Analog Devices Inc. ADM705AN

Overview

ADM705AN from Analog Devices is a low-cost microprocessor supervisory circuit designed for 5 V supply monitoring in embedded systems. It provides guaranteed active-low RESET output down to VCC = 1 V, 4.65 V precision reset threshold, 200 ms reset pulse width, and integrated watchdog timer with 1.60 sec timeout-enabling reliable power-up, brownout, and software stall detection in industrial controllers and instrumentation.

For engineers reviewing the ADM705AN datasheet, ADM705AN pinout, ADM705AN application, or ADM705AN equivalent, key selection considerations include its PDIP-8 package, TTL/CMOS-compatible manual reset input (MR), watchdog input (WDI) and output (WDO) functionality, and compatibility with 5 V microprocessor systems requiring fail-safe reset assertion during undervoltage or firmware lockup events.

Technical Context

The ADM705AN implements a precision voltage monitor with 4.65 V ±150 mV threshold and 40 mV hysteresis, ensuring clean reset assertion/deassertion during supply ramp-up and brownout recovery. Its internal 1.60 sec watchdog timer clears on any WDI transition (high-to-low or low-to-high) and forces WDO low on timeout or VCC dropout below 4.65 V.

A dedicated 1.25 V power-fail comparator accepts external voltage via PFI to generate early warning (PFO) of supply collapse or battery depletion. The MR input features internal 250 µA pull-up and hardware debouncing, supporting direct connection to switches or logic without external RC networks.

Key Specifications

Pinout & Package

ADM705AN is housed in an 8-lead narrow-body plastic dual-in-line package (PDIP, N-8), compliant with JEDEC MS-001-BA, with 0.300-inch body width and 0.100-inch lead pitch. Pin 1 is marked with a notch or dot; leads are straight and through-hole mountable.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MAX705CPA+, ADM705AN reduces BOM count via internal MR pull-up and offers superior brownout immunity with guaranteed 1 V operation; versus TPS3808G33DBVR, ADM705AN delivers full-feature supervision (watchdog, PFI/PFO, dual reset polarity support) essential for robust 5 V microprocessor systems.

Availability

ADM705AN is available at Aetrix Electronics and suitable for industrial PLCs, medical diagnostic instruments, telecom base station management units, and automotive body control modules requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for ADM705AN 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, headquartered in Norwood, MA, serving industrial, automotive, communications, and healthcare markets.

The ADM705 series belongs to Analog Devices' microprocessor supervisory product line, engineered specifically for robust, low-power, multi-function reset and system health monitoring in 5 V embedded systems with demanding reliability requirements.

FAQ

What is the reset threshold voltage of the ADM705AN?

The ADM705AN has a precision reset threshold of 4.65 V, with a tolerance of ±150 mV and 40 mV hysteresis. This value is factory-trimmed and guaranteed over the full −40°C to +85°C industrial temperature range. The threshold ensures reliable reset assertion before 5 V system logic becomes unstable, and its hysteresis prevents chatter during slow supply ramps. The ADM705AN's 4.65 V threshold distinguishes it from the ADM706AN (4.40 V) and aligns with standard TTL-compatible reset margins.

Does the ADM705AN support watchdog functionality?

Yes, the ADM705AN includes a fully integrated watchdog timer with a nominal timeout period of 1.60 seconds. The timer resets on any transition (high-to-low or low-to-high) at the WDI pin and forces the WDO output low upon timeout. WDO can be connected to the MR input to generate a system reset, or used independently as a nonmaskable interrupt source. Watchdog operation is disabled when WDI is left floating, allowing flexible configuration in systems that do not require firmware supervision.

Can the ADM705AN monitor a secondary power supply?

Yes, the ADM705AN provides a dedicated power-fail comparator with a 1.25 V internal reference and PFI/PFO pins. By connecting an external resistor divider from a secondary supply (e.g., 3.3 V or 2.5 V) to PFI, the device generates an active-low PFO signal when that supply drops below the programmed threshold. This enables early warning of auxiliary rail collapse, battery depletion, or preregulator failure-without requiring additional comparators or supervisors. The PFI input draws only ±25 nA, minimizing loading on the monitored supply.

What package type is used for the ADM705AN?

The ADM705AN is supplied in an 8-lead narrow-body plastic dual-in-line package (PDIP, N-8), per JEDEC MS-001-BA. It features a 0.300-inch body width, 0.100-inch lead pitch, and through-hole mounting. This package is pin-compatible with industry-standard supervisory ICs including the MAX705 series and supports hand-soldering, wave soldering, and automated assembly. The N-8 package provides robust thermal performance and mechanical stability for industrial environments.

How does the ADM705AN handle manual reset inputs?

The ADM705AN's MR (Manual Reset) input is TTL/CMOS-compatible, internally debounced, and features a 250 µA pull-up current-eliminating the need for external pull-up resistors when interfacing with mechanical switches or open-drain logic. Driving MR below 0.8 V asserts RESET for 200 ms. The input also supports logic-level reset signals from other ICs. MR-to-RESET propagation delay is 250 ns, ensuring fast, deterministic response. This design simplifies board layout and improves reliability in noisy industrial settings.