Analog Devices Inc./Maxim Integrated MAX6721UTLTD3+

Overview

MAX6721UTLTD3+ 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, manual reset input, and open-drain active-low RST output - used to ensure reliable power-on reset and brownout protection in multivoltage embedded systems.

For engineers reviewing the MAX6721UTLTD3+ datasheet, MAX6721UTLTD3+ pinout, MAX6721UTLTD3+ application, or MAX6721UTLTD3+ equivalent, key selection factors include dual-supply threshold accuracy (±1.5% over temperature), guaranteed reset validity down to VCC = 0.8V, 14µA typical supply current at 3.6V, and integrated watchdog with 35s startup / 1.12s normal timeout modes.

Technical Context

The MAX6721UTLTD3+ implements independent voltage comparators for VCC1 and VCC2, each with factory-trimmed thresholds (4.625V and 3.075V respectively), hysteresis of 0.5%, and 20µs propagation delay. Reset assertion occurs when either supply falls below its threshold and remains asserted for a minimum 210ms after both supplies recover.

It integrates a dual-mode watchdog timer: 35s minimum initial timeout after any reset event (power-up, MR, or watchdog timeout), followed by 1.12s minimum normal timeout triggered by WDI edge transitions. The manual reset input (MR) features internal 50kΩ pullup and 200ns MR-to-RST delay.

Key Specifications

Pinout & Package

MAX6721UTLTD3+ uses a 6-pin SOT23-6 package (2.9mm × 1.6mm × 1.1mm), surface-mount, lead-free, RoHS-compliant.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MAX6722UTLTD3+, the MAX6721UTLTD3+ offers open-drain flexibility for bidirectional µP reset pins and legacy bus compatibility; versus TPS3808G33DBVR, it delivers essential dual-rail supervision and watchdog functionality required for complex embedded processors - not merely a lower-power substitute.

Availability

MAX6721UTLTD3+ is available at Aetrix Electronics and suitable for industrial PLC power management, telecom line card supervision, medical diagnostic imaging subsystems, and automotive infotainment head units requiring stable component supply, long-term lifecycle support, and guaranteed reset reliability under brownout conditions.

Supply support for MAX6721UTLTD3+ 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 industrial, communications, computing, and consumer applications.

The MAX6715–MAX6729 family was designed specifically for multivoltage embedded systems needing compact, low-power, dual- or triple-rail supervision with integrated watchdog and manual reset - targeting space-constrained, reliability-critical applications.

FAQ

What is the exact reset threshold voltage for VCC1 and VCC2 on the MAX6721UTLTD3+?

The MAX6721UTLTD3+ has factory-trimmed reset thresholds of 4.625V for VCC1 and 3.075V for VCC2, with ±1.5% tolerance over the full -40°C to +85°C operating temperature range. These values are fixed by the "LT" suffix per Maxim's Reset Voltage Threshold Suffix Guide and do not require external adjustment. The MAX6721UTLTD3+ uses these precise thresholds to detect brownout conditions on both primary and secondary supply rails independently.

Does the MAX6721UTLTD3+ support watchdog functionality, and how does it operate?

Yes, the MAX6721UTLTD3+ includes a dual-mode watchdog timer with a 35s minimum initial timeout after any reset event (power-up, MR, or prior watchdog timeout), followed by a 1.12s minimum normal timeout triggered by WDI edge transitions. The WDI pin must see a rising or falling edge within this period to prevent reset assertion. This architecture ensures safe boot completion while enabling rapid detection of software hangs during runtime - a core function of the MAX6721UTLTD3+ in mission-critical embedded systems.

What package type and pin count does the MAX6721UTLTD3+ use?

The MAX6721UTLTD3+ is packaged in a 6-pin SOT23-6 surface-mount package (2.9mm × 1.6mm × 1.1mm), RoHS-compliant and lead-free. Its pinout includes VCC1, VCC2, GND, RST (open-drain), MR (manual reset), and WDI (watchdog input). This compact footprint enables integration into space-constrained PCBs while maintaining full dual-supply supervision and watchdog capability - a defining physical characteristic of the MAX6721UTLTD3+.

Can the MAX6721UTLTD3+ monitor a third voltage rail?

No, the MAX6721UTLTD3+ is a dual-voltage supervisor and does not include an RSTIN or PFI input for monitoring a third supply. It monitors only VCC1 and VCC2. For triple-voltage supervision, Maxim offers variants such as MAX6723UTLTD3+ (with RSTIN) or MAX6728UTLTD3+ (with PFI/PFO). The MAX6721UTLTD3+ is specifically configured for two-rail systems and lacks the internal circuitry or pinout to support auxiliary voltage monitoring.

What is the minimum supply voltage at which the MAX6721UTLTD3+ guarantees correct reset output logic state?

The MAX6721UTLTD3+ guarantees valid reset output logic (correct high/low assertion) when either VCC1 or VCC2 remains ≥ 0.8V - a critical specification for robust brownout handling. Below this level, reset behavior is not guaranteed. This 0.8V specification ensures reliable operation during deep undervoltage events common in automotive and industrial environments, and is a verified design parameter of the MAX6721UTLTD3+ confirmed across temperature and process corners.