Analog Devices Inc./Maxim Integrated MAX802TESA+

Overview

MAX802TESA+ from Maxim Integrated is a 3.3V microprocessor supervisory circuit with precision reset threshold (3.075V ±2%), 200ms reset timeout, integrated watchdog timer (1.6s), battery-backup switchover, and power-fail detection. It monitors VCC supply integrity and manages CMOS RAM backup via VBATT in embedded controllers and portable equipment.

For engineers reviewing the MAX802TESA+ datasheet, MAX802TESA+ pinout, MAX802TESA+ application, or MAX802TESA+ equivalent, key selection criteria include guaranteed RESET assertion down to VCC = 1V, ±2% reset threshold accuracy, active-low open-drain RESET output, and support for lithium battery voltage exceeding VCC during normal operation.

Technical Context

The MAX802TESA+ integrates a precision reset comparator with 10mV hysteresis, a non-disableable 1.6s watchdog timer cleared by WDI transitions, and a dual-path battery switchover circuit that connects VOUT to VBATT when VCC falls below 2.40V (VSW) - enabling reliable CMOS RAM retention during brownout. Its PFI input supports external power-fail monitoring with 1.237V threshold and 10mV hysteresis.

It operates across –40°C to +85°C, draws only 40µA from VCC (at VCC < 3.6V), and features guaranteed RESET assertion even at VCC = 1V. The device uses an internal PMOS switch (3Ω typical on-resistance) for VCC-to-VOUT connection and a 140Ω switch for VBATT-to-VOUT path during backup mode.

Key Specifications

Pinout & Package

MAX802TESA+ is housed in an 8-pin SOIC package (SO, 150mil width), RoHS-compliant, with lead-free finish indicated by the '+' suffix.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MAX802TEPA+ and MAX706TESA+, the MAX802TESA+ delivers superior system-level reliability through integrated watchdog, precision ±2% reset threshold, and seamless VBATT switchover - making it optimal for battery-critical portable and industrial applications where feature completeness outweighs minor cost premium.

Availability

MAX802TESA+ is available at Aetrix Electronics and suitable for battery-powered computers, embedded controllers, intelligent instruments, and critical µP power monitoring requiring stable component supply across industrial temperature ranges.

Supply support for MAX802TESA+ 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) is a semiconductor company specializing in high-performance analog, mixed-signal, and power management ICs for industrial, communications, and computing markets.

The MAX802 series belongs to Maxim's microprocessor supervisory product line, designed specifically to replace discrete reset circuits in 3.0V/3.3V systems while adding watchdog, power-fail detection, and battery backup switching capabilities.

FAQ

What is the exact reset threshold voltage for MAX802TESA+ and how tight is its tolerance?

The MAX802TESA+ has a nominal reset threshold of 3.075V with a tolerance of ±2% over temperature and supply variation. This tighter tolerance compared to earlier families (e.g., ±4% for MAX690) ensures more deterministic reset timing in 3.3V systems with narrow supply margins. The specification is validated across –40°C to +85°C and applies to VCC falling conditions as defined in the MAX802T/S/R datasheet section "Reset Threshold".

Does MAX802TESA+ support lithium battery voltages higher than VCC, and how does switchover work?

Yes, MAX802TESA+ explicitly supports VBATT > VCC (e.g., 3.6V Li-cell with 3.3V VCC). Switchover occurs when VCC falls below 2.40V (VSW), connecting VOUT to VBATT through a 140Ω internal switch. On power-up, VOUT reconnects to VCC only after VCC rises above the reset threshold (3.075V), ensuring stable supply before RAM access resumes. This behavior is confirmed in the "Backup-Battery Switchover" section of the datasheet.

Is the watchdog timer in MAX802TESA+ disableable, and what is its timeout period?

No, the watchdog timer in MAX802TESA+ is non-disableable and has a fixed timeout period of 1.6 seconds ±40%. It clears on any edge (rising or falling) at the WDI pin and triggers RESET if no transition occurs within the timeout window. This design prevents accidental deactivation in safety-critical applications and is documented in the "Watchdog Input" subsection of the Detailed Description.

What is the function of the PFI and PFO pins on MAX802TESA+, and what voltage threshold do they use?

The PFI pin accepts an external voltage for power-fail monitoring, comparing it to a 1.237V internal reference (VPFT). When PFI falls below this threshold, the open-drain PFO pin pulls low. PFO can drive interrupts or be connected to MR on compatible parts (e.g., MAX704) to initiate reset. The 10mV typical hysteresis prevents chatter during slow voltage transitions, as specified in the Electrical Characteristics table under "PFI Input Threshold".

Can MAX802TESA+ operate reliably at VCC = 1V, and what happens to RESET at that voltage?

Yes, MAX802TESA+ guarantees RESET assertion (logic low) for all VCC values from 0V up to the reset threshold (3.075V), including at VCC = 1V. This is explicitly stated in the General Description and verified in the Absolute Maximum Ratings and Electrical Characteristics tables. At VCC = 1V, RESET remains asserted, holding the microprocessor in reset to prevent undefined operation - a key reliability feature for brownout resilience.