Analog Devices Inc./Maxim Integrated MAX802LESA+

Overview

MAX802LESA+ from Maxim Integrated is a microprocessor supervisory circuit providing power-on reset, battery-backup switching, watchdog timer, and power-fail detection for +5V systems. It asserts an active-low RESET pulse for 200ms during power-up, brownout (VCC < 4.65V), or watchdog timeout (1.6s), supports CMOS RAM backup via VOUT with ±2% power-fail accuracy, and operates across –40°C to +85°C in 8-pin SO package.

For engineers reviewing the MAX802LESA+ datasheet, MAX802LESA+ pinout, MAX802LESA+ application, or MAX802LESA+ equivalent, this page delivers verified technical context, exact pin functions, real-world use cases in battery-powered controllers and critical μP monitoring, and validated alternative parts with documented functional and application differences.

Technical Context

The MAX802LESA+ integrates four core functions on a single die: a precision 4.65V reset threshold detector with 40mV hysteresis, a 1.6s watchdog timer cleared by WDI edges or RESET assertion, a battery switchover circuit that connects VBATT to VOUT only when VCC falls below 4.65V and VBATT exceeds VCC by ≥20mV, and a 1.25V reference-based power-fail comparator driving PFO.

Its internal architecture uses a P-channel MOSFET for VOUT switching (5Ω on-resistance in VCC mode, 80Ω in VBATT mode), guarantees RESET assertion down to VCC = 1V, draws just 200µA quiescent current under normal operation and 50nA in battery-backup mode, and features logic-level WDI input with 50kΩ internal bias and 50ns minimum pulse width detection.

Key Specifications

Pinout & Package

MAX802LESA+ is housed in an 8-pin SOIC package (SO-8, 150mil width, RoHS-compliant with + suffix), with gull-wing leads, 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 MAX802LESA+, MAX802MESA+ offers identical functionality with a lower reset threshold for wider supply tolerance, while MAX706PESA+ sacrifices watchdog and battery support to enable ultra-low-voltage operation-neither is pin-compatible nor functionally interchangeable without schematic revision.

Availability

MAX802LESA+ is available at Aetrix Electronics and suitable for battery-powered controllers, critical μP power monitoring, and intelligent instruments requiring stable component supply across industrial temperature ranges and long-life backup operation.

Supply support for MAX802LESA+ 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, medical, and communications applications.

The MAX802L series belongs to Maxim's microprocessor supervisory product line, designed specifically to replace discrete reset generators and battery switchover circuits in +5V μP systems with guaranteed timing, precision thresholds, and low-power operation.

FAQ

What is the guaranteed reset threshold voltage for MAX802LESA+?

The MAX802LESA+ has a guaranteed reset threshold of 4.65V with ±2% tolerance over the full –40°C to +85°C temperature range. This value is specified in the Electrical Characteristics table under "Reset Threshold (VRT)" for MAX802L devices, and applies to both rising and falling VCC transitions with 40mV hysteresis. The MAX802LESA+ uses this precise threshold to trigger RESET during power-up, brownout, or power-down conditions in +5V systems.

Does MAX802LESA+ support active-high reset output?

No, the MAX802LESA+ provides only an active-low RESET output (pin 7). It does not include the active-high RESET output found on the MAX805L variant. If an active-high reset signal is required-for example, for Intel 80C51-family microprocessors-a level-shifting buffer or external inverter must be added. The MAX802LESA+ datasheet explicitly states that RESET is the sole reset output, and the MAX805L is the designated part number for active-high functionality.

What is the maximum allowable backup battery voltage for MAX802LESA+?

The maximum allowable backup battery voltage for MAX802LESA+ is 4.80V, as specified in Table 2 of the datasheet under "Allowable Backup-Battery Voltages." Exceeding this voltage risks forward-biasing the internal substrate diode (D1) when VCC is near the reset threshold, causing unintended current flow from VBATT to VCC and potential damage or erratic behavior. Lithium cells with open-circuit voltages of 3.0V–3.6V are ideal and require no additional protection circuitry.

How does the watchdog timer in MAX802LESA+ behave during power-up?

The watchdog timer in MAX802LESA+ is automatically cleared during power-up and remains disabled until RESET is deasserted and WDI receives its first valid edge. As stated in the Detailed Description section, "the internal watchdog timer clears whenever reset is asserted, WDI is three-stated, or WDI sees a rising or falling edge." Therefore, the 1.6s timeout period begins only after the initial 200ms RESET pulse ends and the host μP begins toggling WDI-preventing spurious resets during boot sequence.

Can MAX802LESA+ operate without a backup battery connected?

Yes, MAX802LESA+ can operate without a backup battery. Per the Applications Information section, if no backup source is used, VBATT should be grounded and VOUT connected directly to VCC. This bypasses the internal battery switchover circuitry, eliminates voltage drop across the PMOS switch, and ensures VOUT tracks VCC precisely. The device continues to provide full reset generation, watchdog, and power-fail monitoring functionality with no performance degradation.