Analog Devices Inc./Maxim Integrated MAX6721UTSDD3

Overview

The MAX6721UTSDD3 from Maxim Integrated is a dual-voltage microprocessor supervisory circuit in 6-pin SOT23 package, monitoring primary (VCC1) and secondary (VCC2) supplies with factory-trimmed reset thresholds of 4.625V (VTH1) and 3.075V (VTH2), 210ms minimum reset timeout, and integrated watchdog timer with 35s startup/1.12s normal mode. It asserts active-low push-pull RST when either supply drops below threshold and maintains reset for the full timeout period-used in telecom power management and industrial embedded controllers requiring reliable brownout detection.

For engineers reviewing the MAX6721UTSDD3 datasheet, MAX6721UTSDD3 pinout, MAX6721UTSDD3 application, or MAX6721UTSDD3 equivalent, key selection criteria include its dual-supply monitoring capability down to 0.8V VCC operation, guaranteed reset validity across -40°C to +125°C, low 14µA typical supply current, and watchdog disable-by-open WDI feature for flexible system initialization control.

Technical Context

This device implements dual independent voltage comparators with hysteresis (0.5% of VTH), a precision internal 626.5mV reference for RSTIN/PFI inputs, and a dual-mode watchdog timer that transitions from 35s min startup period to 1.12s min normal timeout after first WDI edge. Reset assertion is synchronized to VCC1/VCC2 crossing thresholds with 20µs propagation delay.

The supervisor guarantees valid reset logic state even when VCC1 or VCC2 falls as low as 0.8V, uses internal 50kΩ MR pullup, and supports both push-pull and open-drain RST/RST2 outputs referenced to VCC1 and VCC2 respectively-enabling robust reset coordination across mixed-voltage domains without external level-shifting.

Key Specifications

Pinout & Package

MAX6721UTSDD3 is housed in a 6-pin SOT23 package (2.9mm × 1.6mm × 1.1mm), surface-mount, RoHS-compliant, with thermal pad option not included.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar dual-voltage supervisory applications.

Compared with MAX6721UTSDD3, MAX6720UTSDD3 removes watchdog capability while retaining identical dual-threshold supervision, whereas TPS3808G33DBVR reduces integration by supporting only one supply rail and lacks VCC2 monitoring-making MAX6721UTSDD3 uniquely suited for compact, thermally constrained dual-rail systems needing both voltage supervision and runtime software assurance.

Availability

MAX6721UTSDD3 is available at Aetrix Electronics and suitable for telecom infrastructure, industrial PLCs, and automotive infotainment systems requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for MAX6721UTSDD3 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 and mixed-signal ICs for power management, sensing, and interface applications across industrial, automotive, and communications markets.

The MAX6715A–MAX6729A family delivers ultra-low-voltage, dual/triple-supply supervisory circuits optimized for space-constrained embedded systems demanding high reliability, wide temperature operation, and flexible reset timing.

FAQ

What is the exact reset threshold voltage for VCC1 and VCC2 on the MAX6721UTSDD3?

The MAX6721UTSDD3 has factory-trimmed reset thresholds of 4.625V for VCC1 (with ±125mV tolerance) and 3.075V for VCC2 (with ±75mV tolerance), as defined by the 'TD' suffix in its part number per Maxim's Reset Voltage Threshold Suffix Guide. These values are guaranteed over the full -40°C to +125°C operating range and include 0.5% hysteresis to prevent chatter near trip points.

Does the MAX6721UTSDD3 support watchdog functionality, and how is it configured?

Yes, the MAX6721UTSDD3 includes a dual-mode watchdog timer with a 35s minimum startup period and 1.12s minimum normal timeout. It is enabled by driving the WDI pin with periodic edges; leaving WDI unconnected disables the watchdog entirely. The internal 200nA WDI unconnected-state detector ensures reliable disable behavior without external pull resistors.

What package type and pin count does the MAX6721UTSDD3 use?

The MAX6721UTSDD3 is supplied in a 6-pin SOT23 package (2.9mm × 1.6mm × 1.1mm footprint), RoHS-compliant and tape-and-reel packaged. Pinout is fixed per Maxim's ordering guide: Pin 1 = RST, Pin 2 = GND, Pin 3 = MR, Pin 4 = VCC2, Pin 5 = VCC1, Pin 6 = WDI.

Can the MAX6721UTSDD3 monitor a third voltage rail, and if so, how?

No, the MAX6721UTSDD3 is a dual-supply supervisor and does not include the RSTIN input required for adjustable third-rail monitoring. That function is available only on variants like MAX6723A–MAX6727A. For triple-voltage supervision, consider MAX6723UTSDD3 (same thresholds/timing but adds RSTIN pin) or redesign with external resistor divider into PFI if power-fail alert suffices.

What is the minimum supply voltage at which the MAX6721UTSDD3 guarantees valid reset output logic?

The MAX6721UTSDD3 guarantees correct reset output logic state (RST asserted low or deasserted high) as long as either VCC1 or VCC2 remains ≥0.8V. This specification ensures fail-safe operation during deep brownout conditions common in automotive and industrial power systems, unlike many supervisors that require ≥1.2V or higher for valid reset assertion.