Analog Devices Inc. ADM802LARN

Overview

ADM802LARN from Analog Devices is a precision microprocessor supervisory circuit in SO-8 package, providing active-low reset assertion at 4.65 V ±50 mV, 200 ms reset timeout, 1.6 s watchdog timer, and automatic battery switchover for CMOS RAM backup. It operates with VCC as low as 1 V and supports power-fail detection via 1.25 V PFI threshold.

For engineers reviewing the ADM802LARN datasheet, ADM802LARN pinout, ADM802LARN application, or ADM802LARN equivalent, key selection criteria include guaranteed reset voltage accuracy (±50 mV), battery switchover hysteresis (40 mV), quiescent current (100 µA), and compatibility with 5 V microprocessor systems requiring reliable brownout and watchdog protection.

Technical Context

The ADM802LARN integrates four core functions: a precision bandgap-based voltage monitor with 4.65 V reset threshold, a monostable watchdog timer triggered by WDI transitions, an internal PMOS battery switchover switch with <1 Ω on-resistance, and a dedicated 1.25 V reference comparator for PFI/PFO power-fail signaling.

Its reset generator guarantees assertion down to VCC = 1 V, while the battery switchover circuit activates when VCC falls 20 mV below VBATT and deactivates when VCC rises 20 mV above VBATT - both with 40 mV hysteresis. The PFI input draws only ±25 nA, enabling high-impedance resistive divider networks for accurate power-fail threshold setting.

Key Specifications

Pinout & Package

ADM802LARN is housed in an 8-lead SOIC (SO-8) package measuring 4.90 mm × 3.90 mm × 1.75 mm, with gull-wing leads and standard JEDEC MS-012AC footprint.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MAX802LCSA+, ADM802LARN offers lower quiescent current and same functional coverage; versus TPS3808G18DBVR, ADM802LARN provides integrated battery switchover and watchdog - eliminating two external ICs and simplifying layout in space-constrained embedded systems.

Availability

ADM802LARN is available at Aetrix Electronics and suitable for industrial automation, medical device, and network infrastructure applications requiring stable component supply, long-lifecycle support, and guaranteed reset accuracy across temperature.

Supply support for ADM802LARN 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.

The ADM690A/ADM802L/M family was designed specifically for robust power supervision in 5 V microprocessor systems - delivering integrated reset, watchdog, battery switchover, and power-fail detection in a single SO-8 package.

FAQ

What is the guaranteed reset voltage threshold tolerance for ADM802LARN?

The ADM802LARN has a guaranteed reset voltage threshold of 4.65 V with a minimum of 4.55 V and maximum of 4.70 V at TA = 25°C under VCC falling conditions. This ±50 mV tolerance ensures consistent brownout detection across production units and temperature ranges, making ADM802LARN suitable for applications demanding tight supply monitoring in industrial environments.

Does ADM802LARN support battery backup for CMOS RAM, and how does switchover work?

Yes, ADM802LARN supports automatic battery backup for CMOS RAM via its VBATT and VOUT pins. When VCC falls 20 mV below VBATT, the internal PMOS switch connects VBATT to VOUT; when VCC rises 20 mV above VBATT, it reconnects VCC to VOUT - both with 40 mV hysteresis. This eliminates external diodes and ensures seamless RAM power continuity without voltage drop, a core capability of ADM802LARN.

Can the watchdog timer in ADM802LARN be disabled, and how?

Yes, the watchdog timer in ADM802LARN can be disabled by leaving the WDI pin floating or connecting it to a high-impedance (three-stated) logic output. The device detects high-impedance states and halts watchdog timing, allowing full use of RESET and battery functions without software intervention. This behavior is explicitly specified in the ADM802LARN datasheet and requires no configuration register writes.

What is the maximum load current ADM802LARN can deliver on VOUT in battery backup mode?

In battery backup mode, ADM802LARN delivers up to 250 µA on VOUT with a dropout voltage of VBATT − 0.002 V, as verified in the datasheet's "VOUT in Battery Backup Mode" specification. This current level is optimized for low-power CMOS RAM and real-time clocks - not for high-current peripherals. For higher loads, an external buffer or capacitor is required, per ADM802LARN application guidance.

Is ADM802LARN compatible with 3.3 V microprocessor systems?

No, ADM802LARN is not compatible with 3.3 V microprocessor systems. It is specified for VCC = 4.75 V to 5.5 V operation and features a fixed 4.65 V reset threshold - intended exclusively for 5 V logic families. Using ADM802LARN with 3.3 V supplies would result in continuous reset assertion. For 3.3 V systems, Analog Devices recommends the ADM809/ADM810 series, not ADM802LARN.