Microchip Technology MIC5249-1.8BMM-TR

Overview

MIC5249-1.8BMM-TR from Micrel is a 300mA, 1.8V 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. It integrates an open-drain RESET output, CMOS-compatible ENABLE pin, and noise-reduction bypass input-designed for battery-powered handheld devices requiring stable, low-noise 1.8V supply for baseband processors or RF ICs.

For engineers reviewing the MIC5249-1.8BMM-TR datasheet, MIC5249-1.8BMM-TR pinout, MIC5249-1.8BMM-TR application, or MIC5249-1.8BMM-TR equivalent, key selection factors include its MSOP-8 footprint compatibility, adjustable POR delay via external capacitor, ceramic-capacitor stability, thermal shutdown protection, and active-clamp shutdown discharge capability.

Technical Context

The MIC5249-1.8BMM-TR implements a CMOS-based LDO architecture with internal reference bypass (CBYP), enabling <0.01µF noise-filtering capacitor support. Its RESET output is open-drain, triggered by undervoltage detection AND fault conditions (overcurrent/overtemperature), with 89–91% VOUT low-threshold and 93–96% VOUT high-threshold hysteresis.

Power-on-reset delay is set externally via DELAY pin current source (0.55µA) and threshold (1.40V), allowing precise timing control independent of input ramp rate. The device maintains regulation down to zero load and supports input voltages from +2.7V to +6V while delivering 1.8V ±1.0% over –40°C to +125°C.

Key Specifications

Pinout & Package

Package: 8-pin MSOP (MM), 3.0mm × 3.0mm × 1.0mm body, 0.65mm pitch, exposed pad not electrically connected.

Key Features

Applications

Equivalent & Alternatives

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

Compared with TPS7A0518PDBVR and AP2204-18SRG-7, the MIC5249-1.8BMM-TR uniquely integrates POR delay tuning, open-drain RESET with fault-hysteresis, and reference bypass-making it the only option among the three that satisfies simultaneous low-noise, sequenced-power-up, and active-discharge requirements in compact portable designs.

Availability

MIC5249-1.8BMM-TR is available at Aetrix Electronics and suitable for cellular phones, optical transceivers, and portable diagnostic devices requiring stable component supply, long-term manufacturability, and guaranteed parametric compliance across –40°C to +125°C.

Supply support for MIC5249-1.8BMM-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 and acquired by Microchip Technology in 2015; known for high-performance power management and timing solutions.

The MIC5249 family was designed specifically for noise-sensitive, battery-operated portable electronics-emphasizing ultra-low IQ, ceramic-capacitor compatibility, and integrated power sequencing features in miniature MSOP packages.

FAQ

What is the minimum input voltage required for MIC5249-1.8BMM-TR to regulate at full 300mA load?

The MIC5249-1.8BMM-TR requires VIN ≥ VOUT + dropout voltage. With a typical dropout of 340mV at 300mA, the minimum input is 1.8V + 0.34V = 2.14V. Absolute minimum operating VIN is specified as +2.7V per datasheet-so 2.14V is theoretical; design must use ≥2.7V to guarantee performance across temperature and process variation. The MIC5249-1.8BMM-TR meets all specifications only within its stated operating range of +2.7V to +6V.

Does MIC5249-1.8BMM-TR require an external pull-up resistor on the RESET pin?

Yes-the RESET pin is an open-drain output and must be pulled up externally to either VIN or VOUT using a resistor (typically 10kΩ–100kΩ). Without this pull-up, the RESET signal cannot transition high and will remain indeterminate. This is explicitly required in the MIC5249-1.8BMM-TR functional description and application notes to ensure proper reset signaling during power-up and fault recovery.

Can MIC5249-1.8BMM-TR operate without any load connected to VOUT?

Yes-the MIC5249-1.8BMM-TR remains stable and in regulation with zero load, unlike many older LDO architectures. This is confirmed in the "No-Load Stability" section of the datasheet and enables use in CMOS RAM keep-alive, RTC backup, or other always-on low-power rails where continuous regulation is required even when downstream circuitry is inactive. The MIC5249-1.8BMM-TR maintains 1.8V ±1.0% accuracy under no-load conditions.

What capacitor value on the DELAY pin yields a 200ms power-on-reset delay for MIC5249-1.8BMM-TR?

Using the formula TDELAY = CDELAY × VDELAY / IDELAY, with VDELAY = 1.40V and IDELAY = 0.55µA, a 200ms delay requires CDELAY = (200ms × 0.55µA) / 1.40V = 78.6nF. A standard 82nF ceramic capacitor achieves ~209ms delay. This calculation applies directly to the MIC5249-1.8BMM-TR and is validated in the "DELAY Pin Input" section of the official datasheet.

Is the NC pin (Pin 6) on MIC5249-1.8BMM-TR safe to connect to ground or leave floating?

Pin 6 is designated NC (No Connect) and is not internally bonded-it must remain unconnected. Neither grounding nor routing this pin is permitted. Doing so may cause unpredictable behavior or damage due to potential internal floating node coupling. The MIC5249-1.8BMM-TR datasheet explicitly states "must remain unconnected," and Micrel's package drawings confirm no die bond wire connects to this pad.