Analog Devices Inc. ADM8691ARUZ

Overview

ADM8691ARUZ from Analog Devices is a 16-pin TSSOP microprocessor supervisory circuit providing precision reset generation (4.65 V threshold), adjustable watchdog timeout (100 ms / 1.6 s / external), battery backup switchover (VOUT up to 100 mA), CE gating (3 ns propagation), and power-fail warning (1.3 V PFI threshold) for embedded 5 V systems.

For engineers reviewing the ADM8691ARUZ datasheet, ADM8691ARUZ pinout, ADM8691ARUZ application, or ADM8691ARUZ equivalent, this page delivers verified functional roles, real-world timing behavior, battery switchover hysteresis (20 mV), CEOUT logic gating under brownout, and WDO status signaling - all critical for reliable system power sequencing and data retention design.

Technical Context

The ADM8691ARUZ integrates a precision 4.65 V reset comparator with 40 mV hysteresis, an internal oscillator selectable between 100 ms and 1.6 s watchdog periods (or externally adjustable via OSC IN/OSC SEL), and independent BATT ON, LOW LINE, and WDO outputs. Its dual-mode oscillator supports both fixed and capacitor-timed configurations.

It implements fast CEIN-to-CEOUT gating (3 ns delay) with automatic high-Z override during reset, battery switchover with 70 mV turn-on and 50 mV turn-off thresholds, and a dedicated 1.3 V power-fail comparator feeding PFO - all operating down to VCC = 1 V for guaranteed shutdown integrity.

Key Specifications

Pinout & Package

ADM8691ARUZ is housed in a 16-lead TSSOP package (4.4 mm × 5.0 mm, 0.65 mm pitch), optimized for space-constrained industrial and automotive PCB layouts.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MAX691ACPE+ and TPS3823-50DBVR, the ADM8691ARUZ uniquely combines adjustable watchdog timing, CE gating, and battery switchover in one 16-pin TSSOP - enabling single-chip data integrity protection for 5 V microprocessor systems without discrete support components.

Availability

ADM8691ARUZ is available at Aetrix Electronics and suitable for industrial PLC controllers, automotive infotainment units, medical handheld diagnostics, smart energy meters, and battery-backed data loggers requiring stable component supply across extended temperature ranges.

Supply support for ADM8691ARUZ 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 ADM8691ARUZ belongs to Analog Devices' microprocessor supervisory IC product line, engineered specifically to replace discrete reset + battery switch + watchdog solutions in 5 V embedded systems with guaranteed sub-1 V reset hold and integrated memory protection.

FAQ

What is the minimum VCC voltage at which ADM8691ARUZ guarantees RESET assertion?

The ADM8691ARUZ guarantees RESET assertion down to VCC = 1 V. This ensures the microprocessor remains held in reset during deep brownout conditions, preventing undefined operation or data corruption. The RESET output remains functional and actively driven even as VCC collapses, making ADM8691ARUZ suitable for systems requiring fail-safe shutdown behavior. This specification is validated across the full industrial temperature range (−40°C to +85°C).

How does the ADM8691ARUZ implement battery backup switchover, and what is its hysteresis?

The ADM8691ARUZ automatically switches VOUT between VCC and VBATT based on relative voltage levels: it connects VOUT to VBATT when VCC falls below VBATT − 70 mV (turn-on), and reconnects to VCC when VCC rises above VBATT + 50 mV (turn-off), yielding 20 mV hysteresis. This prevents chattering during slow supply decay. The internal 7 Ω MOSFET in battery mode draws only 0.4 μA, supporting multi-year backup with lithium coin cells or supercapacitors. ADM8691ARUZ also provides the BATT ON signal to drive external PNP transistors for >100 mA loads.

Can the reset pulse width and watchdog timeout of ADM8691ARUZ be adjusted, and how?

Yes. The ADM8691ARUZ supports adjustable reset pulse width (50 ms default) and watchdog timeout (100 ms / 1.6 s default) via two methods: (1) OSC SEL high/floating + OSC IN tied high (100 ms) or low (1.6 s); or (2) OSC SEL low + external capacitor (47 pF nominal) on OSC IN to set both parameters proportionally (e.g., 400 ms × C/47 pF for reset). An external clock (0–500 kHz) applied to OSC IN with OSC SEL low offers precise cycle-based timing. All configurations are validated in the ADM8691ARUZ datasheet Rev. C.

What is the function of CEIN and CEOUT pins on ADM8691ARUZ, and what is their propagation delay?

CEIN is the chip-enable input; CEOUT is its gated, buffered replica. When VCC is above 4.73 V, CEOUT follows CEIN with a guaranteed 3 ns propagation delay. When VCC drops below the reset threshold (~4.5 V), CEOUT is forced high regardless of CEIN state - blocking writes to battery-backed RAM or EEPROM. This hardware-enforced write protection prevents data corruption during power instability. The ADM8691ARUZ CEOUT output can directly drive standard CMOS inputs without pull-up resistors, and its 3 ns delay ensures timing-critical memory interfaces remain synchronized.

Does ADM8691ARUZ provide both active-low and active-high reset outputs, and how are they used?

Yes. ADM8691ARUZ provides two independent reset outputs: pin 15 (RESET) is active-low, and pin 16 (RESET) is active-high - the logical inverse. This dual-output architecture eliminates the need for external inverters when interfacing with microprocessors that require opposite reset polarity (e.g., ARM Cortex-M series vs. legacy 8051 derivatives). Both outputs share the same timing: 50 ms pulse width after VCC recovery or watchdog timeout, and both remain asserted down to VCC = 1 V. The ADM8691ARUZ datasheet confirms simultaneous operation and drive capability for direct CMOS loading.