Microchip Technology MIC5249-2.85BMM-TR

Overview

MIC5249-2.85BMM-TR from Micrel is a 300mA, 2.85V fixed-output CMOS low-dropout regulator with programmable power-on-reset delay, ±1.0% initial output accuracy, 340mV dropout at full load, and integrated open-drain RESET output. It serves as a precision voltage source with fault monitoring in battery-powered portable electronics requiring ultra-low noise and fast transient response.

For engineers reviewing the MIC5249-2.85BMM-TR datasheet, MIC5249-2.85BMM-TR pinout, MIC5249-2.85BMM-TR application, or MIC5249-2.85BMM-TR equivalent, key selection criteria include its MSOP-8 package compatibility, ceramic-capacitor stability, adjustable POR delay via external capacitor, and zero-current shutdown mode for energy-sensitive designs.

Technical Context

The MIC5249-2.85BMM-TR integrates a precision bandgap reference, CMOS pass element, and dedicated POR delay circuitry driven by a 0.55µA current source into the DELAY pin. Its active-clamp shutdown discharges the output during disable, while the open-drain RESET output asserts low only when both undervoltage (VOUT < 91% nominal) and internal fault (overcurrent/thermal) conditions coexist.

It achieves 65dB PSRR at 120Hz using a 0.01µF CBYP capacitor to bypass the internal reference, and maintains stability with ≥2.2µF ceramic output capacitance and ≤300mΩ ESR-enabling compact, low-noise power rails in space-constrained RF and digital baseband sections.

Key Specifications

Pinout & Package

Package: 8-pin MSOP (MM), exposed pad not electrically connected, RoHS-compliant.

Key Features

Applications

Equivalent & Alternatives

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

Compared with TPS7A20285PDQNR and MCP1826-285I/DM, the MIC5249-2.85BMM-TR uniquely combines programmable POR delay, open-drain RESET with intelligent fault detection, and reference bypass capability-making it optimal for compact, noise-sensitive, and sequenced-power applications where timing and signal integrity are co-constrained.

Availability

MIC5249-2.85BMM-TR is available at Aetrix Electronics and suitable for cellular phones, fiber optic modules, PDAs, and portable medical sensors requiring stable component supply, long-lifecycle support, and RoHS-compliant packaging.

Supply support for MIC5249-2.85BMM-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. It specialized in high-performance power management, timing, and interface solutions.

The MIC5249 product line delivers precision, low-noise LDOs with integrated power-on-reset for portable and communications equipment-designed specifically to replace discrete reset + regulator combinations in space- and noise-constrained applications.

FAQ

What is the minimum input voltage required for MIC5249-2.85BMM-TR to regulate at full 300mA load?

The MIC5249-2.85BMM-TR requires VIN ≥ VOUT + dropout voltage. With a typical dropout of 340mV at 300mA, the minimum input is 2.85V + 0.34V = 3.19V. At higher temperatures or worst-case process corners, dropout may reach 600mV, so design margin should target VIN ≥ 3.45V for robust operation across all conditions. The MIC5249-2.85BMM-TR datasheet specifies absolute minimum VIN as 2.7V, but regulation cannot be guaranteed below 3.19V under full load.

How does the DELAY pin on MIC5249-2.85BMM-TR set the power-on-reset timeout?

The DELAY pin sources a precise 0.55µA current. When an external capacitor (CDELAY) is connected from DELAY to GND, the voltage ramp across it determines RESET assertion time: TDELAY = CDELAY × 1.4V / 0.55µA. For example, a 47nF capacitor yields ~120ms delay. No capacitor results in immediate RESET assertion upon VIN application. The MIC5249-2.85BMM-TR does not require a resistor in series-the timing is purely capacitive.

Can MIC5249-2.85BMM-TR operate without the CBYP capacitor?

Yes, the MIC5249-2.85BMM-TR functions without the CBYP capacitor, but PSRR degrades significantly-dropping from 65dB to ~45dB at 120Hz-and broadband output noise increases. The CBYP pin is optional but strongly recommended for noise-critical applications like RF transceivers or high-resolution ADCs. Leaving CBYP open does not affect regulation or stability; it only impacts noise performance. The MIC5249-2.85BMM-TR remains fully functional and within spec without it.

What is the purpose of the NC pin (Pin 6) on MIC5249-2.85BMM-TR, and can it be tied to GND?

Pin 6 is a true no-connect (NC) terminal-unbonded internally and electrically isolated. It must remain floating with no solder mask opening, trace, or copper pour. Tying it to GND (or any potential) risks parasitic coupling, mechanical stress on the bond wire, or latent reliability issues. The MIC5249-2.85BMM-TR datasheet explicitly prohibits connection of Pin 6; doing so violates the specified MSOP-8 layout and may compromise long-term performance or ESD robustness.

Does MIC5249-2.85BMM-TR support reverse-voltage protection or input overvoltage clamping?

No, the MIC5249-2.85BMM-TR does not include reverse-voltage protection or input overvoltage clamping. Absolute maximum VIN is +7V; exceeding this risks permanent damage. Reverse polarity on VIN or VOUT is not protected-the internal CMOS pass device lacks body-diode conduction path in reverse direction, but sustained reverse bias can break down gate oxides. System-level protection (e.g., series Schottky diode, TVS, or dedicated protection IC) must be added externally. The MIC5249-2.85BMM-TR relies entirely on proper upstream circuit design for fault tolerance.