Microchip Technology MIC4681BM-TR

Overview

MIC4681BM-TR from Micrel is a voltage-mode synchronous buck regulator IC with integrated 2.1A NPN switch, operating at fixed 200kHz switching frequency, supporting 4V–30V input and adjustable output down to 1.25V, delivering up to 1A continuous output current in SOP-8 package-designed for GSM battery chargers and high-efficiency step-down power supplies.

For engineers reviewing the MIC4681BM-TR datasheet, MIC4681BM-TR pinout, MIC4681BM-TR application, or MIC4681BM-TR equivalent, key selection criteria include its 200kHz fixed-frequency operation, 1.23V feedback reference tolerance (±1%), thermal shutdown at 160°C, cycle-by-cycle current limiting, and <6µA shutdown quiescent current-critical for pulsed-load and space-constrained industrial/telecom designs.

Technical Context

The MIC4681BM-TR implements voltage-mode PWM control using a 1.23V internal bandgap reference and 200kHz sawtooth oscillator; error amplifier output drives a comparator against the ramp to generate variable-duty-cycle gate drive for the internal NPN switch. It features frequency foldback during short-circuit (down to ~60kHz) to limit energy per cycle.

Protection includes cycle-by-cycle current limiting (2.2–4.5A short-circuit limit), thermal shutdown at 160°C, and under-voltage lockout via SHDN pin with 0.8V/1.25V hysteresis. The device uses external Schottky diode and inductor, requiring no external compensation due to internal compensation network optimized for 68µH inductors and 220µF output capacitors.

Key Specifications

Pinout & Package

Package: 8-lead SOP (SOIC-8) with exposed thermal paddle (pins 5–8 tied to GND); junction-to-ambient thermal resistance θ_JA = 63°C/W with recommended 6 cm² ground plane.

Key Features

Applications

Equivalent & Alternatives

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

Compared with LM2575HVSX-5.0/NOPB and TPS54202DRCT, the MIC4681BM-TR offers superior integration (no compensation needed), lower standby current (<6µA vs. ~10µA), and proven GSM pulse-charge capability-but lacks adjustable frequency and fixed-output variants, making it optimal for cost-sensitive, thermally constrained 1A buck designs requiring rapid time-to-market.

Availability

MIC4681BM-TR is available at Aetrix Electronics and suitable for cellular phone battery chargers, industrial 12V-to-5V buck supplies, and positive-to-negative inverting converters requiring stable component supply, long-lifecycle support, and RoHS-compliant packaging.

Supply support for MIC4681BM-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 Semiconductor (acquired by Microchip in 2015) was a U.S.-based analog and power management IC designer focused on high-performance, easy-to-use power solutions for communications and industrial markets.

The MIC4681BM-TR belongs to Micrel's SuperSwitcher™ family-engineered for plug-and-play buck conversion with minimal external components, targeting GSM chargers, portable electronics, and space-constrained industrial power rails.

FAQ

What is the maximum continuous output current of the MIC4681BM-TR?

The MIC4681BM-TR delivers up to 1A continuous output current at 25°C ambient with a properly designed 6 cm² ground plane. Derating occurs above 25°C or with smaller ground areas; at 60°C ambient and 5V output, max continuous current drops to ~1.4A (per SOA curves). Peak pulsed current reaches 2A for GSM charging cycles, validated at V_IN = 12V and 30V.

Does the MIC4681BM-TR require external compensation components?

No, the MIC4681BM-TR features internal frequency compensation optimized for use with standard 68µH inductors and 220µF output capacitors. This eliminates external compensation networks, reduces BOM count, and guarantees stability across line, load, and temperature-verified with phase margins ≥53° under worst-case conditions (30V_IN, 1.1A load).

What is the feedback reference voltage tolerance of the MIC4681BM-TR?

The MIC4681BM-TR has a 1.230V feedback reference with ±1% tolerance (1.217V–1.243V) over –40°C to +125°C junction temperature. This tight tolerance ensures accurate output voltage setting across temperature and load, critical for battery charging and precision analog supplies.

How does the MIC4681BM-TR behave during a short-circuit condition?

Under hard short-circuit, the MIC4681BM-TR initiates frequency foldback-reducing switching frequency from 200kHz to ~60kHz-to limit energy per cycle and prevent thermal runaway. Combined with cycle-by-cycle current limiting (2.2–4.5A) and thermal shutdown at 160°C, this provides robust fault protection without latch-off.

Can the MIC4681BM-TR be used in an inverting buck-boost configuration?

Yes, the MIC4681BM-TR supports inverting buck-boost topology by grounding the inductor's far end and taking output from the junction of inductor and output capacitor. Application Figure 8 demonstrates –12V/150mA generation from +12V input, leveraging the same 200kHz oscillator and feedback architecture-no hardware changes required beyond external component reconfiguration.