Analog Devices Inc./Maxim Integrated MAX6721UTSVD3+T

Overview

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

For engineers reviewing the MAX6721UTSVD3+T datasheet, MAX6721UTSVD3+T pinout, MAX6721UTSVD3+T application, or MAX6721UTSVD3+T equivalent, key selection criteria include dual-supply monitoring accuracy (±1.5% VTH), guaranteed reset validity down to VCC = 0.8V, low 14µA supply current at 3.6V, and integrated watchdog with long startup period for complex boot sequences.

Technical Context

The MAX6721UTSVD3+T implements dual independent voltage comparators with factory-trimmed thresholds (VTH1 = 4.625V, VTH2 = 3.075V), a 210ms minimum reset timeout timer, and a dual-mode watchdog (35s min initial, 1.12s min normal). Its reset logic asserts RST low when either supply drops below threshold or WDI stalls, holding reset for full timeout after recovery.

It features an open-drain RST output referenced to VCC1, internal 50kΩ MR pullup, and watchdog input compatible with TTL/CMOS logic levels. The device operates across -40°C to +85°C and guarantees valid reset state with VCC1 or VCC2 ≥ 0.8V - critical for low-voltage brownout detection in portable systems.

Key Specifications

Pinout & Package

MAX6721UTSVD3+T is housed in a 6-pin SOT23-6 package (1.6mm × 2.9mm × 1.1mm), surface-mount, lead-free (+T suffix), with thermal pad not connected.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MAX6722UTSVD3+T, the MAX6721UTSVD3+T offers safer interoperability with bidirectional µP reset I/O but requires a pullup resistor; versus TPS3808G33DBVR, it delivers full dual-rail supervision and watchdog capability at higher current draw-justified in complex embedded systems.

Availability

MAX6721UTSVD3+T is available at Aetrix Electronics and suitable for telecom infrastructure, industrial PLCs, portable medical devices, and battery-powered gateways requiring stable component supply with guaranteed long-term availability.

Supply support for MAX6721UTSVD3+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 and mixed-signal ICs for power, sensing, and timing applications, with emphasis on high-reliability industrial and communications systems.

The MAX6715–MAX6729 family delivers ultra-low-voltage dual/triple supervisory circuits optimized for multivoltage embedded systems where simultaneous rail monitoring, watchdog safety, and minimal quiescent current are critical.

FAQ

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

The MAX6721UTSVD3+T has factory-trimmed reset thresholds of 4.625V for VCC1 and 3.075V for VCC2, with ±1.5% tolerance over temperature. These values are encoded in the "SV" suffix per Maxim's Reset Voltage Threshold Suffix Guide and verified in the Electrical Characteristics table (page 2 of datasheet).

Does the MAX6721UTSVD3+T support manual reset, and how is it implemented?

Yes, the MAX6721UTSVD3+T includes an active-low manual reset input (MR) on Pin 3, featuring an internal 50kΩ pullup to VCC1. A logic-low pulse ≥1µs on MR forces RST assertion for the full 210ms timeout period, enabling hardware-initiated recovery without firmware involvement.

What watchdog behavior does the MAX6721UTSVD3+T provide, and how is it configured?

The MAX6721UTSVD3+T implements a dual-mode watchdog: 35s minimum startup period after reset (allowing full system boot), followed by 1.12s minimum normal timeout. No configuration is required-WDI (Pin 6) is edge-triggered; any rising or falling edge resets the timer, and stall beyond timeout asserts RST.

Is the MAX6721UTSVD3+T compatible with bidirectional microprocessor reset pins?

Yes-the MAX6721UTSVD3+T uses an open-drain RST output (Pin 1), which is inherently compatible with bidirectional µP reset I/O. An external pullup resistor to VCC1 is required, and no contention occurs during µP-driven reset assertion, unlike push-pull alternatives.

What is the minimum operating voltage guarantee for reset validity on the MAX6721UTSVD3+T?

The MAX6721UTSVD3+T guarantees correct reset output logic state (asserted or deasserted) as long as either VCC1 or VCC2 remains ≥0.8V. This ensures reliable brownout detection far below nominal rail voltages-critical for graceful shutdown in battery-depleted conditions.