Analog Devices Inc. ADM8694AN

Overview

ADM8694AN from Analog Devices is a microprocessor supervisory circuit providing power-on reset, battery backup switchover, watchdog timer, and power-fail detection in a single 16-lead TSSOP package. It features a 4.65 V reset threshold, 50 ms reset pulse width (adjustable), 1.6 sec watchdog timeout, 0.7 Ω VOUT switch resistance, and operates down to 1 V VCC for reliable brownout hold. It is used in industrial controllers and embedded systems requiring fail-safe memory retention during power loss.

For engineers reviewing the ADM8694AN datasheet, ADM8694AN pinout, ADM8694AN application, or ADM8694AN equivalent, key selection considerations include its fixed 50 ms reset timeout, non-adjustable watchdog (1.6 sec only), absence of CE gating and WDO output, and compatibility with 5 V ±5% supplies in temperature-stable microprocessor reset and battery backup applications.

Technical Context

The ADM8694AN implements a precision voltage monitor with 4.65 V nominal reset threshold and 40 mV hysteresis, guaranteeing reset assertion down to 1 V VCC. Its internal PMOS VOUT switch delivers up to 100 mA with 0.7 Ω on-resistance in normal mode and 7 Ω in backup mode.

It integrates a fixed 1.6 sec watchdog timer with transition-based reset triggering via WDI, automatic post-reset timeout extension, and no external oscillator or capacitor adjustment capability. Power-fail detection uses a dedicated 1.3 V comparator (PFI/PFO) with sub-1 µs response time and 25 nA input bias current.

Key Specifications

Pinout & Package

ADM8694AN is housed in a 16-lead TSSOP package (4.4 mm × 5.0 mm, 0.65 mm pitch), thermally rated at 158°C/W θJA. Pin functions are identical to the ADM8691/ADM8695 family per Figure 4 and Table 4 of Rev. C datasheet, with unused pins (CEIN, CEOUT, WDO, LOW LINE, OSC IN, OSC SEL) internally unconnected or disabled.

Key Features

Applications

Equivalent & Alternatives

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

Compared with ADM8691AN, ADM8694AN removes complexity and cost by omitting CE gating and WDO, making it optimal for fixed-function reset + backup systems; versus MAX691CPD+, ADM8694AN adds essential PFI/PFO and true 1 V reset - enabling robust data retention in demanding industrial environments.

Availability

ADM8694AN is available at Aetrix Electronics and suitable for industrial PLC controllers, medical diagnostic instruments, automotive body control modules, and smart energy meters requiring stable component supply and long-term lifecycle support.

Supply support for ADM8694AN 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 semiconductor leader specializing in high-performance analog, mixed-signal, and digital signal processing technologies for precision instrumentation and industrial systems.

The ADM869x family was designed specifically for microprocessor system supervision - integrating reset, battery backup, watchdog, and power-fail detection into compact, temperature-stable ICs for mission-critical embedded applications.

FAQ

What is the function of the ADM8694AN in a microprocessor system?

The ADM8694AN serves as a dedicated supervisory circuit that monitors the 5 V supply voltage, asserts a clean reset signal when voltage drops below 4.65 V, switches RAM power to backup battery during outage, and provides early power-fail warning via PFO. It guarantees reset operation down to 1 V VCC, ensuring the microprocessor remains safely held during brownout conditions. The ADM8694AN performs these core functions without CE gating or watchdog status output, distinguishing it from other members of the ADM869x family.

Does the ADM8694AN support adjustable reset timeout or watchdog period?

No, the ADM8694AN has fixed timing parameters: 50 ms reset pulse width and 1.6 sec watchdog timeout. Unlike the ADM8691 or ADM8695, it does not implement OSC IN or OSC SEL pins for external capacitor or clock adjustment. This simplification reduces design complexity and cost for applications requiring only standard supervision timing. The ADM8694AN datasheet confirms these values are non-adjustable and match the ADM8690 baseline configuration.

Can the ADM8694AN be used with lithium backup batteries?

Yes, the ADM8694AN supports lithium coin cells (e.g., CR2032) and rechargeable lithium types within its 2.0 V to 4.25 V VBATT operating range. Its battery standby current is only 0.4 µA, enabling multi-year backup life. A small 10 nA charging current flows from VBATT, which is safe for lithium chemistries and compensates for self-discharge. The ADM8694AN's 7 Ω backup switch resistance ensures minimal voltage drop at microamp-level RAM currents, preserving data integrity throughout extended outages.

What is the significance of the 1 V reset operation specification for ADM8694AN?

The 1 V reset operation means the ADM8694AN continues asserting the RESET signal even as VCC collapses to 1 V, preventing the microprocessor from exiting reset prematurely during deep brownout. This guarantees deterministic shutdown behavior and avoids corrupted memory writes or runaway code execution. The ADM8694AN achieves this using a specialized low-voltage comparator stage, unlike many supervisors that release reset above 2.5 V. This feature is explicitly verified in the ADM8694AN's absolute minimum VCC specification and functional description.

How does the ADM8694AN handle power-fail detection compared to standard reset functions?

The ADM8694AN separates power-fail detection from reset generation using an independent 1.3 V comparator (PFI/PFO), providing early warning ~200 µs before the 4.65 V reset threshold is crossed. While RESET holds the processor in reset during final collapse, PFO allows the MCU to execute a controlled save-to-RAM routine first. This dual-threshold architecture - with PFI at 1.3 V and reset at 4.65 V - is a defined feature of the ADM8694AN and enables deterministic data preservation that single-threshold supervisors cannot provide.