Analog Devices Inc./Maxim Integrated MAX6805US31D3

Overview

MAX6805US31D3 from Maxim Integrated is an open-drain, active-low microprocessor supervisory circuit in a 4-pin SOT143 package, designed to monitor 3.08V power supplies with ±3% threshold accuracy over -40°C to +125°C. It asserts reset during VCC brownout or manual reset, maintains reset for ≥100ms after recovery, and draws only 4–12µA supply current. It is used in portable battery-powered equipment requiring reliable power-on reset and manual-reset capability.

For engineers reviewing the MAX6805US31D3 datasheet, MAX6805US31D3 pinout, MAX6805US31D3 application, or MAX6805US31D3 equivalent, key selection criteria include its 3.08V factory-trimmed reset threshold, 100ms minimum timeout, open-drain output compatible with bidirectional µP reset pins (e.g., Motorola 68HC11), and guaranteed operation down to VCC = 1.0V.

Technical Context

The MAX6805US31D3 implements a precision bandgap-based voltage comparator with factory-trimmed 3.08V threshold (±1.8% at +25°C, ±3% over full temperature range) and built-in immunity to fast VCC transients (e.g., rejects ≤30µs glitches at 100mV overdrive). Its internal 20kΩ MR pullup eliminates external components for manual reset.

Reset assertion is synchronized to VCC falling edge with 30µs propagation delay; deassertion follows a fixed 100ms timeout after VCC rises above threshold or MR release. The open-drain RESET output requires an external pullup and supports bidirectional reset arbitration with microcontrollers like the 68HC11.

Key Specifications

Pinout & Package

MAX6805US31D3 is housed in a 4-pin SOT143 package (outline 21-0052, land pattern 90-0183), measuring 2.9mm × 1.6mm × 1.1mm, suitable for space-constrained PCB layouts.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MAX6805US31D3, MAX6315US31D3 offers lower minimum VCC operation but sacrifices open-drain versatility, while TPS3808G33DBVR provides broader VCC support at the cost of threshold accuracy and reset timing granularity-making MAX6805US31D3 optimal for 3.08V-critical, space-constrained, and bidirectional-reset designs.

Availability

MAX6805US31D3 is available at Aetrix Electronics and suitable for portable medical sensors, industrial PLC I/O modules, handheld test equipment, and smart energy meters requiring stable component supply across automotive-grade temperature ranges and long production lifecycles.

Supply support for MAX6805US31D3 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 ICs for demanding industrial, medical, and communications applications.

The MAX680x family delivers ultra-low-power, pin-compatible µP supervisory circuits with factory-trimmed thresholds and multiple reset timeout options for space- and power-sensitive embedded systems.

FAQ

What is the factory-trimmed reset threshold voltage of the MAX6805US31D3?

The MAX6805US31D3 has a factory-trimmed reset threshold of 3.08V, specified with ±1.8% accuracy at +25°C and ±3% over the full -40°C to +125°C operating temperature range. This value is confirmed in Table 1 of the datasheet and applies exclusively to the "31" suffix variant. The MAX6805US31D3 uses this precise threshold to reliably detect brownout conditions in 3.3V systems without external calibration.

Does the MAX6805US31D3 support manual reset functionality, and how is it implemented?

Yes, the MAX6805US31D3 supports manual reset via its MR pin (Pin 3), which is active-low and features a 20kΩ internal pullup resistor. A momentary switch from MR to GND asserts reset; no external components are needed. Reset remains asserted for the full 100ms timeout period after the switch opens. This design is validated in the Applications Information section and Pin Description table of the MAX6805US31D3 datasheet.

What is the minimum supply voltage at which the MAX6805US31D3 guarantees correct reset state assertion?

The MAX6805US31D3 guarantees correct reset state assertion down to VCC = 1.0V, as explicitly stated in the General Description and Electrical Characteristics sections. This differs from the MAX6803/MAX6804 variants (guaranteed to 0.7V) and ensures reliable operation during deep brownout events where supply voltage collapses gradually. The MAX6805US31D3 maintains valid open-drain RESET output behavior within this range.

Can the MAX6805US31D3 be used with microcontrollers that have bidirectional reset pins, such as the Motorola 68HC11?

Yes, the MAX6805US31D3 is specifically designed for this use case: its open-drain RESET output (Pin 2) allows direct connection to bidirectional µP reset pins like those on the Motorola 68HC11. A single external pullup resistor enables either the MAX6805US31D3 or the µP to assert reset on the shared line. This interoperability is documented in the Applications Information section and illustrated in Figure 1 of the MAX6805US31D3 datasheet.

What is the reset timeout period of the MAX6805US31D3, and is it adjustable?

The MAX6805US31D3 has a fixed minimum reset timeout period of 100ms, as indicated by the "D3" suffix in its part number (D1 = 1ms, D2 = 20ms, D3 = 100ms). This timeout is factory-programmed and not user-adjustable. The actual timeout is typically 150ms and guaranteed between 100ms and 200ms over temperature, ensuring robust µP initialization across environmental extremes. This specification is confirmed in the Electrical Characteristics table under parameter tRP.