Analog Devices Inc. ADM691AARN-REEL

Overview

ADM691AARN-REEL from Analog Devices is a microprocessor supervisory circuit integrating power-on reset, battery backup switchover, watchdog timer, chip enable gating, and power-fail detection. It features a 4.65 V ±3% reset threshold, 200 ms fixed reset timeout (adjustable), 1.6 s/100 ms selectable watchdog timeout, and supports VCC down to 1 V operation. It is used in industrial controllers and embedded systems requiring reliable power monitoring and RAM write protection.

For engineers reviewing the ADM691AARN-REEL datasheet, ADM691AARN-REEL pinout, ADM691AARN-REEL application, or ADM691AARN-REEL equivalent, key selection criteria include its dual-supply switchover capability (VCC/VBATT), open-drain RESET and complementary active-high RESET outputs, integrated CE gating with 6 ns propagation delay, and 1.25 V PFI comparator for early power-fail warning.

Technical Context

The ADM691AARN-REEL implements a precision bandgap-based voltage detector for 4.65 V reset threshold with 15 mV hysteresis, and uses an internal oscillator (or external clock/capacitor) to generate both reset timeout (200 ms typ) and watchdog timeout (1.6 s long / 100 ms short). Its battery switchover employs PMOS (VCC→VOUT, R_ON = 0.75 Ω) and NMOS (VBATT→VOUT, R_ON = 7 Ω) switches controlled by a comparator with 60 mV hysteresis.

Chip enable gating operates as a low-latency pass-through (CEIN→CEOUT) when VCC > reset threshold, but forces CEOUT high during reset or brownout - ensuring CMOS RAM write protection. The WDI input is three-level (high/mid/low), with automatic disable when floating (~1.6 V bias), and WDO provides asynchronous watchdog status independent of RESET timing.

Key Specifications

Pinout & Package

ADM691AARN-REEL is housed in a 16-pin narrow SOIC (R-16N) package, 7.5 mm × 10.3 mm, 1.27 mm pitch, RoHS-compliant, moisture sensitivity level 1.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MAX691ACPE+, ADM691AARN-REEL offers lower quiescent current and SOIC packaging; versus TPS3823MPW, it delivers full battery management and memory protection in one device - eliminating four discrete components in typical implementations.

Availability

ADM691AARN-REEL is available at Aetrix Electronics and suitable for industrial PLC controllers, automotive body control modules, and medical infusion pumps requiring stable component supply, long-term lifecycle support, and guaranteed traceable sourcing.

Supply support for ADM691AARN-REEL 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 ADM691AARN-REEL belongs to Analog Devices' microprocessor supervisory circuit family, designed specifically for robust power monitoring, battery-backed memory retention, and watchdog-based firmware validation in mission-critical embedded systems.

FAQ

What is the reset threshold voltage of the ADM691AARN-REEL?

The ADM691AARN-REEL has a guaranteed reset threshold of 4.65 V ±3%, with minimum and maximum limits of 4.5 V and 4.75 V respectively. This specification ensures compatibility with standard +5 V supplies operating within –5% to +10% tolerance. The threshold is implemented using a precision bandgap reference and remains stable across temperature (–40°C to +85°C) and supply variations. The ADM691AARN-REEL also includes 15 mV hysteresis to prevent chatter during slow-rising or noisy VCC conditions.

How does the ADM691AARN-REEL handle battery backup switchover?

The ADM691AARN-REEL automatically switches VOUT between VCC and VBATT based on voltage comparison and reset state. When VCC exceeds VBATT + 0.03 V and remains above 4.65 V, VCC is routed to VOUT via a 0.75 Ω PMOS switch. When VCC drops below VBATT – 0.03 V and falls below the reset threshold, VBATT is connected to VOUT through a 7 Ω NMOS switch. Switchover hysteresis is 60 mV, and battery standby current is as low as 0.04 µA - confirmed in battery backup mode per datasheet Figure 3.

Can the watchdog timeout period of the ADM691AARN-REEL be adjusted?

Yes, the ADM691AARN-REEL supports three watchdog timeout configurations: fixed 100 ms (OSC IN grounded), fixed 1.6 s (OSC IN and OSC SEL floating), or adjustable via external capacitor (OSC SEL grounded, COSC from OSC IN to GND) yielding T_WD = 600 × (C/47 pF) ms. An external clock may also be applied to OSC IN (with OSC SEL grounded) for T_WD = 1024/f_CLK. All modes are validated in Table II and Figure 9 of the official ADM691A datasheet.

What is the function of the CEIN and CEOUT pins on the ADM691AARN-REEL?

CEIN accepts the microprocessor's chip enable or write signal; CEOUT delivers a gated replica to CMOS RAM or EEPROM. When VCC is valid (>4.65 V), CEOUT follows CEIN with 6 ns propagation delay. During reset or brownout (VCC < 4.65 V), CEOUT is forced high - blocking write operations and preserving memory integrity. This behavior is specified in the "CE Gating and RAM Write Protection" section and verified in Figure 17 timing diagrams for ADM691AARN-REEL.

Does the ADM691AARN-REEL provide both active-low and active-high reset outputs?

Yes, the ADM691AARN-REEL provides two dedicated reset outputs: pin 15 (RESET) is open-drain active-low, and pin 16 (RESET) is active-high complementary. Both are asserted simultaneously during power-up, power-down, or brownout events. The active-high output eliminates the need for an external inverter in systems requiring high-active reset signals - a design feature explicitly documented in the "Power Fail Reset Output" section and functional block diagram (Figure 16) of the ADM691A datasheet.