Microchip Technology MIC5318-1.8YD5-TR

Overview

MIC5318-1.8YD5-TR from Micrel is a fixed-output 1.8V ultra-low dropout (ULDO™) linear regulator delivering 300mA output current with 110mV dropout at full load, 30µV_RMS output noise, and ±2% initial voltage accuracy - designed for RF-sensitive portable electronics requiring stable low-noise biasing.

For engineers reviewing the MIC5318-1.8YD5-TR datasheet, MIC5318-1.8YD5-TR pinout, MIC5318-1.8YD5-TR application, or MIC5318-1.8YD5-TR equivalent, key selection criteria include its 2.3V–6.0V input range, 85µA quiescent current, zero-off-mode shutdown, ceramic-capacitor stability, and 5-pin Thin SOT23-5 package footprint.

Technical Context

The MIC5318-1.8YD5-TR implements a CMOS-based LDO architecture with integrated error amplifier, thermal shutdown, and current limiting. Its quick-start bypass circuit enables fast turn-on (<35µs) even with a 0.01µF BYP capacitor, while maintaining high PSRR (>70dB @ 1kHz) and low noise performance across –40°C to +125°C junction temperature.

It operates as a single-stage, fixed-output regulator with active-high enable control and no internal feedback divider - output voltage is factory-trimmed to 1.8V. The device draws only 0.01µA in shutdown and remains stable with no load, supporting keep-alive applications for CMOS RAM and low-power microcontrollers.

Key Specifications

Pinout & Package

Package: 5-pin Thin SOT23-5 (D5), 2.9mm × 1.6mm × 1.1mm body, exposed pad not electrically connected - optimized for space-constrained portable designs.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MCP1700T-1802E/TT and XC6206P182MR-G, the MIC5318-1.8YD5-TR uniquely combines 300mA drive, 110mV dropout, 30µV_RMS noise, and dedicated BYP/EN pins in a standard SOT23-5 - making it the only option among the three qualified for RF-sensitive, battery-critical portable designs.

Availability

MIC5318-1.8YD5-TR is available at Aetrix Electronics and suitable for GPS receivers, mobile phone baseband subsystems, and portable medical sensors requiring stable component supply, long-term lifecycle support, and RoHS-compliant packaging.

Supply support for MIC5318-1.8YD5-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 semiconductor company specializing in analog, power management, and timing solutions before its acquisition by Microchip Technology in 2015; known for high-performance LDOs and Ethernet PHYs.

The MIC5318 product line delivers ultra-low-noise, ultra-low-dropout regulation for RF and battery-powered portable electronics - engineered specifically for signal integrity in GPS, cellular, and imaging applications where PSRR and output noise directly impact system-level performance.

FAQ

What is the maximum input voltage rating for the MIC5318-1.8YD5-TR?

The MIC5318-1.8YD5-TR has an absolute maximum input voltage of +6.5V, but its recommended operating input range is +2.3V to +6.0V. Exceeding 6.0V may trigger internal protection or cause reliability issues. For sustained operation, VIN should remain within the specified range to ensure ±2% output accuracy and thermal safety across –40°C to +125°C junction temperatures. The MIC5318-1.8YD5-TR is commonly used with 3.3V or 3.6V battery sources.

Does the MIC5318-1.8YD5-TR require an external bypass capacitor on the BYP pin?

Yes - a 0.01µF capacitor from BYP to GND is recommended to achieve the specified 30µV_RMS output noise. Without it, noise increases significantly. The MIC5318-1.8YD5-TR's quick-start circuit allows this capacitor to be added without degrading turn-on time. Larger values (e.g., 0.1µF) further reduce noise and improve PSRR but slightly increase startup delay. Leaving BYP open is permissible but sacrifices low-noise performance.

Can the MIC5318-1.8YD5-TR operate without any load connected to its output?

Yes - the MIC5318-1.8YD5-TR remains stable and in regulation with zero load, a feature uncommon in many LDOs. This makes it suitable for CMOS RAM keep-alive circuits and always-on sensor bias rails. Ground current stays at ~85µA regardless of load, and output voltage holds within ±2% accuracy even at 0mA. This behavior is confirmed in the datasheet's "No-Load Stability" section and typical characteristics plots.

What is the thermal resistance (θ_JA) of the MIC5318-1.8YD5-TR in its SOT23-5 package?

The MIC5318-1.8YD5-TR in the 5-pin Thin SOT23-5 (D5) package has a junction-to-ambient thermal resistance (θ_JA) of 235°C/W under standard JEDEC test conditions. This value assumes minimal copper pour; adding a 100mm² thermal pad under the exposed area can reduce θ_JA by ~30°C/W. At 300mA and 1.8V output from a 3.3V input, power dissipation is ~0.45W - requiring careful thermal layout to stay within the –40°C to +125°C junction limit.

Is the MIC5318-1.8YD5-TR pin-compatible with other members of the MIC5318 family in the same package?

Yes - all MIC5318 variants in the Thin SOT23-5 (D5) package share identical pinout: Pin 1 = EN, Pin 2 = GND, Pin 3 = IN, Pin 4 = OUT, Pin 5 = BYP. Fixed-output versions (e.g., MIC5318-1.5YD5, MIC5318-2.8YD5) and the adjustable MIC5318YD5 use the same pin mapping. However, the MIC5318-1.8YD5-TR is not pin-compatible with the 6-pin Thin MLF® (MT) variants due to different pin count and layout.