Analog Devices Inc./Maxim Integrated MAX8868EUK29+T

Overview

MAX8868EUK29+T from Maxim Integrated is a low-noise, low-dropout linear regulator with 2.84V preset output, 150mA output current capability, 30µVRMS output noise, and 165mV dropout at full load. It features auto-discharge on shutdown, reverse battery protection, and operates from 2.5V to 6.5V input - ideal for space-constrained battery-powered handheld instruments and PCMCIA cards.

For engineers reviewing the MAX8868EUK29+T datasheet, MAX8868EUK29+T pinout, MAX8868EUK29+T application, or MAX8868EUK29+T equivalent, key selection criteria include guaranteed 2.84V ±1.4% output accuracy, 10nA shutdown current, thermal/short-circuit protection, BP-pin noise filtering, and SOT23-5 regular package compatibility with MAX8863/MAX8864 footprints.

Technical Context

The MAX8868EUK29+T uses an internal P-channel MOSFET pass transistor (1.1Ω typical R_DS(ON)) enabling ultra-low quiescent current (100µA across all load and dropout conditions) and eliminating base-drive losses inherent in PNP-based regulators. Its error amplifier compares a 1.25V bandgap reference against feedback from an internal resistor divider tied to OUT.

Unlike the MAX8867, the MAX8868EUK29+T integrates active auto-discharge via an internal NMOS switch between OUT and GND during SHDN assertion, reducing output voltage to ground within microseconds. The BP pin connects to an internal 200kΩ resistor forming an 80Hz low-pass filter with a 0.01µF external capacitor to suppress reference noise.

Key Specifications

Pinout & Package

SOT23-5 regular package (JEDEC MO-178AA), 2.9mm × 1.6mm × 1.1mm body, GND pin serves as thermal pad - requires soldering to large copper area for thermal management.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MAX8867EUK29+T, the MAX8868EUK29+T adds essential auto-discharge without sacrificing noise, dropout, or quiescent current - making it the default choice for new designs. Versus MCP1700T-2802E/TT, it trades minor noise improvement for comprehensive protection features required in certified consumer electronics.

Availability

MAX8868EUK29+T is available at Aetrix Electronics and suitable for hand-held instruments, PCMCIA cards, cellular telephones, and electronic planners requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for MAX8868EUK29+T 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

Maxim Integrated (now part of Analog Devices) designs precision analog, mixed-signal, and power management ICs for demanding industrial, medical, and portable applications.

The MAX8867/MAX8868 product line delivers ultra-low-noise, low-quiescent-current LDOs optimized specifically for battery-powered handheld equipment where runtime, reliability, and small size are critical.

FAQ

What is the exact output voltage tolerance of the MAX8868EUK29+T?

The MAX8868EUK29+T has a factory-preset output voltage of 2.84V with guaranteed accuracy of ±1.4% over the full -40°C to +85°C operating temperature range. This specification is 100% production tested at +25°C and correlation-validated across temperature using Statistical Quality Control methods - ensuring consistent performance in battery-powered handheld instruments and PCMCIA cards where voltage stability directly impacts ADC resolution and logic margin.

Does the MAX8868EUK29+T require an external BP capacitor, and what happens if it's omitted?

Yes, the MAX8868EUK29+T requires a 0.01µF ceramic capacitor between BP and GND to achieve its specified 30µVRMS output noise. Omitting this capacitor increases output noise by ~2× (to ~60µVRMS) due to unfiltered bandgap reference noise coupling into the error amplifier. The device remains functional without it, but noise-sensitive applications like RF synthesizer supplies or precision ADC references will suffer degraded SNR - making the BP capacitor mandatory for designs leveraging the MAX8868EUK29+T's low-noise advantage.

How does the auto-discharge function operate in the MAX8868EUK29+T during shutdown?

When the SHDN pin is pulled low, the MAX8868EUK29+T activates an internal NMOS transistor between OUT and GND, providing a controlled discharge path. This reduces the output voltage to ground within microseconds - confirmed by the "MAX8868 ENTERING SHUTDOWN" waveform in the datasheet (Figure MAX8867/8-25). Unlike passive RC decay, this active discharge prevents floating outputs that could cause unintended wake-up or latch-up in downstream logic, making the MAX8868EUK29+T especially valuable in multi-rail portable systems where sequencing and isolation are critical.

Can the MAX8868EUK29+T be used with input voltages below 2.5V?

No - the MAX8868EUK29+T has an absolute minimum input voltage rating of 2.5V, and its operational specifications (including dropout, noise, and regulation) are only guaranteed for VIN ≥ 2.5V. Attempting to operate below this threshold risks loss of regulation, increased noise, and potential instability. For sub-2.5V battery inputs (e.g., single NiMH or deeply discharged Li-ion), a different regulator such as the MAX8526 series is required - the MAX8868EUK29+T is strictly intended for 2.5V–6.5V input systems like dual-alkaline or standard Li-ion packs.

Is the MAX8868EUK29+T pin-compatible with the MAX8864 series?

Yes, the MAX8868EUK29+T is pin-compatible with the MAX8863 and MAX8864 in SOT23-5 packages, except for the BP pin function. While MAX8863/MAX8864 lack the BP pin entirely, the MAX8868EUK29+T repurposes pin 5 as BP (bypass) instead of NC - meaning direct replacement requires routing the BP capacitor and verifying noise requirements. For drop-in substitution without layout change, MAX8867EUK29+T (same pinout, no BP) is recommended; the MAX8868EUK29+T offers enhanced performance at the cost of minor board modification.