Analog Devices Inc. ADM8691ARW-REEL

Overview

ADM8691ARW-REEL from Analog Devices is a 16-pin TSSOP microprocessor supervisory circuit integrating power-on/brownout reset, adjustable watchdog timer (100 ms / 1.6 s / adjustable), battery backup switchover (VBATT to VOUT), power-fail warning (1.3 V PFI threshold), and CE gating with 3 ns propagation delay. It supports 5 V systems with 4.65 V reset threshold and operates from −40°C to +85°C.

For engineers reviewing the ADM8691ARW-REEL datasheet, ADM8691ARW-REEL pinout, ADM8691ARW-REEL application, or ADM8691ARW-REEL equivalent, key selection considerations include its dual reset timeout options (50 ms / adjustable), active-low RESET + active-high LOW LINE outputs, BATT ON drive capability for external PNP transistors, and integrated RAM write protection via CEIN/CEOUT.

Technical Context

The ADM8691ARW-REEL implements a dual-mode oscillator architecture: internal oscillator (enabled when OSC SEL = high/floating) selects fixed watchdog periods (100 ms or 1.6 s), while OSC SEL = low enables external clock or capacitor-based timing for adjustable reset pulse width and watchdog timeout. Its reset generator guarantees operation down to VCC = 1 V and includes 40 mV hysteresis for noise immunity.

It integrates three independent monitoring paths: (1) 4.65 V VCC reset comparator with 50 ms nominal timeout, (2) 1.3 V PFI comparator driving open-drain PFO output, and (3) three-level WDI input supporting watchdog disable via floating/midsupply bias. Battery switchover uses PMOS/NMOS switching with 70 mV rise / 50 mV fall thresholds and 20 mV hysteresis.

Key Specifications

Pinout & Package

ADM8691ARW-REEL is housed in a 16-lead TSSOP package (4.4 mm × 5.0 mm, 0.65 mm pitch), compatible with surface-mount reflow assembly and offering thermal performance of θ_JA = 158°C/W.

Key Features

Applications

Equivalent & Alternatives

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

Compared with ADM8695ARW-REEL, ADM8691ARW-REEL offers shorter default reset duration for faster recovery; versus MAX691CPD+, it adds CE gating, adjustable timing, and dual reset outputs - enabling more robust data integrity in complex embedded systems.

Availability

ADM8691ARW-REEL is available at Aetrix Electronics and suitable for industrial PLC control, automotive infotainment, medical diagnostic equipment, network router management CPUs, and portable instrumentation requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for ADM8691ARW-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 leader in high-performance analog, mixed-signal, and digital signal processing semiconductors, serving industrial, automotive, communications, and healthcare markets.

The ADM8691ARW-REEL belongs to Analog Devices' microprocessor supervisory circuit family, designed specifically to ensure reliable power sequencing, data integrity, and fault recovery in mission-critical embedded systems operating under variable supply conditions.

FAQ

What is the guaranteed minimum operating VCC voltage for ADM8691ARW-REEL reset functionality?

The ADM8691ARW-REEL guarantees RESET output functionality down to VCC = 1 V, ensuring the microprocessor remains held in reset during deep brownout conditions. This specification is validated across the full −40°C to +85°C industrial temperature range and is independent of VBATT presence. The internal reset comparator continues asserting low on the RESET pin until VCC rises above the 4.65 V threshold with hysteresis.

How does ADM8691ARW-REEL implement battery backup switchover, and what is the voltage hysteresis?

The ADM8691ARW-REEL uses internal PMOS/NMOS switches to route either VCC or VBATT to VOUT, selecting the higher source. Switchover occurs at VCC − VBATT = 70 mV (rising) and 50 mV (falling), yielding 20 mV hysteresis to prevent oscillation during slow supply decay. In battery mode, VOUT tracks VBATT with ≤5 mV dropout at 250 μA, and supply current drops to 0.4 μA - enabling multi-year backup with lithium coin cells.

Can ADM8691ARW-REEL's watchdog timer be disabled, and how?

Yes, the ADM8691ARW-REEL watchdog timer can be disabled by leaving the WDI pin floating or biasing it to approximately VCC/2 (midsupply). In this state, the internal three-level input detects indeterminate logic and inhibits timeout counting. WDO remains high, and RESET is not asserted due to watchdog expiration. This allows safe operation in systems where continuous WDI toggling is impractical, without requiring hardware modification.

What is the function of the CEIN and CEOUT pins on ADM8691ARW-REEL, and how do they protect memory?

The CEIN pin accepts the system's chip-enable signal, and CEOUT delivers a gated replica with 3 ns propagation delay. When VCC remains above 4.65 V, CEOUT mirrors CEIN; if VCC falls below threshold, CEOUT is forced high - disabling writes to battery-backed RAM or EEPROM. This prevents partial or corrupted writes during power transitions, directly protecting data integrity without external logic or firmware intervention in the ADM8691ARW-REEL design.

Does ADM8691ARW-REEL support both active-low and active-high reset outputs, and how are they used?

Yes, ADM8691ARW-REEL provides two dedicated reset outputs: pin 15 (RESET) is active-low, and pin 16 (RESET) is active-high - electrically complementary. This dual-output architecture eliminates the need for external inverters when interfacing with processors requiring opposite reset polarities. Both outputs assert synchronously during VCC undervoltage or watchdog timeout, and both remain functional down to VCC = 1 V, ensuring consistent reset behavior across diverse host microcontrollers.