Analog Devices Inc./Maxim Integrated MAX6721UTSVD3

Overview

MAX6721UTSVD3 from Maxim Integrated is a dual-voltage microprocessor supervisory circuit in 6-pin SOT23 package, monitoring VCC1 (4.625V threshold) and VCC2 (3.075V threshold) with 210ms reset timeout, watchdog timer (35s startup / 1.12s normal), and push-pull active-low RST output. It ensures reliable system reset during power-up, brownout, or software fault in battery-powered telecom and industrial controllers.

For engineers reviewing the MAX6721UTSVD3 datasheet, MAX6721UTSVD3 pinout, MAX6721UTSVD3 application, or MAX6721UTSVD3 equivalent, key selection criteria include dual-supply threshold accuracy (±1.5% over -40°C to +125°C), guaranteed reset validity down to VCC1/VCC2 = 0.8V, low 14µA supply current at 3.6V, and integrated watchdog with long startup period for complex boot sequences.

Technical Context

The MAX6721UTSVD3 implements independent voltage comparators for VCC1 and VCC2, each with factory-trimmed thresholds (4.625V and 3.075V respectively), hysteresis of 0.5%, and temperature coefficient of 20ppm/°C. Its dual-mode watchdog uses a 35s minimum startup delay after any reset event, then transitions to 1.12s minimum normal timeout upon first WDI edge detection.

This device integrates push-pull RST output referenced to VCC1, manual-reset input (MR) with 50kΩ internal pullup, and watchdog input (WDI) with 200nA unconnected-state detection. Reset assertion occurs on VCC1/VCC2 undervoltage, MR low, or WDI timeout, and remains asserted for exactly 210ms (min) after all conditions clear.

Key Specifications

Pinout & Package

MAX6721UTSVD3 is housed in a 6-pin SOT23 package (2.9mm × 1.6mm × 1.1mm), RoHS-compliant, with thermal pad option not included. Pin 1 is marked by dot; pin numbering follows standard SOT23 convention (counterclockwise from mark).

Key Features

Applications

Equivalent & Alternatives

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

Compared with MAX6720UTSVD3, the MAX6721UTSVD3 adds critical watchdog functionality for runtime software integrity; compared with TPS3808G33DBVR, it provides true dual-rail supervision in one package, eliminating layout complexity and inter-IC timing skew.

Availability

MAX6721UTSVD3 is available at Aetrix Electronics and suitable for telecom line cards, industrial PLCs, battery-powered gateways, and automotive infotainment systems requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for MAX6721UTSVD3 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) is a semiconductor company specializing in high-performance analog, mixed-signal, and power-management ICs for demanding industrial, automotive, and communications applications.

The MAX6715A–MAX6729A family was designed specifically for ultra-low-voltage, multi-rail microprocessor supervision in space-constrained, thermally aggressive environments where reliability and precision thresholding are critical.

FAQ

What is the exact reset threshold voltage for VCC1 and VCC2 on the MAX6721UTSVD3?

The MAX6721UTSVD3 has factory-trimmed reset thresholds of 4.625V for VCC1 and 3.075V for VCC2, with ±1.5% tolerance over -40°C to +125°C. These values are fixed by the part number suffix 'D3' per Maxim's Reset Voltage Threshold Suffix Guide and do not require external resistor programming. The MAX6721UTSVD3 guarantees these thresholds remain stable with 20ppm/°C tempco.

Does the MAX6721UTSVD3 support watchdog functionality, and what are its timing modes?

Yes, the MAX6721UTSVD3 includes a dual-mode watchdog timer: a 35-second minimum startup period after any reset event (power-up, MR, or watchdog timeout), followed by a 1.12-second minimum normal timeout period triggered by the first valid WDI edge. This architecture prevents false resets during boot while enabling rapid detection of runtime software hangs. The MAX6721UTSVD3 watchdog is disabled when WDI is left floating (200nA detection current).

What package type and pin count does the MAX6721UTSVD3 use, and is it RoHS-compliant?

The MAX6721UTSVD3 is supplied in a 6-pin SOT23 package (2.9mm × 1.6mm × 1.1mm) with lead-free/RoHS-compliant finish (denoted by '+' in ordering code). It features standard SOT23 pinout: Pin 1=RST, Pin 2=GND, Pin 3=MR, Pin 4=VCC2, Pin 5=VCC1, Pin 6=WDI. The MAX6721UTSVD3 thermal performance is rated for 696mW continuous dissipation at +70°C ambient.

How does the MAX6721UTSVD3 ensure valid reset output during deep brownout conditions?

The MAX6721UTSVD3 guarantees correct reset logic state (RST low when asserted) even when VCC1 or VCC2 drops to 0.8V - significantly below typical reset thresholds. This is achieved through proprietary internal biasing and comparator design. Unlike many supervisors that fail unpredictably below 1.2V, the MAX6721UTSVD3 maintains deterministic behavior, enabling safe recovery from severe brownouts. This specification is explicitly tested and guaranteed across temperature.

Can the MAX6721UTSVD3 monitor a third voltage rail, and if not, what are the alternatives?

No, the MAX6721UTSVD3 is a dual-supply supervisor and does not include the RSTIN input required for auxiliary voltage monitoring. For triple-voltage supervision, consider the MAX6723UTSVD3 (same thresholds and timeout) which adds the RSTIN pin with 626mV internal reference. That device allows external resistor-divider programming to monitor a third rail down to 0.62V. The MAX6721UTSVD3 pinout and function set are strictly limited to VCC1, VCC2, MR, WDI, GND, and RST.