Analog Devices Inc./Maxim Integrated MAX6805US29D3

Overview

MAX6805US29D3 from Maxim Integrated is an open-drain, active-low microprocessor supervisory circuit in a 4-pin SOT143 package, designed to monitor 2.93V power supplies and assert reset during brownout, power-up, or manual reset events. It features a factory-trimmed 2.93V reset threshold, 100ms minimum reset timeout, guaranteed operation down to VCC = 1.0V, and 4.0µA supply current - ideal for battery-powered controllers and portable instrumentation.

For engineers reviewing the MAX6805US29D3 datasheet, MAX6805US29D3 pinout, MAX6805US29D3 application, or MAX6805US29D3 equivalent, key selection criteria include its open-drain RESET output for bidirectional µP interface compatibility (e.g., Motorola 68HC11), immunity to fast VCC transients (<30µs at 10V/ms), and precise ±3% threshold tolerance over -40°C to +125°C.

Technical Context

The MAX6805US29D3 implements a precision bandgap-based voltage comparator with factory-trimmed 2.93V threshold and ±3% accuracy across full temperature range. Its reset assertion logic combines VCC monitoring and debounced manual-reset input (MR), with internal 20kΩ MR pullup and 1µs minimum MR pulse width requirement.

Reset remains asserted for ≥100ms after VCC rises above 2.93V or MR deasserts. The open-drain RESET output supports external pullup configurations and interfaces directly with bidirectional µP reset pins without level-shifting - unlike push/pull variants (MAX6803/MAX6804) which require no external pullup but lack this flexibility.

Key Specifications

Pinout & Package

MAX6805US29D3 is housed in a 4-pin SOT143 surface-mount package (outline 21-0052, land pattern 90-0183), measuring 2.9mm × 1.6mm × 1.1mm, optimized for space-constrained embedded systems.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MAX6804US29D3-T, MAX6805US29D3 offers open-drain flexibility for multi-device reset buses but sacrifices 0.3V lower VCC operational margin; versus TPS3808G33DBVR, it provides programmable threshold selection and smaller footprint but lacks watchdog capability and consumes 2.7× more current.

Availability

MAX6805US29D3 is available at Aetrix Electronics and suitable for portable medical sensors, industrial PLC I/O modules, Motorola 68HC11-based controllers, and low-power wireless sensor nodes requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for MAX6805US29D3 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 high-reliability semiconductor solutions for industrial, automotive, and computing markets.

The MAX6803/MAX6804/MAX6805 family delivers cost-optimized, ultra-low-power µP supervisory functions targeting space-constrained and battery-sensitive applications where external component elimination and guaranteed reset validity are critical.

FAQ

What is the factory-trimmed reset threshold voltage for MAX6805US29D3?

The MAX6805US29D3 has a factory-trimmed reset threshold of 2.93V, specified with ±3% tolerance over the full -40°C to +125°C operating temperature range. This value is confirmed in Table 1 of the official datasheet and corresponds to the "29" suffix in the part number. The threshold is set using laser trimming during production and does not require external calibration. At 25°C, the typical value is exactly 2.93V, and the device maintains this accuracy under varying load and supply conditions.

Does MAX6805US29D3 require an external pullup resistor on the RESET pin?

Yes, MAX6805US29D3 requires an external pullup resistor on the RESET pin because it features an open-drain output structure. The datasheet recommends a 100kΩ pullup to VCC for standard interfacing, especially when connecting to bidirectional µP reset pins like those on the Motorola 68HC11. Without this resistor, the RESET signal cannot achieve a defined logic-high state. The internal circuitry does not provide pullup capability, and omission results in undefined reset behavior during non-asserted periods.

What is the minimum VCC voltage at which MAX6805US29D3 guarantees correct reset assertion?

MAX6805US29D3 guarantees correct reset assertion down to VCC = 1.0V at -40°C to +125°C, and down to 1.2V across the full temperature range. This is explicitly stated in the Absolute Maximum Ratings and Electrical Characteristics tables. Unlike the MAX6803/MAX6804 variants (guaranteed to 0.7V), the MAX6805US29D3's open-drain architecture limits its low-VCC operational margin. Below 1.0V, reset validity is not assured, and the device may fail to assert RESET even during brownout.

How does the manual-reset (MR) input function on MAX6805US29D3?

The MR input on MAX6805US29D3 is an active-low, debounced signal with an internal 20kΩ pullup resistor to VCC. When MR is pulled to GND (≤0.3×VCC), reset is immediately asserted and held for ≥100ms after MR returns high. The datasheet specifies a 1µs minimum pulse width and 50ns glitch immunity. If unused, MR may be left floating or tied to VCC - no external components are needed. This simplifies board design compared to supervisors requiring external debounce RC networks.

What package type and dimensions does MAX6805US29D3 use?

MAX6805US29D3 uses a 4-pin SOT143 package (outline 21-0052, land pattern 90-0183), measuring 2.9mm × 1.6mm × 1.1mm. It is available in both leaded and lead-free versions, with lead-free denoted by replacing "-T" with "+T" in the order code. Tape-and-reel packaging is standard, with minimum order quantities of 2500 pieces for standard versions. The small footprint supports high-density PCB layouts common in portable and industrial edge devices.