Analog Devices Inc./Maxim Integrated MAX6721UTYDD3+

Overview

MAX6721UTYDD3+ 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 manual reset input. It ensures reliable system reset during power-up, brownout, or software fault in battery-powered and telecom equipment.

For engineers reviewing the MAX6721UTYDD3+ datasheet, MAX6721UTYDD3+ pinout, MAX6721UTYDD3+ application, or MAX6721UTYDD3+ equivalent, key selection criteria include dual-supply monitoring accuracy (±1.5% VTH), guaranteed reset validity down to VCC = 0.8V, low 14µA supply current, and integrated watchdog with long-startup/short-normal timing modes.

Technical Context

The MAX6721UTYDD3+ implements independent voltage comparators for VCC1 and VCC2, each with factory-trimmed thresholds (4.625V and 3.075V), 20ppm/°C tempco, and 0.5% hysteresis. Reset assertion occurs when either supply falls below its threshold, and reset remains active for a minimum 210ms after both supplies recover.

It integrates a dual-mode watchdog timer: 35s minimum initial timeout after any reset event enables full system boot, followed by 1.12s minimum normal timeout requiring periodic WDI transitions. The manual reset input (MR) features internal 50kΩ pullup and 200ns MR-to-reset delay.

Key Specifications

Pinout & Package

MAX6721UTYDD3+ uses a 6-pin SOT23-6 package with exposed pad (thermal performance optimized for PCB copper area). Pin functions are validated per Maxim's official pin description table for MAX6721 series.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MAX6721UTYDD3+, MAX6722UTYDD3+ offers push-pull output for direct drive but same supervision accuracy and timing, while TPS3808G33DBVR reduces cost and power in single-rail designs at the expense of dual-supply capability and watchdog functionality.

Availability

MAX6721UTYDD3+ is available at Aetrix Electronics and suitable for telecom infrastructure, industrial PLCs, portable medical devices, and network switch line cards requiring stable component supply across extended product lifecycles.

Supply support for MAX6721UTYDD3+ 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, sensing, and interface applications, with leadership in supervisory, PMIC, and data-converter technologies.

The MAX6715–MAX6729 family delivers ultra-low-voltage, dual/triple-supply supervision in miniature SOT23 packages, targeting space-constrained, battery-sensitive, and high-reliability embedded systems.

FAQ

What is the exact reset threshold voltage for VCC1 and VCC2 on the MAX6721UTYDD3+?

The MAX6721UTYDD3+ 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 temperature range and 20ppm/°C tempco. These values are encoded in the "YD" suffix per Maxim's Reset Voltage Threshold Suffix Guide and are verified in the Electrical Characteristics table.

Does the MAX6721UTYDD3+ support watchdog functionality, and what are its timing modes?

Yes, the MAX6721UTYDD3+ includes a dual-mode watchdog timer: a 35s minimum startup timeout after any reset event (power-up, MR, or watchdog-triggered) to allow full system boot, followed by a 1.12s minimum normal timeout requiring periodic WDI transitions. This architecture prevents false resets during initialization while ensuring rapid detection of hung firmware during operation.

What is the reset output type and drive capability of the MAX6721UTYDD3+?

The MAX6721UTYDD3+ features an active-low open-drain RST output (Pin 1) requiring an external pullup resistor. It guarantees VOL ≤ 0.4V at ISINK = 3.2mA when VCC ≥ 4.5V, and exhibits ≤ 0.5µA leakage when deasserted. This configuration supports level-shifting and wired-OR reset bus architectures common in multi-IC systems.

How does the MAX6721UTYDD3+ ensure valid reset operation during severe brownout conditions?

The MAX6721UTYDD3+ guarantees correct reset output logic state down to VCC1 or VCC2 = 0.8V - significantly lower than most supervisors. This is achieved via internal biasing and comparator design that maintains functionality even as supply voltages collapse, enabling reliable recovery from deep brownouts without external support circuitry.

Can the MAX6721UTYDD3+ monitor three voltage rails, or is it limited to two?

The MAX6721UTYDD3+ is a dual-voltage supervisor and monitors only VCC1 and VCC2. It does not include RSTIN or PFI inputs - those features are present only in MAX6723–MAX6729 variants. For triple-rail monitoring, consider MAX6723UTYDD3+ (RSTIN) or MAX6728UTYDD3+ (PFI/PFO), which share the same YD thresholds and D3 timeout but add auxiliary monitoring pins.