Analog Devices Inc./Maxim Integrated MAX6721UTVDD3+T

Overview

MAX6721UTVDD3+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 telecom and industrial controllers.

For engineers reviewing the MAX6721UTVDD3+T datasheet, MAX6721UTVDD3+T pinout, MAX6721UTVDD3+T application, or MAX6721UTVDD3+T equivalent, key selection criteria include dual-supply monitoring range (1.8–5.0V / 0.9–3.3V), 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 MAX6721UTVDD3+T implements independent voltage comparators for VCC1 and VCC2, each with factory-trimmed thresholds (4.625V and 3.075V), hysteresis of 0.5%, and tempco of 20ppm/°C. Reset assertion occurs when either supply falls below its threshold, and reset remains asserted for a minimum 210ms after both supplies recover.

Its dual-mode watchdog uses a 35s minimum initial timeout after any reset event-enabling full system initialization-then switches to 1.12s minimum normal timeout upon first WDI edge detection. The open-drain RST output requires external pullup and is guaranteed functional with VCC1 or VCC2 ≥ 0.8V.

Key Specifications

Pinout & Package

Package: 6-pin SOT23-6, surface-mount, lead-free (+T suffix), footprint compatible with JEDEC MO-178AB.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MAX6722UTVDD3+T, the MAX6721UTVDD3+T provides open-drain flexibility for bus arbitration but requires external pullup; versus TPS3808G33DBVR, it delivers full dual-supply supervision and watchdog-reducing BOM count and improving system-level reliability.

Availability

MAX6721UTVDD3+T is available at Aetrix Electronics and suitable for telecom power management, industrial PLC controllers, portable medical monitors, and network switch ASIC power sequencing requiring stable component supply and long-term lifecycle support.

Supply support for MAX6721UTVDD3+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, mixed-signal, and power management ICs for demanding industrial, automotive, and communications applications.

The MAX6715–MAX6729 family delivers ultra-low-voltage, dual/triple-supply supervisory circuits in miniature SOT23 packages-targeting space-constrained, battery-operated, and high-reliability embedded systems requiring guaranteed reset behavior across wide voltage and temperature ranges.

FAQ

What is the exact reset threshold voltage for VCC1 and VCC2 on the MAX6721UTVDD3+T?

The MAX6721UTVDD3+T has factory-trimmed reset thresholds of 4.625V for VCC1 (±125mV) and 3.075V for VCC2 (±75mV), as indicated by the "VD" suffix per Maxim's Reset Voltage Threshold Suffix Guide. These values are measured under standard conditions (TA = +25°C) and maintain ±0.5% hysteresis and 20ppm/°C tempco across the full -40°C to +85°C operating range. The MAX6721UTVDD3+T guarantees correct reset logic state as long as either VCC1 or VCC2 remains above 0.8V.

Does the MAX6721UTVDD3+T include a watchdog timer, and how does it operate?

Yes, the MAX6721UTVDD3+T integrates a dual-mode watchdog timer with a 35s minimum startup timeout after any reset event (power-up, brownout, MR, or watchdog timeout), followed by a 1.12s minimum normal timeout once the first valid edge is detected on the WDI pin. This architecture prevents false resets during lengthy boot sequences while ensuring rapid fault detection during runtime. The MAX6721UTVDD3+T watchdog clears on any WDI transition and asserts RST for the full 210ms reset timeout period upon timeout.

What package type and pin count does the MAX6721UTVDD3+T use?

The MAX6721UTVDD3+T is packaged in a 6-pin SOT23-6 (also referenced as SOT-23-6) surface-mount package with lead-free finish (+T suffix), compliant with JEDEC MO-178AB dimensions. Its pinout includes VCC1, VCC2, GND, RST (open-drain), MR, and WDI-no RST2 or PFI/PFO pins, confirming its dual-supply, watchdog-enabled, non-power-fail variant within the MAX6721–MAX6729 family.

Can the MAX6721UTVDD3+T monitor a third voltage rail?

No, the MAX6721UTVDD3+T is a dual-voltage supervisor and does not support a third monitored rail. It lacks the RSTIN input required for externally adjustable auxiliary voltage monitoring-this feature is present only in MAX6719/MAX6720/MAX6723–MAX6727 variants. The MAX6721UTVDD3+T monitors only VCC1 and VCC2, with fixed factory-trimmed thresholds. For triple-voltage supervision, consider MAX6723UTVDD3+T or MAX6724UTVDD3+T instead.

What is the reset output type and drive capability of the MAX6721UTVDD3+T?

The MAX6721UTVDD3+T features an active-low, open-drain RST output requiring an external pullup resistor. It is guaranteed to sink ≥1.2mA at VCC ≥ 2.7V (VOL ≤ 0.3V) and exhibits ≤0.5µA leakage when deasserted. The output remains valid with VCC1 or VCC2 as low as 0.8V, enabling robust reset signaling during deep brownout conditions. This open-drain configuration supports wired-OR reset busses and level translation-unlike push-pull variants such as MAX6722UTVDD3+T.