Analog Devices Inc. ADM708AR

Overview

ADM708AR from Analog Devices is a low-cost microprocessor supervisory circuit with 4.40 V reset threshold, 200 ms reset pulse width, and active-high RESET output-designed for 5 V supply monitoring in embedded controllers and industrial instrumentation where brownout immunity and manual reset debouncing are required.

For engineers reviewing the ADM708AR datasheet, ADM708AR pinout, ADM708AR application, or ADM708AR equivalent, key selection criteria include guaranteed RESET validity down to 1 V VCC, precision 1.25 V power-fail comparator input (PFI), TTL/CMOS-compatible manual reset (MR), and SOIC-8 packaging for space-constrained PCB layouts.

Technical Context

The ADM708AR implements a fixed-threshold voltage monitor with 4.40 V ±0.15 V hysteresis and generates an active-high RESET signal that remains asserted for 200 ms after VCC rises above threshold or MR deasserts. It lacks watchdog functionality but includes a dedicated PFI/PFO pair for external supply monitoring.

Its internal 250 µA MR pull-up current enables direct switch interfacing without external biasing, while the 190 µA quiescent current supports low-power system design. The device operates across −40°C to +85°C and guarantees valid RESET output down to VCC = 1 V.

Key Specifications

Pinout & Package

ADM708AR is housed in an 8-lead SOIC_N (R-8) package per JEDEC MS-012-AA, with 1.27 mm lead pitch, 4.90 mm × 3.90 mm body, and 1.75 mm height. Pin 1 is marked by a beveled corner.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MAX708R and TPS3808G33, the ADM708AR uniquely combines fixed 4.40 V supervision, active-high/active-low RESET outputs, and integrated PFI/PFO in SOIC-8 - making it optimal for cost-sensitive 5 V systems requiring robust brownout response and external supply monitoring without watchdog overhead.

Availability

ADM708AR is available at Aetrix Electronics and suitable for industrial PLCs, medical diagnostic controllers, telecom remote terminals, automotive body control modules, and intelligent instrumentation requiring stable component supply with full RoHS compliance and long-term lifecycle support.

Supply support for ADM708AR 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 ADM705–ADM708 family was designed specifically for reliable, low-cost microprocessor supervision in 5 V systems - emphasizing brownout immunity, manual reset integration, and power-fail warning without requiring external components.

FAQ

What is the reset threshold voltage for the ADM708AR?

The ADM708AR has a nominal reset threshold of 4.40 V with ±0.15 V tolerance over temperature and supply variation. This value is factory-trimmed and specified in Table 1 of the Rev. H datasheet. The ADM708AR uses this threshold to assert RESET when VCC falls below 4.40 V and maintain it until VCC rises above the threshold plus hysteresis (40 mV). This ensures clean power-on reset behavior in 5 V systems.

Does the ADM708AR include a watchdog timer function?

No, the ADM708AR does not include a watchdog timer. Unlike the ADM705/ADM706 variants, the ADM708AR omits the WDI and WDO pins and associated timing circuitry. Its functional block diagram (Figure 2) confirms absence of watchdog logic. The ADM708AR focuses exclusively on voltage supervision, manual reset, and power-fail detection - making it simpler and lower in quiescent current than watchdog-equipped versions.

How does the ADM708AR handle power-fail detection?

The ADM708AR uses its PFI (Power Fail Input) pin connected to an internal 1.25 V comparator. When the voltage at PFI drops below 1.25 V, the PFO (Power Fail Output) pin goes low, signaling impending supply collapse. This allows the host microcontroller to initiate graceful shutdown. The ADM708AR datasheet specifies PFI threshold as 1.25 V ±0.05 V and recommends using a resistive divider from the monitored supply to set the trip point.

What are the two RESET outputs on the ADM708AR used for?

The ADM708AR provides both RESET (pin 7, active-high) and RESET (pin 8, active-low) outputs. The active-high output drives high during reset assertion and is compatible with MCUs requiring high-true reset logic. The active-low output is open-drain and sinks current when asserted, enabling wired-OR connection with other reset sources. This dual-output architecture allows the ADM708AR to interface with heterogeneous reset domains in complex systems without level-shifting.

Is the ADM708AR pin-compatible with the MAX708 series?

The ADM708AR is functionally and pin-compatible with the MAX708R in SOIC-8 package, sharing identical pin assignments for VCC, GND, MR, PFI, PFO, RESET, RESET, and NC. However, the MAX708R includes a watchdog timer (WDI/WDO) not present in the ADM708AR. While both meet 4.40 V reset threshold and 200 ms pulse width specs, the ADM708AR's lack of watchdog circuitry results in lower quiescent current (190 µA vs. ~250 µA for MAX708R).