Analog Devices Inc./Maxim Integrated MAX6821SUK+

Overview

MAX6821SUK+ from Maxim Integrated is a low-voltage microprocessor supervisory IC in SOT23-5 package, integrating voltage monitoring (preset 2.93V threshold), 140ms minimum reset timeout, 1.6s watchdog timer, manual reset input, and push-pull active-low RESET output. It ensures reliable µP initialization during power-up, brownout, and code faults in battery-powered embedded controllers.

For engineers reviewing the MAX6821SUK+ datasheet, MAX6821SUK+ pinout, MAX6821SUK+ application, or MAX6821SUK+ equivalent, this page delivers verified functional identity, exact pin roles, confirmed reset timing behavior, watchdog interaction logic, and real-world substitution guidance for industrial and automotive µP monitoring designs.

Technical Context

The MAX6821SUK+ implements a dual-stage reset generation architecture: a precision voltage comparator monitors VCC against a factory-trimmed 2.93V threshold with ±15mV tolerance over -40°C to +125°C, while an independent RC-based watchdog timer triggers reset if WDI remains static beyond 1.6s. Reset assertion is latched and held for ≥140ms after VCC recovery, MR deassertion, or watchdog timeout.

Its push-pull RESET output drives low with ≤0.4V at 3.2mA sink (VCC ≥ 4.75V) and high with ≥0.8×VCC at 800µA source, guaranteeing valid logic states down to VCC = +1.0V. The MR input features a 50kΩ internal pullup and rejects <100ns glitches, enabling direct switch-to-GND connection without external debounce.

Key Specifications

Pinout & Package

MAX6821SUK+ uses a 5-pin SOT23-5 package (JEDEC MO-178AA), 2.9mm × 1.6mm × 1.1mm body, with gull-wing leads and 0.95mm pitch. Pin 1 is marked by a dot or beveled edge.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar microprocessor supervisory applications.

Compared with MAX6821SUK+, MAX6326UT29D3+ reduces feature set to basic voltage supervision only, while TPS3808G33DBVR trades watchdog capability for 18× lower typical supply current - both require redesign of reset coordination logic and lack integrated manual reset.

Availability

MAX6821SUK+ is available at Aetrix Electronics and suitable for portable medical devices, automotive body control modules, industrial PLC I/O modules, smart energy meters, and battery-powered instrumentation requiring stable component supply across extended temperature ranges.

Supply support for MAX6821SUK+ 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 industrial, automotive, communications, and computing markets.

The MAX6821SUK+ belongs to the MAX682x family of low-voltage µP supervisors engineered for robust power-monitoring and fault-recovery in space-constrained, high-reliability embedded systems.

FAQ

What is the exact reset threshold voltage for MAX6821SUK+?

The MAX6821SUK+ has a factory-trimmed reset threshold of 2.93V, with guaranteed tolerance of ±15mV over the full -40°C to +125°C temperature range. This value is confirmed in the Threshold Suffix Guide where "S" denotes 2.93V, and electrical characteristics tables show min/typ/max values of 2.83V/2.93V/3.02V at -40°C to +125°C. The threshold is referenced to the VCC pin and remains stable due to 60ppm/°C temperature coefficient.

Does MAX6821SUK+ include a watchdog timer and manual reset input?

Yes, the MAX6821SUK+ integrates both a 1.6s watchdog timer and an active-low manual reset (MR) input. As confirmed in the Selector Guide and Pin Description, MAX6821 supports WDI and MR functions. The MR input features a 50kΩ internal pullup and 100ns glitch rejection, while the watchdog timer clears on any WDI edge and triggers reset if inactive beyond 1.6s - both functions are fully operational in MAX6821SUK+.

What is the RESET output configuration of MAX6821SUK+?

The MAX6821SUK+ provides an active-low push-pull RESET output, as specified in the Selector Guide and Pin Description table. Unlike open-drain variants (e.g., MAX6822), this configuration actively drives high and low without requiring an external pullup resistor. Electrical specs confirm VOH ≥ 0.8×VCC at 800µA source and VOL ≤ 0.4V at 3.2mA sink, enabling direct interface with standard µP reset inputs.

Can MAX6821SUK+ operate reliably below 1.8V supply voltage?

Yes, MAX6821SUK+ guarantees functional reset assertion down to VCC = +1.0V, as explicitly stated in the General Description and Electrical Characteristics. Its operating voltage range is +1.2V to +5.5V, and the reset output remains valid (logic-low during assertion, logic-high otherwise) even at 1.0V. This enables use in deep-brownout scenarios common in battery-backed systems where other supervisors fail.

How does the watchdog timer in MAX6821SUK+ interact with the manual reset input?

In MAX6821SUK+, asserting MR low clears the watchdog timer and forces immediate reset assertion for the full 140ms timeout period - identical to a watchdog timeout event. The timer restarts only after MR returns high and VCC exceeds 2.93V. This behavior is documented in the Detailed Description: "reset remains active as long as MR is low and for the timeout period after it returns high", confirming tight coupling between MR and watchdog state management.