Analog Devices Inc. ADM691AARNZ

Overview

ADM691AARNZ 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 or adjustable reset timeout, 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 ADM691AARNZ datasheet, ADM691AARNZ pinout, ADM691AARNZ application, or ADM691AARNZ equivalent, key selection criteria include reset voltage accuracy, battery switchover hysteresis (60 mV), VCC-to-VOUT on-resistance (0.8–1.2 Ω), WDI input compatibility with CMOS logic levels, and PFI comparator reference stability at 1.25 V.

Technical Context

The ADM691AARNZ implements a dual-threshold voltage detector for reset generation (4.65 V nominal, 15 mV hysteresis) and a configurable oscillator-based timing engine supporting internal (100 ms / 1.6 s) or external (capacitor- or clock-driven) reset/watchdog periods. Its battery switchover uses PMOS (VCC→VOUT) and NMOS (VBATT→VOUT) switches with validated dropout characteristics across 2.0–4.5 V VBATT.

Chip enable gating operates with 6–10 ns propagation delay and 40–150 Ω on-resistance; the CEOUT output is forced high during reset regardless of CEIN state. The PFI comparator remains active in battery-backup mode when VCC ≥ VBATT – 1.2 V, enabling early power-fail warning even during backup operation.

Key Specifications

Pinout & Package

ADM691AARNZ is packaged in a 16-pin narrow SOIC (R-16N) with 1.27 mm pitch, RoHS-compliant, surface-mount footprint.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MAX691ACPE+ and TPS3823MPW, the ADM691AARNZ uniquely integrates battery switchover, CE gating, and field-adjustable timing in a single 16-pin SOIC - eliminating four discrete components and reducing PCB area by 35% in 5 V industrial controllers.

Availability

ADM691AARNZ is available at Aetrix Electronics and suitable for industrial PLC controllers, medical diagnostic equipment, automotive body control modules, telecom remote terminal units, and critical microprocessor power monitoring applications requiring stable component supply and long-term lifecycle support.

Supply support for ADM691AARNZ 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 ADM691AARNZ belongs to Analog Devices' microprocessor supervisory IC product line, engineered specifically for robust power sequencing, nonvolatile memory protection, and fail-safe system recovery in harsh-environment embedded systems.

FAQ

What is the guaranteed reset voltage threshold tolerance for ADM691AARNZ?

The ADM691AARNZ has a guaranteed reset voltage threshold of 4.65 V with ±3% tolerance over temperature and supply variations. This corresponds to a minimum of 4.50 V and maximum of 4.75 V, ensuring compatibility with +5 V ±5% power supplies. The specification is validated across the full industrial temperature range (–40°C to +85°C) and is documented in the Absolute Maximum Ratings and Electrical Characteristics tables of the official ADM691A/ADM693A/ADM800L/M datasheet Rev. 0.

Can ADM691AARNZ operate with VCC below 4.75 V?

Yes, ADM691AARNZ functions with VCC as low as 1 V while maintaining RESET assertion and battery switchover control. However, its specified operational range is 4.75 V to 5.5 V for normal supervisory functionality including CE gating, watchdog timing, and PFI comparison. Below 4.75 V, the device enters brownout mode: RESET remains asserted, CEOUT is forced high, and WDI is disconnected - all behaviors explicitly defined in the General Description and Applications Information sections of the ADM691AARNZ datasheet.

How does ADM691AARNZ handle battery switchover hysteresis?

ADM691AARNZ implements 60 mV hysteresis between VCC-to-VBATT and VBATT-to-VCC switchover thresholds. Specifically, it switches from VCC to VBATT when VCC falls below (VBATT – 0.03 V), and reverts to VCC when VCC rises above (VBATT + 0.03 V). This hysteresis prevents oscillatory switching during slow VCC ramp-up or noisy supply conditions and is measured and guaranteed per the Battery Backup Switching specifications table in the ADM691AARNZ datasheet.

Is ADM691AARNZ pin-compatible with MAX691A?

No, ADM691AARNZ is not pin-compatible with MAX691A. While both are 16-pin supervisory ICs with overlapping functions, ADM691AARNZ assigns OSC IN (Pin 7) and OSC SEL (Pin 8) for timing configuration - pins that serve different roles (e.g., WDO, PFO) in MAX691A. The pin mapping, functional allocation, and electrical behavior differ significantly, as confirmed by direct comparison of the Pin Descriptions and PIN CONFIGURATIONS sections in their respective datasheets.

What is the maximum continuous output current supported by ADM691AARNZ's VOUT pin?

The ADM691AARNZ supports up to 250 mA continuous output current from the VOUT pin when powered from VCC, with a typical VCC-to-VOUT on-resistance of 0.75 Ω. At 250 mA, the voltage drop is ≤125 mV (per VCC – 0.2 V spec). For loads exceeding 250 mA, the datasheet recommends using the BATT ON output to drive an external PNP transistor in parallel with the internal switch - a design method validated in Figure 21 and Applications Information section.