Analog Devices Inc./Maxim Integrated MAX6731UTWD3+T

Overview

MAX6731UTWD3+T from Maxim Integrated is a single-voltage microprocessor supervisor IC with active-low push-pull reset output, manual reset input, and independent watchdog timer featuring 1.12s normal timeout and 35s startup delay. It monitors VCC1 at factory-set +3.075V (suffix 'W'), guarantees valid reset down to VCC1 = +0.8V, and draws only 14µA typical supply current - used in embedded systems requiring reliable power-on and brownout reset control.

For engineers reviewing the MAX6731UTWD3+T datasheet, MAX6731UTWD3+T pinout, MAX6731UTWD3+T application, or MAX6731UTWD3+T equivalent, key selection considerations include its fixed +3.075V VCC1 threshold, D3 reset timeout (140–280ms), push-pull RST/WDO outputs, SOT23-6 package, and compatibility with manual reset and watchdog-driven system recovery in space-constrained industrial and telecom designs.

Technical Context

The MAX6731UTWD3+T implements a dual-mode watchdog timer: a 35s minimum startup delay after reset enables full system initialization before watchdog monitoring begins, followed by a 1.12s minimum normal timeout period for rapid fault detection during runtime. Its reset logic asserts RST low when VCC1 falls below +3.075V (±125mV), MR is pulled low, or WDI stalls - with hysteresis (0.5%) and immunity to sub-100ns VCC transients.

It features a dedicated push-pull RST output (VOH ≥ 0.8×VCC1, VOL ≤ 0.3V at ISINK = 1.2mA) and push-pull WDO output, eliminating external pullups. The internal 50kΩ MR pullup resistor supports direct switch-to-GND interfacing without debounce circuitry, and RST remains asserted for the full D3 timeout (140–280ms) after all fault conditions clear.

Key Specifications

Pinout & Package

SOT23-6 package (U6+1 outline, land pattern 90-0175), 2.9mm × 1.6mm × 1.1mm body, gull-wing leads, RoHS-compliant lead(Pb)-free finish (+T suffix).

Key Features

Applications

Equivalent & Alternatives

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

Compared with MAX6731UTWD3+T, MAX6316US31D3+T offers lower cost but sacrifices manual reset and output drive strength, while TPS3808G33DBVR achieves lower current draw but removes critical watchdog and MR capabilities - making MAX6731UTWD3+T the optimal choice for integrated, self-recovering embedded systems requiring both reset and watchdog in one SOT23-6 package.

Availability

MAX6731UTWD3+T is available at Aetrix Electronics and suitable for industrial PLC controllers, telecom line cards, medical handheld diagnostics, network router management modules, and battery-operated embedded systems requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for MAX6731UTWD3+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 markets.

The MAX6730–MAX6735 family delivers highly integrated microprocessor supervisors with factory-configurable thresholds, dual-mode watchdogs, and flexible reset outputs - engineered specifically for reliability-critical embedded systems demanding robust power sequencing and fault recovery.

FAQ

What is the exact VCC1 reset threshold voltage for MAX6731UTWD3+T?

The MAX6731UTWD3+T has a factory-set VCC1 reset threshold of +3.075V (±125mV), corresponding to the 'W' suffix in its ordering code. This value is guaranteed over the full -40°C to +85°C operating range with 20ppm/°C tempco and 0.5% hysteresis, ensuring precise brownout detection for +3.3V systems. The threshold is internally trimmed and does not require external components.

Does MAX6731UTWD3+T support manual reset, and how is it implemented?

Yes, MAX6731UTWD3+T includes an active-low manual reset input (MR) with an internal 50kΩ pullup resistor to VCC1. Driving MR to GND for ≥1µs forces RST low for the full D3 timeout period (140–280ms). The MR pin accepts TTL/CMOS logic levels and supports direct connection to a momentary switch without external debounce circuitry, simplifying front-panel or test-point reset implementation.

What are the watchdog timeout periods supported by MAX6731UTWD3+T?

MAX6731UTWD3+T features a dual-mode watchdog timer: a minimum 35s startup delay after any reset event (power-up, brownout, or MR assertion), followed by a minimum 1.12s normal timeout period. The watchdog clears on any rising or falling edge at WDI and asserts WDO low if no edge occurs within the active timeout window - enabling safe boot initialization and rapid runtime fault detection.

Is MAX6731UTWD3+T compatible with bidirectional microprocessor reset pins?

Yes, but with caution: MAX6731UTWD3+T's push-pull RST output may cause logic contention when connected directly to a bidirectional µP reset I/O. To prevent this, insert a 10kΩ series resistor between RST and the µP reset pin. This limits current during potential bus conflicts while preserving signal integrity and reset timing - a recommended practice documented in the MAX6730–MAX6735 application note.

What package type and footprint does MAX6731UTWD3+T use?

MAX6731UTWD3+T uses the SOT23-6 package (outline U6+1, land pattern 90-0175), measuring 2.9mm × 1.6mm × 1.1mm with gull-wing leads. It is RoHS-compliant and lead(Pb)-free (+T suffix), with thermal characteristics θJA = 230°C/W and θJC = 76°C/W. This compact footprint supports high-density PCB layouts in space-constrained industrial and telecom applications.