Analog Devices Inc./Maxim Integrated MAX6721UTTGD3+

Overview

MAX6721UTTGD3+ 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, and manual reset input. It asserts active-low open-drain RST when either supply drops below threshold and maintains reset for ≥210ms after recovery - used in telecom power management and embedded systems requiring reliable brownout detection.

For engineers reviewing the MAX6721UTTGD3+ datasheet, MAX6721UTTGD3+ pinout, MAX6721UTTGD3+ application, or MAX6721UTTGD3+ equivalent, key selection criteria include dual-supply monitoring capability, 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 - critical for battery-operated and industrial control designs.

Technical Context

The MAX6721UTTGD3+ implements independent voltage comparators for VCC1 and VCC2 with factory-trimmed thresholds (4.625V and 3.075V), each referenced to internal bandgap references with 20ppm/°C tempco. Its reset logic combines ORed fault detection (VCC1/VCC2 undervoltage, MR assertion, WDI timeout) with a monostable timeout circuit ensuring ≥210ms reset pulse width.

It features a dual-mode watchdog: 35s minimum initial timeout after any reset event (power-up, MR, or watchdog-triggered), followed by 1.12s minimum normal timeout after first WDI edge detection. The open-drain RST output is referenced to VCC1 and sinks ≥1.2mA at VCC1 ≥ 2.7V, while MR includes a 50kΩ internal pullup to VCC1.

Key Specifications

Pinout & Package

Package: 6-pin SOT23-6, 1.6mm × 2.9mm footprint, 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 MAX6721UTTGD3+, MAX6326UR29D3+ omits dual-supply capability and watchdog, reducing system-level fault coverage; TPS3808G33DBVR achieves lower current but cannot supervise two rails simultaneously - MAX6721UTTGD3+ remains optimal where both VCC1 and VCC2 integrity must be verified with runtime watchdog enforcement.

Availability

MAX6721UTTGD3+ is available at Aetrix Electronics and suitable for telecom infrastructure, industrial PLCs, portable medical devices, and network switch management requiring stable component supply across extended product lifecycles.

Supply support for MAX6721UTTGD3+ 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 targeting space-constrained, multirail embedded systems requiring high reliability and minimal quiescent power.

FAQ

What is the exact reset threshold voltage for VCC1 and VCC2 on the MAX6721UTTGD3+?

The MAX6721UTTGD3+ has factory-trimmed reset thresholds of 4.625V for VCC1 and 3.075V for VCC2, with tolerances of ±125mV and ±75mV respectively. These values are fixed by the "TT" suffix per Maxim's Reset Voltage Threshold Suffix Guide and do not require external resistor programming. The MAX6721UTTGD3+ guarantees correct reset assertion when either supply falls below its respective threshold and holds reset for ≥210ms after recovery.

Does the MAX6721UTTGD3+ support watchdog functionality, and what are its timing modes?

Yes, the MAX6721UTTGD3+ includes a dual-mode watchdog timer with a 35s minimum initial timeout after any reset event (power-up, MR, or watchdog-triggered), followed by a 1.12s minimum normal timeout after the first valid WDI edge. This architecture prevents false resets during system boot while enabling rapid detection of runtime processor hangs. The WDI pin accepts TTL/CMOS-compatible signals and clears the timer on any rising or falling edge.

What package type and pin count does the MAX6721UTTGD3+ use, and is it RoHS-compliant?

The MAX6721UTTGD3+ uses a 6-pin SOT23-6 package (1.6mm × 2.9mm) with gull-wing leads and is RoHS-compliant and lead-free, indicated by the "+" suffix. It is rated for operation from -40°C to +85°C and supports reflow soldering per JEDEC J-STD-020. The pinout is fully documented in Maxim's datasheet Figure 1 and Pin Description table, with pins assigned to RST, GND, MR, VCC2, VCC1, and WDI.

How does the MAX6721UTTGD3+ ensure reliable reset behavior during low-voltage conditions?

The MAX6721UTTGD3+ guarantees valid reset output logic states down to VCC1 or VCC2 = 0.8V - significantly lower than most supervisors. This is achieved through internal biasing and comparator design that maintains reference stability and output drive capability at ultralow supply levels. As a result, the MAX6721UTTGD3+ reliably detects partial rail collapses and initiates controlled shutdown before logic corruption occurs.

Can the MAX6721UTTGD3+ monitor three voltage rails, or is it limited to two?

The MAX6721UTTGD3+ is a dual-voltage supervisor and monitors only two rails: VCC1 and VCC2. It does not include RSTIN or PFI inputs - those features are present only in MAX6723–MAX6729 variants. The "21" in MAX6721UTTGD3+ identifies it as a dual-monitor part with watchdog and manual reset, but no third-input capability. For triple-voltage monitoring, consider MAX6723UTTGD3+ or MAX6724UTTGD3+ instead.