Microchip Technology MIC5249-2.8BMM-TR

Overview

MIC5249-2.8BMM-TR from Micrel is a 300mA, 2.8V fixed-output CMOS low-dropout regulator with programmable power-on-reset delay, ±1.0% initial output accuracy, 340mV dropout at full load, and ultra-low 85µA quiescent current-designed for noise-sensitive battery-powered applications such as cellular handsets and fiber optic modules.

For engineers reviewing the MIC5249-2.8BMM-TR datasheet, MIC5249-2.8BMM-TR pinout, MIC5249-2.8BMM-TR application, or MIC5249-2.8BMM-TR equivalent, key selection criteria include adjustable POR delay via external capacitor, open-drain RESET output with 89–91% VOUT undervoltage threshold, active shutdown clamp, ceramic-capacitor stability, and MSOP-8 thermal performance (θJA = 160°C/W).

Technical Context

The MIC5249-2.8BMM-TR integrates a precision bandgap reference with a CMOS pass element to achieve low dropout and high PSRR (65dB @ 120Hz). Its internal architecture includes an error amplifier, current-limit circuitry, thermal shutdown comparator, and logic-controlled enable path with zero-current shutdown mode.

It implements power-on reset using a dedicated DELAY pin sourcing 0.55µA to charge an external capacitor, generating a user-defined delay before RESET transitions high; the RESET output is open-drain, requiring external pull-up, and asserts low only when both undervoltage detection (VOUT < 89–91% nominal) and fault conditions (overcurrent/overtemperature) coincide.

Key Specifications

Pinout & Package

Package: 8-pin MSOP (MM), 3.0mm × 3.0mm × 1.0mm body, exposed pad optional, RoHS-compliant.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MCP1826-2802E/DB and XC6219B282MR-G, the MIC5249-2.8BMM-TR uniquely combines 300mA capability, programmable POR delay, open-drain RESET with undervoltage hysteresis, and active output discharge-all in an MSOP-8 package optimized for thermal management in space-constrained designs.

Availability

MIC5249-2.8BMM-TR is available at Aetrix Electronics and suitable for cellular handsets, fiber optic modules, PDAs, and portable medical sensors requiring stable component supply, long-term lifecycle support, and consistent parametric performance across temperature.

Supply support for MIC5249-2.8BMM-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, acquired by Microchip Technology in 2015; known for high-performance power management and timing solutions.

The MIC5249 family was designed specifically for noise-critical, battery-powered portable electronics-emphasizing low dropout, ultra-low IQ, ceramic-capacitor stability, and integrated power sequencing features like programmable POR.

FAQ

What is the maximum input voltage for MIC5249-2.8BMM-TR at 300mA output in MSOP-8 package?

The MIC5249-2.8BMM-TR supports up to 4.56V input at 300mA output when ambient temperature is 50°C, based on its 160°C/W junction-to-ambient thermal resistance and 125°C max junction temperature. Exceeding this limit risks thermal shutdown. Derating is required at higher ambient temperatures or with reduced PCB copper area.

Does MIC5249-2.8BMM-TR require an external pull-up resistor on the RESET pin?

Yes, the RESET pin of MIC5249-2.8BMM-TR is an open-drain output and must be pulled up externally-typically to VIN or VOUT-with a resistor between 10kΩ and 100kΩ. Without pull-up, the RESET signal cannot transition high, preventing proper power-on reset signaling in the host system.

Can MIC5249-2.8BMM-TR operate stably with no load connected to VOUT?

Yes, MIC5249-2.8BMM-TR remains stable and in regulation at 0mA load-a key differentiator from many LDOs. This makes it suitable for CMOS RAM keep-alive circuits and always-on sensor biasing where load current may drop to zero during sleep states without risking oscillation or dropout.

What capacitor value is needed on the DELAY pin of MIC5249-2.8BMM-TR to achieve a 100ms POR delay?

Using the formula TDELAY = CDELAY × VDELAY / IDELAY, with VDELAY = 1.4V and IDELAY = 0.55µA, a 100ms delay requires CDELAY ≈ 0.079µF (79nF). A standard 82nF ceramic capacitor yields ~103ms delay. No capacitor results in immediate RESET assertion-functioning as a basic undervoltage flag.

Is the ENABLE pin of MIC5249-2.8BMM-TR compatible with 1.8V logic levels?

No-MIC5249-2.8BMM-TR requires a minimum of 1.6V on the ENABLE pin to guarantee activation, and logic-low must be ≤0.4V to ensure shutdown. While 1.8V GPIO can reliably enable it, 1.2V logic may not meet the VIH threshold; level-shifting is recommended for sub-1.6V control interfaces.