Microchip Technology MIC4680-3.3BM-TR

Overview

MIC4680-3.3BM-TR from Micrel is a fixed-output 3.3V, 1.3A synchronous buck regulator in an 8-pin Power SOIC package, operating at 200kHz with 4V–34V input range and internal compensation. It integrates an NPN power switch, thermal shutdown, cycle-by-cycle current limiting, and delivers up to 90% efficiency in compact on-card power conversion applications.

For engineers reviewing the MIC4680-3.3BM-TR datasheet, MIC4680-3.3BM-TR pinout, MIC4680-3.3BM-TR application, or MIC4680-3.3BM-TR equivalent, key selection criteria include its fixed 3.3V output accuracy (±1%), shutdown quiescent current (<2µA), 200kHz switching frequency stability over temperature, and compatibility with standard 68µH inductors and Schottky diodes in minimal-component buck designs.

Technical Context

The MIC4680-3.3BM-TR implements voltage-mode control using a 1.23V internal bandgap reference and a fixed-gain error amplifier comparing FB voltage to generate duty cycle via PWM comparison with a 200kHz sawtooth oscillator. Its internal NPN switch features 1.4V saturation voltage at 1A and supports frequency foldback during short-circuit conditions to limit energy per cycle.

Thermal management relies on the Power SOIC-8 package's integrated die-attach paddle and pins 5–8 as a unified ground path, achieving θ_JA = 63°C/W with proper PCB ground plane area (≥6 cm²). Shutdown logic is TTL-compatible, with 0.8V/1.6V thresholds and <100µA input current in both states.

Key Specifications

Pinout & Package

Package: 8-pin Power SOIC (M) with exposed thermal paddle connected to pins 5–8 (GND); rated for –40°C to +125°C junction temperature and optimized for high-power dissipation via PCB ground plane conduction.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MP2307DJ-LF-Z and LM2678SX-3.3/NOPB, the MIC4680-3.3BM-TR offers lowest system-level BOM count and simplest layout due to internal NPN switch and full internal compensation - ideal for cost-sensitive, space-constrained 1A designs where 30µA shutdown current and SOIC-8 manufacturability are critical.

Availability

MIC4680-3.3BM-TR is available at Aetrix Electronics and suitable for industrial PLC I/O power, automotive body control modules, and medical point-of-care devices requiring stable component supply and long-term lifecycle support.

Supply support for MIC4680-3.3BM-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 analog and mixed-signal semiconductor company founded in 1978 and acquired by Microchip Technology in 2015; known for high-reliability power management and interface ICs.

The MIC4680 family was designed as an easy-to-use, fully integrated buck regulator platform targeting cost-sensitive, high-volume industrial and automotive applications where minimal external components and SOIC manufacturability were essential.

FAQ

What is the maximum continuous output current of the MIC4680-3.3BM-TR?

The MIC4680-3.3BM-TR delivers up to 1.3A continuous output current under proper thermal conditions - specifically with ≥6 cm² PCB ground plane area connected to pins 5–8 and ambient temperature ≤65°C. At higher ambient temperatures or reduced copper area, current must be derated per the Safe Operating Area curve in the datasheet. The internal current limit triggers at 1.3–2.5A depending on FB voltage and thermal state.

Does the MIC4680-3.3BM-TR require external feedback resistors?

No, the MIC4680-3.3BM-TR does not require external feedback resistors. As a fixed-output variant, its FB pin is internally connected to the 3.3V output node - eliminating the need for an external voltage-divider network. This simplifies layout, improves accuracy, and removes resistor tolerance and temperature drift as error sources. Only the adjustable MIC4680BM variant requires R1/R2.

What is the recommended input capacitor for MIC4680-3.3BM-TR?

The recommended input capacitor for MIC4680-3.3BM-TR is a 15µF, 35V low-ESR tantalum or ceramic capacitor (e.g., AVX TPSE156035R0200) placed as close as possible to pins 2 (IN) and 5–8 (GND). This value ensures adequate high-frequency decoupling and transient response while maintaining stability across the 4V–34V input range. Additional bulk capacitance may be added if input ripple or surge immunity is critical.

Can MIC4680-3.3BM-TR operate with a 5V input supply?

Yes, MIC4680-3.3BM-TR can operate with a 5V input supply - its minimum input voltage is 4V, and VIN(min) = VOUT + 2.5V = 5.8V is only a recommended condition for highest efficiency, not an absolute limit. At 5V input, the device maintains regulation with reduced duty cycle and lower efficiency (~70–75% at 1A), but remains fully functional and protected by thermal shutdown and current limiting.

Is MIC4680-3.3BM-TR RoHS-compliant and lead-free?

Yes, MIC4680-3.3BM-TR is RoHS-compliant and lead-free. The "-TR" suffix denotes tape-and-reel packaging, and the "M" in the package code (SOIC-8 M) indicates the Power SOIC variant qualified to Pb-free reflow profiles. Micrel's Pb-free ordering codes (e.g., MIC4680-3.3YM) confirm full compliance with JEDEC J-STD-020 and RoHS Directive 2011/65/EU.