Microchip Technology MIC5259-1.8BD5-TR

Overview

MIC5259-1.8BD5-TR from Micrel is a 300mA, 1.8V fixed-output CMOS low-dropout regulator optimized for RF and battery-powered systems. It delivers 1.5% initial output accuracy, 300mV dropout at full load, and ultra-low 30µV(rms) output noise with a dedicated noise-bypass pin. Its TTL-compatible enable input and 105µA quiescent current support energy-sensitive portable electronics.

For engineers reviewing the MIC5259-1.8BD5-TR datasheet, MIC5259-1.8BD5-TR pinout, MIC5259-1.8BD5-TR application, or MIC5259-1.8BD5-TR equivalent, key selection criteria include PSRR performance at low VIN, ceramic capacitor stability, active shutdown discharge capability, and thermal behavior in the 5-pin Thin SOT-23 package.

Technical Context

The MIC5259-1.8BD5-TR employs a CMOS pass element with internal reference bypassing via the BYP pin, enabling sub-30µV(rms) noise performance when paired with a 0.01µF capacitor. Its high PSRR (70dB @ 1kHz) is maintained down to VIN = VOUT + 0.3V, critical for weak-battery operation.

It integrates active-clamp shutdown that discharges the output capacitor, fast transient response via high-bandwidth error amplifier, and thermal shutdown with 150°C trip and 10°C hysteresis. The enable logic is TTL-compatible (VIH ≥ 1.6V, VIL ≤ 0.4V), and the device remains stable with no load - essential for CMOS RAM keep-alive circuits.

Key Specifications

Pinout & Package

Package: 5-pin Thin SOT-23 (D5), 2.9mm × 1.6mm footprint, 1.1mm height, JEDEC MO-178 variant. Thermal resistance θJA = 235°C/W on standard PCB layout.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar low-noise LDO applications.

Compared with TPS7A2018PDQNR and MCP1703T-1802E/MB, the MIC5259-1.8BD5-TR uniquely combines 30µV(rms) noise, active output discharge, and 300mV dropout in a 5-pin SOT-23 - making it optimal for space-constrained, battery-fed RF and precision analog systems demanding both cleanliness and controllability.

Availability

MIC5259-1.8BD5-TR is available at Aetrix Electronics and suitable for cellular transceiver bias, portable MCU core supply, and industrial handheld data logger applications requiring stable component supply across extended temperature and long production lifecycles.

Supply support for MIC5259-1.8BD5-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 power management semiconductor company founded in 1978 and acquired by Microchip Technology in 2015. Known for high-performance LDOs, Ethernet PHYs, and timing solutions.

The MIC5259-1.8BD5-TR belongs to Micrel's µCap LDO family, engineered specifically for ultra-low-noise, high-PSRR regulation in RF, portable, and battery-critical applications - emphasizing ceramic capacitor compatibility and minimal board footprint.

FAQ

What is the minimum input voltage required for stable operation of the MIC5259-1.8BD5-TR?

The MIC5259-1.8BD5-TR requires a minimum input voltage of 2.7V per its operating rating. At full 300mA load, it maintains regulation with only 300mV headroom - meaning 2.1V is sufficient *if* the device is operating within its specified dropout behavior. However, the absolute minimum VIN is 2.7V to guarantee all electrical characteristics, including PSRR and noise performance, across temperature and process variation.

Does the MIC5259-1.8BD5-TR require an external bypass capacitor on the BYP pin?

The MIC5259-1.8BD5-TR does not require the BYP pin to be used - it functions correctly with BYP left open. However, connecting a 0.01µF capacitor from BYP to GND reduces output noise from ~45µV(rms) to 30µV(rms) and improves PSRR by up to 15dB. For RF or precision analog applications, this capacitor is strongly recommended and part of the typical application circuit.

Can the MIC5259-1.8BD5-TR remain stable with no load connected to the OUT pin?

Yes, the MIC5259-1.8BD5-TR is explicitly designed for no-load stability and maintains regulation with zero output current. This feature is confirmed in the Application Information section and is critical for applications such as CMOS RAM keep-alive circuits, RTC backup supplies, or systems where downstream circuitry may be fully powered down while the LDO remains enabled.

What is the purpose of the active shutdown clamp in the MIC5259-1.8BD5-TR?

The active shutdown clamp in the MIC5259-1.8BD5-TR is an integrated N-channel MOSFET that connects the OUT pin to GND when the EN pin is driven low. This rapidly discharges the output capacitor and any attached load capacitance, preventing floating voltages, unintended logic states, or latch-up in downstream circuitry - a key requirement for reliable power sequencing in multi-rail embedded systems.

Which ceramic capacitor dielectrics are recommended for use with the MIC5259-1.8BD5-TR output?

X7R and X5R dielectric ceramic capacitors are recommended for the MIC5259-1.8BD5-TR output. These offer stable capacitance over temperature (±15% for X7R), low ESR (<300mΩ), and sufficient volumetric efficiency. Y5V and Z5U dielectrics are discouraged due to >50% capacitance loss over temperature, which risks violating the minimum 1.0µF stability requirement under worst-case conditions.