Analog Devices Inc. ADM690SQ

Overview

ADM690SQ from Analog Devices is a precision microprocessor supervisory circuit in 8-pin plastic DIP (Q-8) package, providing power-on reset, battery backup switchover, watchdog timer (1.6 s nominal), 4.65 V reset threshold, and power-fail warning for +5 V systems. It asserts RESET down to 1 V VCC and delivers up to 100 mA from VOUT to CMOS RAM in industrial and extended-temperature embedded controllers.

For engineers reviewing the ADM690SQ datasheet, ADM690SQ pinout, ADM690SQ application, or ADM690SQ equivalent, this page delivers verified functional specifications, validated pin roles, confirmed thermal range (–55°C to +125°C), exact reset timing (50 ms), and real-world substitution guidance - all grounded in Analog Devices' official ADM690–ADM695 family documentation.

Technical Context

The ADM690SQ implements a fixed-function supervisory architecture with internal 4.65 V reset comparator (±40 mV hysteresis), non-adjustable 50 ms reset pulse width, and hardwired 1.6 s watchdog timeout period. Its battery switchover circuit uses dual PMOS switches (1.5 Ω normal mode, 20 Ω backup mode) to route VCC or VBATT to VOUT based on 70 mV/50 mV rising/falling differential thresholds.

It features a dedicated PFI/PFO comparator referenced to 1.3 V for early power-fail detection, CEIN/CEOUT gating with 5 ns propagation delay, and BATT ON output capable of sinking 35 mA to drive external PNP transistors - all operating within its –55°C to +125°C extended temperature range without configuration pins.

Key Specifications

Pinout & Package

ADM690SQ is housed in an 8-pin plastic DIP (Q-8) package with 0.3-inch body width and standard through-hole mounting. 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 MAX690CSA+ and TPS3823MPW, the ADM690SQ uniquely combines extended temperature operation, battery switchover, watchdog timer, and power-fail warning in a single 8-pin DIP - making it irreplaceable for mission-critical systems requiring full supervisory functionality across extreme environments.

Availability

ADM690SQ is available at Aetrix Electronics and suitable for automotive engine control units, industrial PLCs, aerospace data loggers, and military handheld radios requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for ADM690SQ 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 precision instrumentation, industrial automation, and aerospace markets since 1965.

The ADM690–ADM695 family was designed specifically for robust microprocessor system supervision - integrating reset, battery backup, watchdog, and power-fail detection into single-chip solutions for harsh-environment embedded control.

FAQ

What is the guaranteed reset voltage threshold for ADM690SQ?

The ADM690SQ has a guaranteed reset voltage threshold of 4.5 V minimum to 4.73 V maximum, with a typical value of 4.65 V. This specification is fully characterized over its –55°C to +125°C operating range and ensures compatibility with 5 V ±5% power supplies. The ADM690SQ reset comparator includes 40 mV hysteresis to prevent chatter during slow VCC transitions, and the RESET output remains active down to 1 V VCC - a critical feature for brownout resilience in the ADM690SQ design.

Does ADM690SQ support adjustable watchdog timeout or reset pulse width?

No, the ADM690SQ does not support adjustable watchdog timeout or reset pulse width. As a member of the base ADM690 series, it features fixed 1.6 s watchdog timeout and fixed 50 ms reset pulse width - unlike the ADM691/ADM693/ADM695 variants which offer OSC SEL and OSC IN pins for configuration. This fixed functionality simplifies design validation and reduces BOM complexity in applications where timing stability is prioritized over flexibility, and is explicitly documented in the ADM690SQ product selection guide and pin configuration tables.

What is the maximum continuous output current from VOUT on ADM690SQ?

The ADM690SQ delivers up to 100 mA continuously from its VOUT pin with a typical dropout voltage of 0.025 V at 1 mA and ≤0.5 V at 100 mA load. This capability is enabled by an internal 1.5 Ω PMOS switch in normal mode and is fully specified across the –55°C to +125°C temperature range. For loads exceeding 100 mA, the ADM690SQ datasheet recommends using the BATT ON output to drive an external PNP transistor - though note that BATT ON is not present on the ADM690SQ (only on ADM691/693/695), so external driver circuitry must be added separately when scaling current beyond 100 mA.

How does ADM690SQ handle battery backup switchover during power failure?

The ADM690SQ performs automatic battery backup switchover using a precision differential comparator that monitors VCC versus VBATT. Switchover occurs when VCC falls 50 mV below VBATT (power-down) or rises 70 mV above VBATT (power-up), providing 20 mV hysteresis to prevent oscillation. In backup mode, VOUT connects to VBATT via a 20 Ω MOSFET switch, sustaining CMOS RAM with ≤1 µA quiescent current. During this state, RESET goes low, LOW LINE goes low, PFO goes low, and WDI is internally disconnected - all behaviors confirmed in Table II of the ADM690SQ datasheet.

Is ADM690SQ pin-compatible with other devices in the ADM690–ADM695 family?

Yes, the ADM690SQ shares identical 8-pin Q-8 DIP pinout with ADM690AN, ADM690AQ, ADM692SQ, and ADM694SQ - all members of the 8-pin variant group. Pin functions (VCC, VBATT, VOUT, GND, RESET, WDI, PFI, PFO) are electrically and physically identical across these parts. However, functional differences exist: ADM692SQ uses 4.4 V reset threshold, ADM694SQ uses 200 ms reset pulse, and ADM690SQ is the only S-version part with 4.65 V/50 ms in the 8-pin footprint. This pin-compatibility enables drop-in replacement for temperature range upgrades without PCB revision.