Analog Devices Inc. ADM802LARN-REEL

Overview

ADM802LARN-REEL from Analog Devices is a precision microprocessor supervisory circuit in SO-8 package, providing active-low reset assertion at 4.65 V threshold, 200 ms reset timeout, 1.6 s watchdog timer, and automatic battery switchover for CMOS RAM backup. It operates down to 1 V VCC and supports power-fail detection via 1.25 V PFI comparator in industrial temperature range (–40°C to +85°C).

For engineers reviewing the ADM802LARN-REEL datasheet, ADM802LARN-REEL pinout, ADM802LARN-REEL application, or ADM802LARN-REEL equivalent, key selection criteria include guaranteed reset accuracy (4.55 V to 4.70 V), ±2% PFI detection tolerance, 100 µA quiescent current, and SO-8 pin compatibility with legacy MAX802L designs.

Technical Context

The ADM802LARN-REEL integrates four core functions on a single die: a precision bandgap-based voltage monitor for VCC supervision, a transition-detecting watchdog timer with 1.6 s timeout, a battery switchover switch with <1 Ω on-resistance and 20 mV hysteresis, and an independent 1.25 V reference-based power-fail comparator with PFO open-drain output.

Its RESET output remains functional down to VCC = 1 V, ensuring reliable processor hold during brownout, while the WDI input accepts three-level logic (high/low/floating) to enable or disable watchdog functionality without external components. The PFI input draws only ±25 nA, enabling high-impedance resistive divider networks for flexible supply monitoring.

Key Specifications

Pinout & Package

ADM802LARN-REEL is housed in an 8-lead SOIC (SO-8) package per JEDEC MS-012, with 1.27 mm pitch, 5.0 mm × 4.0 mm body, and gull-wing leads. Pin 1 marked by notch or dot.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MAX802LCSA+, ADM802LARN-REEL reduces quiescent current by 17% and adds ±2% PFI accuracy; compared with TPS3823-46DBVR, it eliminates need for 3 external ICs (battery switch, PFI comparator, watchdog timer) while retaining SO-8 layout compatibility.

Availability

ADM802LARN-REEL is available at Aetrix Electronics and suitable for industrial automation, medical diagnostics, telecom infrastructure, and automotive infotainment systems requiring stable component supply, long-term lifecycle support, and guaranteed reset accuracy.

Supply support for ADM802LARN-REEL 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 semiconductor leader specializing in high-performance analog, mixed-signal, and digital signal processing technologies for precision measurement and control.

The ADM802L series belongs to Analog Devices' microprocessor supervisory product line, designed specifically to replace discrete reset/battery/PFI solutions in space- and power-constrained embedded systems with guaranteed industrial-grade reliability.

FAQ

What is the exact reset voltage threshold specification for ADM802LARN-REEL?

The ADM802LARN-REEL has a guaranteed reset voltage threshold of 4.55 V minimum and 4.70 V maximum at TA = 25°C with VCC falling, with 4.65 V nominal. This specification is validated across the full industrial temperature range (–40°C to +85°C) and ensures deterministic reset initiation in +5 V microprocessor systems without requiring external trimming.

Does ADM802LARN-REEL support battery backup for CMOS RAM, and what is its switchover behavior?

Yes, ADM802LARN-REEL supports automatic battery backup for CMOS RAM via its VBATT and VOUT pins. When VCC falls below the reset threshold and drops 20 mV below VBATT, the internal PMOS switch connects VBATT to VOUT. During switchover, VOUT maintains VBATT – 0.05 V at 250 µA load, and battery standby current is just 0.05 µA typical-enabling multi-year backup with standard 3 V lithium cells.

Can ADM802LARN-REEL be used without a backup battery, and how should unused pins be handled?

Yes, ADM802LARN-REEL operates fully without a backup battery: connect VBATT to GND and VOUT to VCC. Unused PFI should be tied to VCC or GND to disable the power-fail comparator; WDI may be left floating to disable the watchdog timer. No external pull-ups or pull-downs are required on RESET, PFO, or WDI-internal circuitry handles all default states.

What is the watchdog timeout period for ADM802LARN-REEL, and how is it reset?

The ADM802LARN-REEL watchdog timeout period is 1.6 s nominal (1.0–2.25 s range). It resets on every high-to-low or low-to-high transition at the WDI pin-no specific pulse width is required beyond the 50 ns minimum. If WDI remains static longer than the timeout, RESET asserts for 200 ms. The watchdog is disabled when WDI is floating or held at mid-supply.

How does the power-fail detection circuit in ADM802LARN-REEL work, and what accuracy does it provide?

The ADM802LARN-REEL power-fail detection uses an internal 1.25 V precision reference compared against the external PFI voltage. When PFI falls below 1.25 V, PFO goes low. Its PFI input accuracy is ±2% (1.225 V to 1.275 V), enabling reliable early-warning detection of supply sag. The PFI input draws only ±25 nA, allowing high-ratio resistor dividers for monitoring supplies up to 40 V.