Analog Devices Inc./Maxim Integrated MAX806RESA+

Overview

MAX806RESA+ from Maxim Integrated is a 3.0V/3.3V microprocessor supervisory circuit with active-high open-drain RESET output, 2.625V reset threshold (R-suffix), 200ms reset timeout, watchdog timer (1.6s), and battery-backup switchover. It monitors VCC, asserts reset during power-up/brownout/watchdog timeout, and switches VOUT to VBATT when VCC falls below 2.40V - used in battery-powered embedded controllers requiring reliable power sequencing and RAM backup.

For engineers reviewing the MAX806RESA+ datasheet, MAX806RESA+ pinout, MAX806RESA+ application, or MAX806RESA+ equivalent, this page delivers verified specifications, validated pin functions, confirmed use cases in portable instrumentation and critical µP monitoring, and two technically documented alternative parts with explicit tolerance and functional distinctions.

Technical Context

The MAX806RESA+ integrates a precision reset comparator with ±2% threshold accuracy (2.625V rising/falling), a 1.6s watchdog timer that clears on WDI edge transitions and cannot be disabled, and a dual-path power-switching architecture: VCC-to-VOUT via 3Ω PMOS switch and VBATT-to-VOUT via 140Ω switch activated at VSW = 2.40V. Its PFI input features 1.237V threshold with 10mV hysteresis for independent power-fail detection.

It operates across –40°C to +85°C (E-grade), draws only 40µA from VCC (typ) and 0.4–1µA from VBATT, guarantees RESET assertion down to VCC = 1V, and supports manual reset via MR with internal 70µA pull-up. The active-high RESET output is open-drain, requiring external pull-up, and shares pin 7 with the MAX804/MAX805 family - distinct from the active-low RESET of MAX690/MAX704/MAX802.

Key Specifications

Pinout & Package

MAX806RESA+ is housed in an 8-pin SOIC package (SO) with gull-wing leads, RoHS-compliant (indicated by '+' suffix), 1.27mm pitch, and JEDEC MS-012AC outline.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MAX806RESA+, MAX804RESA+ offers identical supervision accuracy but inverted reset polarity, while MAX706RESA+ omits watchdog and battery switching - making MAX806RESA+ the sole choice for designs requiring both RAM retention and µP fault recovery.

Availability

MAX806RESA+ is available at Aetrix Electronics and suitable for battery-powered computers and controllers, intelligent instruments, and critical µP power monitoring requiring stable component supply, long-term industrial temperature support, and RoHS-compliant packaging.

Supply support for MAX806RESA+ 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, and communications applications, emphasizing reliability and integration.

The MAX806RESA+ belongs to the MAX80x family of 3.0V/3.3V µP supervisory circuits, engineered specifically for systems needing coordinated reset generation, watchdog monitoring, and seamless battery-backed RAM retention in space-constrained portable equipment.

FAQ

What is the reset threshold voltage of the MAX806RESA+ and how is it specified?

The MAX806RESA+ has a nominal reset threshold of 2.625V, with ±2% tolerance over temperature and supply variations. This value applies to both VCC rising and falling edges, and is optimized for 3.0V ±10% power systems. The tighter tolerance distinguishes it from earlier families like MAX690 (±4%), ensuring more precise brownout detection in sensitive embedded applications. The R-suffix explicitly denotes this 2.625V variant.

Does the MAX806RESA+ include a watchdog timer, and how does it operate?

Yes, the MAX806RESA+ includes a non-disableable watchdog timer with a nominal timeout of 1.6 seconds. It is cleared by any edge (rising or falling) on the WDI pin and triggers a reset if WDI remains static beyond that period. Unlike some older supervisors, the watchdog cannot be disabled - ensuring continuous µP health monitoring. This behavior is confirmed in the Detailed Description section of the datasheet and applies identically across all MAX806 variants.

How does the battery switchover function work on the MAX806RESA+?

The MAX806RESA+ switches VOUT from VCC to VBATT when VCC falls below the battery switchover threshold VSW = 2.40V (2.30–2.50V), provided VBATT exceeds VCC. This 140Ω internal switch preserves CMOS RAM data during brownout. Switchover back to VCC occurs only after VCC rises above the reset threshold (2.625V), not VSW - preventing premature reconnection during marginal recovery. The design allows VBATT to exceed VCC (e.g., 3.6V Li-cell), a key requirement for long-life backup.

What is the function of the PFI and PFO pins on the MAX806RESA+?

The PFI (Power-Fail Input) pin accepts an external voltage - typically from a resistor divider - and compares it to a 1.237V internal reference. When PFI falls below this threshold, the open-drain PFO (Power-Fail Output) pulls low. This enables independent monitoring of auxiliary rails (e.g., 5V or analog supplies). PFO can also be connected to MR on compatible devices like MAX704/MAX806 to generate a reset on auxiliary supply failure - a capability confirmed in Figure 5b of the datasheet.

Is the RESET output of the MAX806RESA+ active-high or active-low, and what are its drive characteristics?

The RESET output of the MAX806RESA+ is active-high and open-drain, located on pin 7. It requires an external pull-up resistor to VCC. When asserted, it pulls high; when deasserted, it enters high-impedance state. It sources up to 50µA at VOH = VCC – 0.05V and sinks up to 1.2mA at VOL = 0.3V. This differs from the active-low RESET of MAX690/MAX704/MAX802 and matches the MAX804/MAX805 family - a critical layout consideration for pin-compatible designs.