Analog Devices Inc./Maxim Integrated MAX6721UTWGD3+

Overview

MAX6721UTWGD3+ 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 open-drain 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 MAX6721UTWGD3+ datasheet, MAX6721UTWGD3+ pinout, MAX6721UTWGD3+ application, or MAX6721UTWGD3+ equivalent, key selection criteria include dual-supply monitoring range (1.8V–5.0V / 0.9V–3.3V), guaranteed reset validity down to VCC = 0.8V, low 14µA supply current, and integrated watchdog with long startup period for complex boot sequences.

Technical Context

The MAX6721UTWGD3+ integrates two 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 startup, 1.12s min normal). Its open-drain RST output asserts low when either supply drops below threshold or WDI stalls.

It features a dedicated watchdog input (WDI) with edge-triggered reset clearing, manual reset (MR) with internal 50kΩ pullup, and operates across -40°C to +85°C. Reset assertion is guaranteed while VCC1 or VCC2 ≥ 0.8V, enabling robust operation during deep brownouts.

Key Specifications

Pinout & Package

MAX6721UTWGD3+ uses a 6-pin SOT23-6 package (2.9mm × 1.6mm × 1.1mm height), 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 MAX6721UTWGD3+, MAX6722UTWGD3+ simplifies BOM by eliminating the pullup resistor but sacrifices µP bidirectional reset compatibility, while TPS3808G33DBVR reduces supply current by 82% but removes dual-supply and watchdog capabilities entirely.

Availability

MAX6721UTWGD3+ is available at Aetrix Electronics and suitable for telecom infrastructure, industrial PLCs, and portable medical devices requiring stable component supply with guaranteed long-term availability and traceable sourcing.

Supply support for MAX6721UTWGD3+ 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 connectivity applications, with leadership in supervisory, PMIC, and interface solutions.

MAX6721UTWGD3+ belongs to the MAX6715–MAX6729 family of ultra-low-voltage SOT23 µP supervisory circuits, engineered for multivoltage systems where reliability, small size, and low IQ are critical in space-constrained embedded designs.

FAQ

What is the exact reset threshold voltage for VCC1 and VCC2 on the MAX6721UTWGD3+?

The MAX6721UTWGD3+ has factory-trimmed reset thresholds of 4.625V for VCC1 (±125mV) and 3.075V for VCC2 (±75mV), as defined by the "WG" suffix per Maxim's Reset Voltage Threshold Suffix Guide. These values are measured at TA = +25°C and exhibit ±20ppm/°C tempco over -40°C to +85°C.

Does the MAX6721UTWGD3+ support manual reset, and how is it implemented?

Yes, the MAX6721UTWGD3+ includes an active-low manual reset input (MR) on Pin 3 with an internal 50kΩ pullup to VCC1. Driving MR low for ≥1µs forces reset assertion; the reset remains active for the full 210ms timeout period after MR returns high. No external components are required unless noise immunity is needed.

How does the watchdog timer function on the MAX6721UTWGD3+?

The MAX6721UTWGD3+ watchdog uses a dual-mode architecture: after any reset event, it enters a 35s minimum startup period to allow full system boot, then switches to a 1.12s minimum normal timeout. A rising or falling edge on WDI (Pin 6) clears the timer; failure to update within the active mode timeout asserts RST for 210ms.

Is the MAX6721UTWGD3+ compatible with bidirectional microprocessor reset pins?

Yes - the MAX6721UTWGD3+ provides an open-drain RST output (Pin 1), which is electrically compatible with bidirectional µP reset I/O ports. To avoid contention, connect RST to the µP reset pin through a 4.7kΩ series resistor, as recommended in Maxim's application guidance for such interfaces.

What is the minimum operating voltage guarantee for valid reset output on the MAX6721UTWGD3+?

The MAX6721UTWGD3+ guarantees correct reset output logic state down to VCC1 or VCC2 = 0.8V. Below this, reset behavior is not specified. For applications requiring valid reset down to 0V, a 100kΩ pull-down resistor from RST to GND is recommended - though this applies only to push-pull variants, not the open-drain MAX6721UTWGD3+.