Analog Devices Inc. ADM805LAN

Overview

ADM805LAN from Analog Devices is a precision microprocessor supervisory circuit in 8-pin DIP package, providing active-high RESET output, 4.65 V supply voltage monitoring, 200 ms reset timeout, and integrated battery switchover for CMOS RAM backup. It operates across –40°C to +85°C and asserts RESET down to VCC = 1 V, enabling reliable system initialization and brownout protection in embedded controllers.

For engineers reviewing the ADM805LAN datasheet, ADM805LAN pinout, ADM805LAN application, or ADM805LAN equivalent, key selection criteria include its active-high reset logic, 4.65 V threshold tolerance (±150 mV), watchdog timer disable capability via floating WDI, and compatibility with 3 V backup batteries in industrial power monitoring systems.

Technical Context

The ADM805LAN integrates four core functions: a precision 4.65 V VCC monitor with 40 mV hysteresis, a 1.6 s watchdog timer triggered by WDI transitions, automatic battery switchover with 20 mV switchover threshold and 40 mV hysteresis, and a 1.25 V reference-based power fail comparator (PFI/PFO). All functions operate independently and remain functional at VCC as low as 1 V.

Its internal PMOS switch delivers VOUT with <1 Ω on-resistance in normal mode and supports up to 100 mA load; in battery backup mode, it connects VBATT to VOUT with <0.05 µA standby current and dropout <5 mV at 250 µA, ensuring ultra-low-power RAM retention.

Key Specifications

Pinout & Package

ADM805LAN uses an 8-pin plastic DIP (N-8) package with 0.3 inch width, 0.1 inch lead pitch, and through-hole mounting. Pin 1 is marked with notch or dot; leads are tin-lead plated for solderability.

Key Features

Applications

Equivalent & Alternatives

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

Compared with ADM805LARN, ADM805LAN offers easier manual soldering and thermal margin in low-airflow enclosures; versus MAX805L, it delivers lower quiescent current and tighter reset threshold accuracy-critical for long-life battery-backed instrumentation.

Availability

ADM805LAN is available at Aetrix Electronics and suitable for industrial PLC controllers, medical diagnostic instruments, telecom remote terminal units, and automotive body control modules requiring stable component supply across extended temperature ranges and long product lifecycles.

Supply support for ADM805LAN 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

Analog Devices is a global leader in high-performance analog, mixed-signal, and digital signal processing semiconductors, serving industrial, automotive, communications, and healthcare markets since 1965.

The ADM690A/ADM805L/M family was designed specifically for robust power supervision in microprocessor-based systems where deterministic reset timing, battery-backed memory retention, and watchdog reliability are mission-critical.

FAQ

What is the reset output polarity of ADM805LAN?

The ADM805LAN features an active-high RESET output, which is the complement of the standard active-low RESET signal. This means ADM805LAN drives RESET high when VCC falls below 4.65 V or when the watchdog timer times out after 1.6 s. The high-level output voltage equals the higher of VCC or VBATT, making it directly compatible with processors requiring active-high reset assertion without external inversion logic.

Can ADM805LAN operate with VCC below 4.65 V and still assert RESET?

Yes-ADM805LAN guarantees RESET assertion down to VCC = 1 V. When VCC drops below the 4.65 V threshold, RESET goes high and remains asserted for a minimum of 140 ms (typical 200 ms) after VCC rises back above threshold. Even at VCC = 1 V, ADM805LAN sustains valid RESET logic levels (≥0.8 V high, ≤0.4 V low), ensuring reliable microprocessor hold during deep brownout recovery.

How does the battery switchover function work in ADM805LAN?

In ADM805LAN, battery switchover activates when VCC falls below VBATT by 20 mV (with 40 mV hysteresis). At that point, the internal PMOS switch disconnects VCC from VOUT and connects VBATT instead. VOUT then supplies backup power to attached RAM or logic, drawing only 0.05 µA from VBATT. On power-up, VOUT reverts to VCC once VCC exceeds VBATT by 20 mV-enabling seamless, glitch-free transition without spurious resets during battery replacement.

Is the watchdog timer in ADM805LAN enabled by default?

No-the watchdog timer in ADM805LAN is disabled by default and requires active toggling of the WDI pin to enable supervision. If WDI is left floating or connected to a high-impedance (tri-state) output, the watchdog remains inactive and will not generate RESET pulses. To activate it, the host microprocessor must toggle WDI (high-to-low or low-to-high) at least once every 1.6 seconds; failure to do so forces RESET high for 200 ms.

What is the purpose of the PFI and PFO pins on ADM805LAN?

The PFI (Power Fail Input) and PFO (Power Fail Output) pins on ADM805LAN implement an independent 1.25 V comparator for early power failure detection. PFI accepts a scaled-down version of the main supply (via external resistor divider); when PFI voltage drops below 1.25 V, PFO pulls low to signal impending power loss. This allows the system to initiate controlled shutdown, save state, or trigger backup power sequencing-functioning completely separately from the main reset generator and watchdog circuits.