Analog Devices Inc. ADM8691AN

Overview

ADM8691AN from Analog Devices is a 16-lead TSSOP microprocessor supervisory circuit providing precision reset generation (50 ms or adjustable), 4.65 V VCC monitoring, watchdog timeout selection (100 ms/1.6 s/adjustable), automatic battery backup switchover, and CE gating for RAM write protection. It operates across −40°C to +85°C and supports 5 V systems with brownout immunity down to 1 V.

For engineers reviewing the ADM8691AN datasheet, ADM8691AN pinout, ADM8691AN application, or ADM8691AN equivalent, this page delivers verified functional roles, real-world timing behavior, battery switchover thresholds, CE propagation delay (3 ns), and design-meaningful parameter values - all confirmed from Analog Devices Rev. C datasheet.

Technical Context

The ADM8691AN integrates a precision 4.65 V reset threshold comparator with 40 mV hysteresis, an internal oscillator selectable between 100 ms and 1.6 s watchdog periods (or externally adjustable via OSC IN), and dual-mode battery switchover logic that activates at VCC − VBATT = 70 mV (rising) and 50 mV (falling), with 20 mV hysteresis.

Its CEIN-to-CEOUT path provides 3 ns propagation delay with active-high gating: CEOUT tracks CEIN only when VCC ≥ 4.65 V; below threshold, CEOUT is forced high to prevent writes to battery-backed RAM. The WDO output asserts low on watchdog timeout and resets on next WDI transition or LOW LINE assertion.

Key Specifications

Pinout & Package

ADM8691AN is housed in a 16-lead TSSOP package (4.4 mm × 5.0 mm, 0.65 mm pitch), RoHS-compliant and rated for industrial temperature range (−40°C to +85°C).

Key Features

Applications

Equivalent & Alternatives

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

Compared with MAX691ACPE+ and TPS3823MPW, the ADM8691AN uniquely integrates battery switchover, CE gating, and dual-mode watchdog in a single 16-pin TSSOP-enabling compact, fail-safe 5 V microprocessor systems without supplemental ICs.

Availability

ADM8691AN is available at Aetrix Electronics and suitable for industrial PLC controllers, automotive infotainment head units, medical patient monitors, and network routers requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for ADM8691AN 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 ADM8691AN belongs to Analog Devices' microprocessor supervisory product line, engineered specifically for robust power monitoring, battery-backed memory protection, and deterministic reset sequencing in mission-critical 5 V embedded systems.

FAQ

What is the minimum VCC voltage at which ADM8691AN guarantees RESET assertion?

The ADM8691AN guarantees RESET assertion down to VCC = 1 V. This ensures the microprocessor remains held in reset during deep brownout conditions where other supervisors lose functionality. The RESET output remains valid and actively driven even at this ultra-low supply voltage, enabling reliable system shutdown sequencing in harsh electrical environments.

How does the ADM8691AN handle battery switchover hysteresis, and why is it critical?

The ADM8691AN uses 20 mV hysteresis in its battery switchover circuit: switchover occurs at VCC − VBATT = 70 mV on rising VCC and 50 mV on falling VCC. This prevents rapid toggling when VCC decays slowly near VBATT voltage-ensuring stable VOUT delivery to RAM during marginal power conditions and avoiding data corruption from supply chatter.

Can the ADM8691AN's watchdog timer be disabled, and how?

Yes, the ADM8691AN watchdog timer can be disabled by leaving the WDI pin floating or driving it to midsupply (~2.5 V). In either state, the internal watchdog circuit halts timing, and WDO remains high. This allows safe deactivation during debug or bootloader phases without hardware modification-verified in Analog Devices Rev. C datasheet Section "Watchdog Timer RESET".

What is the purpose of the CEIN and CEOUT pins on the ADM8691AN, and how do they protect memory?

The CEIN and CEOUT pins implement hardware-enforced write protection: CEOUT replicates CEIN only when VCC ≥ 4.65 V; below threshold, CEOUT is forced high to disable chip enable. This blocks writes to battery-backed RAM during brownout-preventing partial writes and data corruption. The 3 ns propagation delay ensures protection engages before supply collapse affects memory timing margins.

Does the ADM8691AN support both active-high and active-low reset outputs, and how are they used?

Yes, the ADM8691AN provides both RESET (Pin 15, active-low) and RESET (Pin 16, active-high) outputs. The active-low RESET drives standard microprocessor reset inputs, while the complementary active-high RESET serves processors requiring non-inverted reset signals-eliminating need for external inverters and reducing BOM count and layout complexity in mixed-architecture designs.