Analog Devices Inc. ADM8690AN

Overview

ADM8690AN from Analog Devices is an 8-lead PDIP microprocessor supervisory circuit providing power-on/brownout reset, battery backup switchover, watchdog timer (fixed 1.6 sec), and 1.3 V power-fail detection. It asserts active-low RESET down to VCC = 1 V, delivers up to 100 mA at VOUT with 0.7 Ω on-resistance, and consumes only 0.7 mW typical. It is used in embedded controllers and industrial instrumentation requiring reliable power monitoring and nonvolatile memory retention.

For engineers reviewing the ADM8690AN datasheet, ADM8690AN pinout, ADM8690AN application, or ADM8690AN equivalent, key selection criteria include its fixed 4.65 V reset threshold, guaranteed 50 ms reset pulse width, 1.6 sec watchdog timeout, battery switchover hysteresis of 20 mV, and compatibility with 5 V ±5% supplies - all validated for industrial temperature range (−40°C to +85°C).

Technical Context

The ADM8690AN integrates a precision 4.65 V reset comparator with 40 mV hysteresis, a dedicated 1.3 V power-fail comparator (PFI/PFO), and a fixed-frequency watchdog timer with 1.6 sec timeout. Its internal PMOS switch enables automatic VCC/VBATT selection to VOUT, maintaining CMOS RAM supply during main power loss.

RESET remains functional down to 1 V VCC, ensuring deterministic shutdown; the BATT ON signal is absent (only present on ADM8691/ADM8695), confirming ADM8690AN's simplified 8-pin architecture without CE gating or WDO output. All timing and thresholds are factory-trimmed and specified over full industrial temperature range.

Key Specifications

Pinout & Package

ADM8690AN is housed in an 8-lead plastic DIP (PDIP) package with 0.3 inch body width and standard through-hole footprint. Pin spacing is 0.1 inch, compatible with legacy PCB layouts and socket-based prototyping.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MAX690CPA+ and TPS3823-50DBVR, ADM8690AN uniquely integrates battery switchover, watchdog, and power-fail detection in a single 8-pin PDIP - reducing component count and enabling compact, self-contained supervision for memory-critical 5 V systems.

Availability

ADM8690AN is available at Aetrix Electronics and suitable for industrial controllers, automotive body electronics, medical instrumentation, and point-of-sale terminals requiring stable component supply and long-term obsolescence management.

Supply support for ADM8690AN 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 ADM8690AN belongs to Analog Devices' microprocessor supervisory IC family, designed specifically to replace legacy ADM690/ADM691 and MAX690-series devices with enhanced accuracy, lower power, and integrated battery management for 5 V embedded systems.

FAQ

What is the minimum VCC voltage at which ADM8690AN guarantees RESET functionality?

ADM8690AN guarantees RESET output operation down to VCC = 1 V. At this voltage, RESET remains functional with a sink capability of 10 μA and output voltage ≤20 mV. This ensures the microprocessor stays held in reset even during severe brownout conditions where other supervisors would release prematurely - a critical feature for fail-safe operation in industrial and automotive environments where ADM8690AN is deployed.

Does ADM8690AN support adjustable reset timeout or watchdog period?

No, ADM8690AN does not support adjustable timing. Its reset pulse width is fixed at 50 ms and watchdog timeout is fixed at 1.6 sec. Unlike ADM8691/ADM8695, ADM8690AN omits OSC SEL and OSC IN pins and contains no external capacitor or clock interface. This simplifies design for applications requiring predictable, unchangeable supervision timing - such as legacy systems migrating from ADM690 or MAX690 where timing consistency is mandatory.

Can ADM8690AN drive CMOS RAM directly without external components?

Yes, ADM8690AN can drive CMOS RAM directly via its VOUT pin, delivering up to 100 mA with ≤0.2 V dropout at full load. Its internal 0.7 Ω PMOS switch eliminates the need for external pass transistors or diodes in most designs. A 0.1 μF bypass capacitor on VOUT is recommended to handle RAM write-current transients. This direct-drive capability is a core design feature of ADM8690AN, distinguishing it from basic reset-only supervisors that lack integrated power switching.

What is the function of the PFI and PFO pins on ADM8690AN?

PFI (Pin 5) is the noninverting input to a dedicated 1.3 V comparator; when voltage at PFI falls below 1.25–1.35 V, PFO (Pin 6) goes low. PFO is an active-low, open-drain output used to trigger microprocessor interrupts for early power-fail warning - enabling data save operations before VCC collapse. This dual-threshold supervision (4.65 V for RESET, 1.3 V for PFO) allows ADM8690AN to provide both system reset and predictive power-loss signaling in a single IC.

Is ADM8690AN pin-compatible with the ADM690 or MAX690?

Yes, ADM8690AN is a direct pin-compatible upgrade for ADM690AN and MAX690CPA+. All share identical 8-pin PDIP pinout (VBATT, VOUT, VCC, GND, PFI, PFO, WDI, RESET), same reset threshold (4.65 V), and compatible timing. ADM8690AN improves upon them with lower supply current (200 μA vs. ~500 μA), guaranteed 1 V RESET operation, tighter threshold tolerance, and integrated battery switchover - making it a drop-in replacement that enhances reliability without PCB changes.