Analog Devices Inc. ADM690AARM

Overview

ADM690AARM from Analog Devices is a precision microprocessor supervisory circuit in an 8-pin microSOIC package, providing active-low reset assertion at 4.65 V ±150 mV, 200 ms reset timeout, 1.6 s watchdog timer, and automatic battery switchover with <1 Ω on-resistance. It ensures reliable power-up/down/brownout reset for +5 V systems and supports CMOS RAM backup during main supply failure.

For engineers reviewing the ADM690AARM datasheet, ADM690AARM pinout, ADM690AARM application, or ADM690AARM equivalent, key selection criteria include guaranteed reset operation down to 1 V VCC, ±2% PFI threshold accuracy (1.25 V), low 100 µA quiescent current, and compatibility with industrial-temperature embedded controllers requiring stable brownout detection and watchdog supervision.

Technical Context

The ADM690AARM integrates four core functions: a precision voltage monitor with 4.65 V reset threshold, a 1.6 s watchdog transition detector that resets on missing WDI edge, a 1.25 V reference-based power fail comparator (PFI/PFO), and a bidirectional battery switchover switch connecting VBATT to VOUT when VCC drops below VBATT −20 mV. All logic outputs are open-drain or push-pull compatible with TTL/CMOS levels.

Its internal architecture uses an epitaxial CMOS process enabling operation from VCC = 1.0 V to 5.5 V and battery backup mode with only 0.05 µA standby current. The RESET output remains valid and asserted low even as VCC decays to 1 V, ensuring deterministic microprocessor hold during deep brownout.

Key Specifications

Pinout & Package

ADM690AARM is housed in an 8-lead microSOIC (RM-8) package measuring 3.10 mm × 3.05 mm × 0.938 mm, optimized for space-constrained PCB layouts while maintaining thermal performance (θJA = 110°C/W).

Key Features

Applications

Equivalent & Alternatives

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

Compared with MAX690A and TPS3808G18, the ADM690AARM uniquely combines guaranteed 1 V reset operation, integrated battery switchover with hysteresis, and a 1.6 s watchdog in a space-saving microSOIC package-making it optimal for industrial and medical systems demanding high reliability and minimal board area.

Availability

ADM690AARM is available at Aetrix Electronics and suitable for industrial PLC controllers, medical diagnostic instruments, telecom line cards, and automotive infotainment modules requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for ADM690AARM 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, communications, and automotive markets since 1965.

The ADM690AARM belongs to Analog Devices' microprocessor supervisory circuit family, designed specifically for robust power monitoring, reset generation, and battery backup management in mission-critical embedded systems.

FAQ

What is the guaranteed minimum VCC level at which ADM690AARM continues to assert RESET?

The ADM690AARM guarantees RESET assertion down to VCC = 1.0 V, ensuring the microprocessor remains held in reset during deep brownout conditions. This behavior is verified across the full industrial temperature range (–40°C to +85°C) and is critical for preventing undefined MCU states. The ADM690AARM achieves this via internal rail-to-rail comparator design and low-threshold output drivers, unlike many competitors that release reset above 2.5 V.

Does ADM690AARM support active-high reset output?

No, the ADM690AARM provides only active-low RESET output. Active-high reset (RESET) is exclusive to the ADM805L/M variants. Attempting to invert ADM690AARM's RESET output externally does not replicate the timing or drive strength of the dedicated ADM805L/M output. For active-high requirements, the ADM805LARM or ADM805MARM must be selected instead of ADM690AARM.

How does the ADM690AARM battery switchover function during power-up?

During power-up, ADM690AARM switches VOUT from VBATT to VCC when VCC rises to VBATT + 20 mV, with 40 mV hysteresis preventing chatter. This ensures clean transition without voltage droop on VOUT. The internal PMOS switch exhibits <1 Ω on-resistance, supporting up to 100 mA continuous load. If VBATT is unconnected, it must be tied to GND to avoid undefined behavior.

Can the watchdog timer in ADM690AARM be disabled without hardware modification?

Yes, the ADM690AARM watchdog timer is automatically disabled when the WDI pin is left floating or connected to a high-impedance (three-state) logic output. No external pull-up/down resistors are required. This allows firmware-controlled enable/disable without PCB changes. However, tying WDI directly to VCC or GND will cause continuous reset assertion due to lack of transitions.

What is the accuracy of the PFI input threshold in ADM690AARM?

The ADM690AARM PFI input threshold is 1.25 V with a tolerance of ±25 mV (±2%) over temperature and supply, as specified in the datasheet. This accuracy enables precise power-fail detection using standard 1% resistors in the external divider network. The internal 1.25 V reference is trimmed and stable, eliminating need for external reference ICs in most implementations.