offers simpler implementation with fixed 2.5V output and minimal external parts, making it optimal for cost-sensitive, space-limited GSM and industrial applications where 1A continuous output suffices.

Availability

MIC4681-2.5BM TR is available at Aetrix Electronics and suitable for cellular phone battery chargers, industrial sensor nodes, and POS terminal power supplies requiring stable component supply, long-term lifecycle support, and consistent parametric performance across production batches.

Supply support for MIC4681-2.5BM 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

Micrel, Inc. was a U.S.-based semiconductor company specializing in power management, timing, and interface ICs before its acquisition by Microchip Technology in 2015.

The MIC4681-2.5BM TR belongs to Micrel's SuperSwitcher™ family of integrated buck regulators, designed specifically for high-efficiency, low-component-count DC/DC conversion in portable and industrial power applications.

FAQ

What is the output voltage tolerance of the MIC4681-2.5BM TR over temperature and line/load conditions?

The MIC4681-2.5BM TR delivers a fixed 2.5V output with ±2% initial accuracy. Over –40°C to +125°C junction temperature, 4V–30V input, and 0.1A–1A load, the output remains within ±3% due to internal resistor divider matching and bandgap stability. This is verified in the Electrical Characteristics table under "Feedback Voltage" for adjustable variants and confirmed by application circuit validation at 2.5V.

Can the MIC4681-2.5BM TR be used without an external Schottky diode?

No, the MIC4681-2.5BM TR requires an external Schottky diode (e.g., B340A or SS36) connected between the SW pin and output capacitor. It uses an NPN transistor as the internal switch and lacks a synchronous rectifier, so the diode provides the freewheeling path during the off-time. Omitting it will cause catastrophic failure due to inductive kickback.

What is the minimum recommended ground plane area for reliable 1A operation of the MIC4681-2.5BM TR?

Micrel specifies a minimum 6 cm² copper area connected to pins 5–8 (GND) for reliable 1A continuous operation at 25°C ambient. This ground plane must be on the same PCB layer as the device and provide low-impedance thermal conduction. Larger areas improve thermal margin, especially above 60°C ambient or with higher input voltages.

Does the MIC4681-2.5BM TR support adjustable output voltages?

No, the MIC4681-2.5BM TR is a fixed-output variant configured at the factory for 2.5V. Its FB pin is internally connected to a precision resistor divider; external resistor networks cannot modify the output. For adjustable operation, use the MIC4681BM (adjustable version) with external R1/R2.

How does the MIC4681-2.5BM TR behave during input undervoltage or thermal overload?

The MIC4681-2.5BM TR has no dedicated UVLO circuit, but ceases regulation below ~4V VIN due to internal bias limitations. During thermal overload, it activates thermal shutdown at 160°C junction temperature, halting switching and drawing <6µA until junction cools by ~10°C, then auto-restarts. Current limiting engages first during overload, preventing immediate thermal trip under moderate overloads.