Analog Devices Inc./Maxim Integrated MAX805LMJA

Overview

MAX805LMJA from Maxim Integrated is a microprocessor supervisory circuit designed for high-reliability embedded systems operating across -55°C to +125°C. It provides active-high reset assertion (RESET), power-fail warning (PFO), watchdog timeout (1.6s), battery-backup switchover, and 4.65V supply monitoring - all in an 8-pin CERDIP package. Used in aerospace, military, and industrial control systems where extended temperature operation and deterministic reset behavior are critical.

For engineers reviewing the MAX805LMJA datasheet, MAX805LMJA pinout, MAX805LMJA application, or MAX805LMJA equivalent, this page delivers verified functional identity, validated thermal and electrical specs, confirmed pin roles, real-world use cases in harsh environments, and two rigorously cross-checked alternative parts with documented technical differences.

Technical Context

The MAX805LMJA integrates a precision 4.65V reset threshold detector with hysteresis (40mV), a 200ms reset pulse generator, and a 1.6s watchdog timer cleared by WDI edge transitions. Its active-high RESET output remains valid down to VCC = 1.1V, enabling compatibility with Intel 80C51-family microcontrollers requiring high-true reset signaling.

It features dual-supply management: VOUT connects to VCC above reset threshold via a 5Ω PMOS switch, and switches to VBATT (if > VCC +20mV) below threshold via an 80Ω PMOS switch. The 1.25V internal reference powers the PFI comparator, supporting external undervoltage detection independent of main supply rails.

Key Specifications

Pinout & Package

MAX805LMJA is housed in an 8-pin CERDIP (ceramic dual in-line package) with hermetic sealing, lead-free finish (per MIL-STD-883), and substrate left unconnected per datasheet requirement. Pin spacing conforms to JEDEC MS-001 standard (0.300" wide body, 0.100" lead pitch).

Key Features

Applications

Equivalent & Alternatives

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

Compared with MAX805LMJA, MAX805LESA trades hermetic reliability and extended temperature for surface-mount convenience, while MAX692AMJA retains identical rugged packaging but shifts reset threshold downward for higher noise immunity in less regulated supplies.

Availability

MAX805LMJA is available at Aetrix Electronics and suitable for aerospace avionics, military vehicle ECUs, and downhole instrumentation requiring stable component supply across extreme temperature cycles and long product lifecycles.

Supply support for MAX805LMJA 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 MAX805L series was developed specifically for high-reliability microprocessor supervision in harsh environments, emphasizing guaranteed reset behavior, low-power backup operation, and extended temperature qualification.

FAQ

What is the guaranteed minimum VCC level at which MAX805LMJA asserts RESET?

The MAX805LMJA guarantees RESET assertion down to VCC = 1.1V, ensuring reliable hold-down during deep brownout conditions. This specification is explicitly tested and guaranteed across the full -55°C to +125°C operating range, unlike many supervisory ICs that degrade below 2.0V. The active-high RESET output remains valid and drives high throughout this range, making MAX805LMJA suitable for systems where supply collapse is gradual or prolonged.

Does MAX805LMJA support watchdog functionality, and how is it enabled?

Yes, MAX805LMJA includes a 1.6s watchdog timer monitored via the WDI pin. The timer clears on any rising or falling edge at WDI and triggers RESET if no transition occurs within 1.6s (typical). To enable it, connect WDI to a GPIO pin toggled by firmware; leaving WDI floating or tied to a high-impedance state disables the watchdog. The MAX805LMJA datasheet confirms this behavior is identical to the MAX690A/MAX802L family.

Can MAX805LMJA operate with a 3.3V main supply instead of +5V?

No - MAX805LMJA is specified only for VCC = 4.75V to 5.5V (per Electrical Characteristics table). Its 4.65V reset threshold and internal 1.25V reference assume a nominal +5V rail. Using 3.3V would prevent proper reset assertion and disable PFI comparator operation. For 3.3V systems, consider MAX6326 or MAX6369 families, which are explicitly rated for 2.5V–5.5V operation.

What is the maximum allowable VBATT voltage for MAX805LMJA, and why is this limit critical?

The maximum allowable VBATT voltage for MAX805LMJA is 4.80V, as stated in Table 2 of the datasheet. Exceeding this risks forward-biasing the internal substrate diode (D1 in Figure 3) when VCC approaches the reset threshold, causing unintended current flow from VBATT into the die. This can disrupt regulation, increase leakage, and compromise long-term reliability - especially in hermetic CERDIP packages where heat dissipation is limited.

Is MAX805LMJA pin-compatible with MAX690AMJA or MAX802LMJA?

Yes - MAX805LMJA is pin-compatible with MAX690AMJA and MAX802LMJA. All three share identical 8-pin CERDIP packaging, identical pinout (VOUT, VCC, GND, PFI, PFO, WDI, RESET, VBATT), and identical thermal and mechanical footprints. However, MAX690AMJA provides active-low RESET, while MAX805LMJA provides active-high RESET; this functional difference requires corresponding μP reset pin configuration changes.