Analog Devices Inc./Maxim Integrated MAX6721UTTGD3

Overview

MAX6721UTTGD3 from Maxim Integrated is a dual-voltage microprocessor supervisory IC in 6-pin SOT23 package, monitoring VCC1 (primary supply) and VCC2 (secondary supply) with factory-trimmed reset thresholds of 4.625V and 3.075V respectively, 210ms minimum reset timeout, watchdog timer with 35s startup and 1.12s normal mode, and push-pull active-low RST output. It ensures reliable system reset during power-up, brownout, or software fault in embedded controllers.

For engineers reviewing the MAX6721UTTGD3 datasheet, MAX6721UTTGD3 pinout, MAX6721UTTGD3 application, or MAX6721UTTGD3 equivalent, key selection criteria include dual-supply threshold accuracy (±1.5% over -40°C to +125°C), guaranteed reset validity down to VCC1/VCC2 = 0.8V, low 14µA typical supply current at 3.6V, and integrated watchdog disable via open WDI pin.

Technical Context

The MAX6721UTTGD3 implements independent dual-supply monitoring using precision bandgap-referenced comparators for VCC1 and VCC2, with internal hysteresis (0.5%) and 20ppm/°C tempco. Its watchdog timer operates in two phases: a 35s minimum startup period after any reset event, followed by a 1.12s minimum normal timeout triggered by WDI edge transitions.

Reset assertion occurs when either VCC1 falls below 4.625V or VCC2 falls below 3.075V, or when MR is pulled low; reset remains asserted for ≥210ms after all monitored supplies exceed thresholds. The push-pull RST output is referenced to VCC1 and sinks up to 3.2mA at VCC1 ≥ 4.5V with VOL ≤ 0.4V.

Key Specifications

Pinout & Package

Package: 6-pin SOT23, 1.6mm × 2.9mm × 1.1mm body, lead-free/RoHS-compliant.

Key Features

Applications

Equivalent & Alternatives

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

Compared with TPS3808G33DBVR and ADM6710LAKSZ-REEL7, the MAX6721UTTGD3 uniquely delivers factory-trimmed dual-threshold supervision (4.625V/3.075V), integrated two-phase watchdog, and guaranteed operation down to 0.8V - making it optimal for safety-critical dual-rail systems requiring both precision and fault resilience.

Availability

MAX6721UTTGD3 is available at Aetrix Electronics and suitable for industrial PLC controllers, automotive ADAS ECUs, medical infusion pumps, and telecom base station power supplies requiring stable component supply across extended temperature ranges and long 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 and mixed-signal ICs for demanding industrial, automotive, and communications applications.

The MAX6715A–MAX6729A family delivers ultra-low-voltage supervisory circuits optimized for dual/triple supply monitoring in space-constrained, high-reliability embedded systems operating from -40°C to +125°C.

FAQ

What is the exact reset timeout period for MAX6721UTTGD3?

The MAX6721UTTGD3 has a minimum reset timeout period of 210ms, as defined by the 'D3' suffix in its part number. This timeout begins when all monitored supplies (VCC1 and VCC2) rise above their respective thresholds and ends when the RST output deasserts. The actual timeout is typically 210ms at +25°C and varies within ±20% over the full -40°C to +125°C operating range, ensuring robust timing margin for microprocessor boot sequences.

Does MAX6721UTTGD3 support monitoring a third voltage rail?

No, the MAX6721UTTGD3 does not support a third voltage rail. It is a dual-supply supervisor monitoring only VCC1 and VCC2. Models such as MAX6723A–MAX6727A include the RSTIN pin for externally adjustable third-rail monitoring, but MAX6721UTTGD3 lacks this pin and associated circuitry. Its pinout is fixed to six terminals: VCC1, VCC2, GND, RST, MR, and WDI - with no provision for auxiliary voltage input.

How is the watchdog function enabled or disabled on MAX6721UTTGD3?

The watchdog function on MAX6721UTTGD3 is disabled by leaving the WDI pin unconnected. Internally, an unconnected-state detector uses a 200nA current source to sense the floating condition. To enable the watchdog, drive WDI with clean CMOS-level edges (rising or falling) at intervals shorter than 1.12s in normal mode. Connecting WDI to a static high or low level will trigger reset after the timeout period. Do not connect WDI to sources exceeding 50nA leakage, as this may prevent proper disable detection.

What are the absolute maximum ratings for VCC1 and VCC2 on MAX6721UTTGD3?

The absolute maximum rating for both VCC1 and VCC2 on MAX6721UTTGD3 is +6V, with a minimum of -0.3V relative to GND. Operation beyond these limits risks permanent damage. The device is specified to operate continuously from 0.8V to 5.5V per supply, and reset functionality is guaranteed down to 0.8V. Exceeding 5.5V during normal operation violates the recommended operating conditions and may cause incorrect threshold comparisons or output behavior, even if within absolute maximum limits.

Can MAX6721UTTGD3 be used with a bidirectional µP reset pin?

Yes, MAX6721UTTGD3 can interface with bidirectional µP reset pins, but requires a 4.7kΩ series resistor between its push-pull RST output and the µP's reset I/O port to prevent logic contention. This resistor isolates the supervisor's strong push-pull driver from the µP's internal weak pullup/pulldown, allowing safe bidirectional communication. Direct connection without the resistor may cause excessive current flow or undefined reset states during µP-controlled reset assertion, especially in systems where the µP drives reset low during self-test or recovery routines.