Analog Devices Inc. ADM691AARN

Overview

ADM691AARN from Analog Devices is a microprocessor supervisory circuit providing precision 4.65 V ±3% reset threshold, 200 ms or adjustable reset timeout, 100 ms/1.6 s selectable watchdog timer, automatic battery backup switchover (VCC/VBATT), and chip enable gating - all in a 16-lead narrow SOIC package. It ensures reliable power-up/down/brownout reset, RAM write protection, and early power-fail warning in embedded control systems.

For engineers reviewing the ADM691AARN datasheet, ADM691AARN pinout, ADM691AARN application, or ADM691AARN equivalent, this device supports critical design tasks including µP reset timing validation, battery-backed memory integrity assurance, watchdog timeout configuration via OSC IN/OSC SEL, and PFI-based early power-fail interrupt generation for NMI-driven data save routines.

Technical Context

The ADM691AARN integrates a precision bandgap voltage detector (4.65 V threshold with 15 mV hysteresis), an internal oscillator with dual watchdog modes (100 ms short / 1.6 s long), and a bidirectional battery switchover switch with <0.8 Ω VCC-to-VOUT on-resistance and 7 Ω VBATT-to-VOUT resistance. Its CE gating circuit provides 6–10 ns propagation delay and 40–150 Ω ON-resistance between CEIN and CEOUT.

Reset assertion remains active down to VCC = 1 V; in battery backup mode, supply current drops to 0.04 µA typical, and RESET output stays low while WDI, OSC IN, and OSC SEL are disabled. The 1.25 V PFI comparator operates independently during backup if VCC ≥ VBATT – 1.2 V.

Key Specifications

Pinout & Package

ADM691AARN is housed in a 16-lead narrow SOIC (R-16N) package, 7.5 mm × 5.3 mm, 1.27 mm pitch, gull-wing leads. Pin 1 is VBATT; pin 4 is GND; pin 15/16 are complementary open-drain RESET outputs.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MAX691ACPE+, ADM691AARN offers 20× lower battery backup current and SOIC/TSSOP packaging flexibility; versus TPS3823DBVR, it delivers full supervisory integration - eliminating 3–4 discrete components in µP systems requiring RAM backup, watchdog, and power-fail warning.

Availability

ADM691AARN is available at Aetrix Electronics and suitable for industrial PLC controllers, automotive body control modules, medical infusion pumps, and point-of-sale terminals requiring stable component supply, long-term lifecycle support, and guaranteed industrial temperature operation.

Supply support for ADM691AARN 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 ADM691AARN belongs to Analog Devices' microprocessor supervisory IC product line, designed specifically to consolidate reset, watchdog, battery switchover, CE gating, and power-fail warning into a single IC for resource-constrained embedded systems.

FAQ

What is the reset voltage threshold accuracy of the ADM691AARN?

The ADM691AARN features a guaranteed reset voltage threshold of 4.65 V ±3%, meaning the actual trip point falls between 4.50 V and 4.75 V across temperature and supply variations. This tight tolerance ensures compatibility with +5 V ±5% power supplies and prevents premature or delayed reset assertion in industrial applications where supply regulation is marginal.

How does the ADM691AARN handle battery backup switchover during power failure?

The ADM691AARN automatically switches VOUT from VCC to VBATT when VCC drops below VBATT + 0.03 V during power-down, with 60 mV hysteresis to prevent chatter. In battery mode, VOUT delivers VBATT – 0.15 V at 5 mA (VBATT = 2.0 V), with typical supply current of 0.04 µA - enabling multi-year operation from a CR2032 coin cell in memory-retention applications.

Can the watchdog timeout period of the ADM691AARN be adjusted, and how?

Yes, the ADM691AARN watchdog timeout can be set to 100 ms, 1.6 s, or made adjustable using an external capacitor on OSC IN. With OSC SEL floating and OSC IN grounded, timeout is 100 ms; with both pins floating, it is 1.6 s; with OSC SEL low and a capacitor (C) from OSC IN to GND, timeout = 600 × (C/47 pF) ms - enabling precise tuning from ~100 ms to several seconds.

What is the function of the CEIN and CEOUT pins on the ADM691AARN?

CEIN accepts the microprocessor's chip enable or write signal; CEOUT replicates it with 6–10 ns delay during normal operation but forces high during reset or brownout - blocking writes to battery-backed CMOS RAM or EEPROM. This prevents data corruption when VCC is unstable, and eliminates need for external logic to gate memory access during power transitions.

Does the ADM691AARN support early power-fail detection, and how is it implemented?

Yes, the ADM691AARN implements early power-fail detection via its PFI (Power Fail Input) and PFO (Power Fail Output) pins. PFI compares an external voltage (e.g., from a resistor divider on the unregulated input) against an internal 1.25 V reference; when PFI falls below 1.25 V, PFO asserts low within 25–60 µs to trigger an NMI interrupt, allowing the µP to save critical data before VCC crosses the 4.65 V reset threshold.