Analog Devices Inc. ADM690AARN

Overview

ADM690AARN from Analog Devices is a precision microprocessor supervisory circuit in SO-8 package, providing active-low reset (RESET), watchdog timer (1.6 s timeout), battery switchover, and power-fail detection (1.25 V threshold). It asserts reset down to 1 V VCC and supports CMOS RAM backup in embedded controllers and industrial instrumentation.

For engineers reviewing the ADM690AARN datasheet, ADM690AARN pinout, ADM690AARN application, or ADM690AARN equivalent, key selection criteria include its 4.65 V reset threshold, 200 ms reset timeout, battery switchover hysteresis (40 mV), PFI comparator accuracy (±2% on related variants), and SO-8 footprint compatibility with legacy MAX690A designs.

Technical Context

The ADM690AARN integrates four core functions: a precision voltage monitor with 4.65 V reset threshold and 40 mV hysteresis; a transition-detecting watchdog timer with 1.6 s timeout and 50 ns minimum WDI pulse width; an automatic battery switchover circuit with <20 mV switchover threshold and 0.05 µA standby current; and a 1.25 V reference-based power-fail comparator (PFI/PFO) with ±2% accuracy on ADM802L/M variants.

Its internal architecture uses an epitaxial CMOS process enabling operation down to 1 V VCC while maintaining RESET assertion, and features a low-dropout PMOS switch (<1 Ω on-resistance) for VOUT switching between VCC and VBATT - critical for reliable RAM retention during brownout.

Key Specifications

Pinout & Package

ADM690AARN is housed in an 8-lead SOIC (SO-8) package, 3.9 mm × 4.9 mm, with standard 1.27 mm pitch and gull-wing leads. Pin 1 marked by notch or dot; thermal impedance θ_JA = 110°C/W.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MAX690AAN, ADM690AARN delivers lower supply current and guaranteed 1 V reset operation; compared with ADM802LARN, it trades PFI accuracy for broader industry adoption history and identical core supervision functionality at lower cost.

Availability

ADM690AARN is available at Aetrix Electronics and suitable for industrial PLC controllers, medical diagnostic instruments, and telecom line cards requiring stable component supply, long-term lifecycle support, and SO-8 footprint compatibility.

Supply support for ADM690AARN 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, Inc. is a global semiconductor leader specializing in high-performance analog, mixed-signal, and digital signal processing technologies for precision measurement and control systems.

The ADM690AARN belongs to Analog Devices' microprocessor supervisory circuit product line, engineered for robust power monitoring, fail-safe reset generation, and battery-backed memory retention in mission-critical embedded systems.

FAQ

What is the reset voltage threshold for ADM690AARN?

The ADM690AARN has a nominal reset voltage threshold of 4.65 V, with guaranteed min/max values of 4.5 V and 4.75 V respectively. This threshold is fixed and applies across the full industrial temperature range (–40°C to +85°C). The ADM690AARN uses this threshold to assert the active-low RESET output whenever VCC falls below the specified level, ensuring reliable microprocessor reset during brownout conditions.

Does ADM690AARN support battery backup switching, and what is its switchover behavior?

Yes, ADM690AARN supports automatic battery backup switching between VCC and VBATT. When VCC drops below VBATT by 20 mV, VOUT switches from VCC to VBATT; on power-up, VOUT switches back when VCC rises 20 mV above VBATT. The switchover hysteresis is 40 mV, preventing oscillation near the threshold. In battery backup mode, VOUT delivers VBATT – 0.002 V at 250 µA load, with standby current as low as 0.05 µA.

Can the watchdog timer in ADM690AARN be disabled, and how?

Yes, the watchdog timer in ADM690AARN can be disabled by leaving the WDI pin floating or connecting it to a high-impedance (three-state) logic output. The device detects high-impedance states and halts the 1.6 s timeout counter. No external pull-up or pull-down is required. When enabled, WDI requires a transition (high-to-low or low-to-high) at least every 1.6 s to prevent RESET assertion - a feature confirmed in the functional block diagram and timing specifications.

What is the purpose of the PFI and PFO pins on ADM690AARN?

The PFI (Power Fail Input) pin connects to a resistive divider monitoring an external power rail; it compares that voltage against an internal 1.25 V reference. When PFI falls below 1.25 V, the PFO (Power Fail Output) pin goes low to signal impending power loss. This allows the microprocessor to execute an orderly shutdown. While ADM690AARN specifies the 1.25 V reference, PFI accuracy is not explicitly rated in its datasheet - unlike the ADM802L/M variants which guarantee ±2%.

Is ADM690AARN pin-compatible with MAX690A, and what are the key improvements?

Yes, ADM690AARN is pin-compatible with MAX690A in SO-8 package and serves as a direct upgrade. Key improvements include guaranteed RESET assertion down to 1 V VCC (vs. unspecified minimum for MAX690A), lower max supply current (100 µA vs. 120 µA), tighter reset threshold tolerance (±150 mV vs. ±250 mV), and integrated battery switchover hysteresis (40 mV). These enhancements improve reliability in deep brownout and low-power backup scenarios.