Analog Devices Inc./Maxim Integrated MAX6805US29D3+T

Overview

MAX6805US29D3+T from Maxim Integrated is a 4-pin SOT143 open-drain microprocessor supervisory circuit with 2.93V reset threshold, 100ms minimum reset timeout, and guaranteed operation down to VCC = 1.0V. It monitors power supplies in 2.85V–5.0V digital systems, asserts active-low RESET during brownout or manual reset, and features debounced MR input and transient-immune reset comparator. Used in portable battery-powered equipment for reliable µP power-up sequencing.

For engineers reviewing the MAX6805US29D3+T datasheet, MAX6805US29D3+T pinout, MAX6805US29D3+T application, or MAX6805US29D3+T equivalent, key selection criteria include open-drain output compatibility with bidirectional µP reset pins (e.g., Motorola 68HC11), factory-trimmed 2.93V threshold tolerance (±3% over –40°C to +125°C), 100ms reset timeout stability across temperature, and ultra-low 4µA supply current at 3.0V.

Technical Context

The MAX6805US29D3+T implements a precision bandgap-based reset comparator with factory-trimmed 2.93V threshold and ±3% variation over –40°C to +125°C. Its open-drain RESET output requires an external pullup resistor and supports bidirectional reset interfaces without contention.

Reset assertion is triggered by VCC falling below 2.93V or MR low pulse ≥1µs, with 100ms minimum timeout after VCC recovery or MR deassertion. The device maintains valid RESET state only down to VCC = 1.0V - unlike MAX6803/MAX6804 (guaranteed to 0.7V) - and rejects transients ≤30µs at 10V/ms slew rate.

Key Specifications

Pinout & Package

MAX6805US29D3+T is housed in a 4-pin SOT143 package (U4-1 outline, land pattern 90-0183), measuring 2.9mm × 1.6mm × 1.1mm, RoHS-compliant with lead-free finish (+T suffix).

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar microprocessor reset supervision applications.

Compared with MAX6804US29D3+T, the MAX6805US29D3+T enables shared reset buses and bidirectional µP compatibility; compared with TPS3808G33DBVR, it offers factory-adjustable threshold, MR input, and documented transient immunity - making it preferable for industrial and portable systems demanding design flexibility and noise resilience.

Availability

MAX6805US29D3+T is available at Aetrix Electronics and suitable for portable medical monitors, industrial PLC controllers, handheld test equipment, and smart energy meters requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for MAX6805US29D3+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 industrial, automotive, communications, and computing applications.

The MAX6803/MAX6804/MAX6805 family delivers ultra-low-power, pin-compatible µP reset supervisors with factory-trimmed thresholds and multiple output configurations - targeting space-constrained, battery-sensitive, and noise-prone embedded systems.

FAQ

What is the exact reset threshold voltage of the MAX6805US29D3+T and how tightly is it specified?

The MAX6805US29D3+T has a factory-trimmed nominal reset threshold of 2.93V, with guaranteed tolerance of ±3% over the full operating temperature range of –40°C to +125°C. At +25°C, the threshold is specified as 2.93V ±1.8%, meaning the actual value falls between 2.877V and 2.983V. This precision eliminates need for external calibration and ensures consistent brownout response across environmental conditions in the MAX6805US29D3+T.

Does the MAX6805US29D3+T support manual reset, and what are the electrical requirements for the MR pin?

Yes, the MAX6805US29D3+T includes a debounced manual-reset (MR) input that asserts active-low RESET when pulled low. The MR pin has an internal 20kΩ pullup resistor, so it may be left unconnected if unused. To activate reset, drive MR to ≤0.3×VCC (e.g., ≤0.9V at VCC = 3.0V) for ≥1µs. Glitch immunity is rated at 50ns, and MR deassertion delay is 0.1µs - all verified in the MAX6805US29D3+T datasheet.

Why does the MAX6805US29D3+T specify minimum operating voltage as 1.0V while MAX6803/MAX6804 specify 0.7V?

The MAX6805US29D3+T guarantees correct reset assertion and output behavior down to VCC = 1.0V due to its open-drain output stage design, whereas MAX6803/MAX6804 (push/pull) maintain valid RESET/RESET states down to 0.7V. Below 1.0V, the MAX6805US29D3+T's sinking capability degrades, risking indeterminate RESET state - thus it is not recommended for applications requiring reset validity at VCC < 1.0V, unlike the MAX6805US29D3+T's push/pull counterparts.

What is the purpose of the 100ms reset timeout in the MAX6805US29D3+T, and how stable is it over temperature?

The 100ms minimum reset timeout in the MAX6805US29D3+T ensures the microprocessor and peripheral ICs complete power stabilization and internal initialization before release. Typical timeout is 150ms, with maximum 200ms, and normalized variation is ±20% over –40°C to +125°C per typical operating characteristics graph (toc02). This stability prevents premature release during slow-ramping supplies or cold-temperature startup in the MAX6805US29D3+T.

Can the MAX6805US29D3+T be used with microcontrollers that have bidirectional reset pins, and what external components are required?

Yes, the MAX6805US29D3+T's open-drain RESET output is explicitly designed for interfacing with bidirectional µP reset pins (e.g., Motorola 68HC11). An external pullup resistor (typically 10kΩ–100kΩ to VCC or another rail) is mandatory to establish HIGH state when RESET is not asserted. No additional level shifters, buffers, or debounce circuits are needed - the MR input is internally debounced and the RESET output avoids contention, making the MAX6805US29D3+T ideal for such architectures.