Analog Devices Inc. ADM691AARUZ

Overview

ADM691AARUZ 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, automatic VCC/VBATT switching to VOUT (250 mA max), and 1.25 V PFI comparator. It is used in industrial controllers and embedded systems requiring reliable power monitoring and RAM write protection during brownouts.

For engineers reviewing the ADM691AARUZ datasheet, ADM691AARUZ pinout, ADM691AARUZ application, or ADM691AARUZ equivalent, key selection criteria include reset voltage accuracy (±3%), battery switchover hysteresis (60 mV), CEOUT propagation delay (10 ns max), WDI input threshold compatibility (0.75×VCC logic high), and TSSOP-16 package thermal performance (θJA = 158°C/W).

Technical Context

The ADM691AARUZ implements a dual-supply switchover architecture using internal PMOS (VCC→VOUT, RON ≈ 0.75 Ω) and NMOS (VBATT→VOUT, RON ≈ 7 Ω) switches, enabling seamless transition between main supply and backup battery at VCC as low as 1 V. Its reset generator uses an internal oscillator with fixed 200 ms timeout or external capacitor/clock adjustment.

The watchdog timer employs a transition detector on WDI with configurable long (1.6 s) or short (100 ms) timeout periods, and includes automatic disable during reset assertion. The CE gating circuit forces CEOUT high when VCC falls below reset threshold-ensuring CMOS RAM write protection independent of CEIN state.

Key Specifications

Pinout & Package

ADM691AARUZ is housed in a 16-lead TSSOP (RU-16) package, 5.0 mm × 4.4 mm × 1.2 mm, with 0.65 mm lead pitch and exposed pad for thermal enhancement. Pin 1 is marked by a dot; pin numbering follows standard counter-clockwise convention from top-left corner.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MAX691ACPE+, ADM691AARUZ offers 3.5× lower active current and TSSOP packaging; compared with TPS3823MPW, it integrates five supervisory functions in one RU-16 package-reducing BOM count, board area, and validation effort for full-featured µP supervision.

Availability

ADM691AARUZ is available at Aetrix Electronics and suitable for industrial PLC controllers, automotive telematics modules, and medical infusion pumps requiring stable component supply across extended temperature ranges (–40°C to +85°C) and long production lifecycles.

Supply support for ADM691AARUZ 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, Inc. is a global leader in high-performance analog, mixed-signal, and digital signal processing semiconductors, headquartered in Norwood, MA.

The ADM691AARUZ belongs to Analog Devices' microprocessor supervisory circuit family, designed specifically to consolidate power monitoring, battery backup, watchdog, and memory protection functions into a single IC for space- and reliability-critical embedded systems.

FAQ

What is the guaranteed reset voltage threshold tolerance for ADM691AARUZ?

The ADM691AARUZ has a guaranteed reset voltage threshold of 4.65 V with ±3% tolerance over temperature (–40°C to +85°C), meaning the actual trip point falls between 4.50 V and 4.75 V. This specification ensures reliable reset assertion for +5 V ±5% power supplies. The ADM691AARUZ datasheet confirms this range under "Reset Voltage Threshold" in the Electrical Characteristics table.

Can ADM691AARUZ operate with VCC as low as 1 V, and what functions remain active?

Yes, ADM691AARUZ remains fully operational with VCC as low as 1 V. During this condition, the RESET output stays asserted low, the internal switchover circuit connects VBATT to VOUT, and the BATT ON output goes high. However, the watchdog timer and CE gating are disabled below VCC = 1 V, and the PFI comparator remains active only if VCC ≥ VBATT – 1.2 V. These behaviors are documented in the "GENERAL DESCRIPTION" and Table III of the ADM691AARUZ datasheet.

How does the ADM691AARUZ implement battery switchover hysteresis, and what is its value?

The ADM691AARUZ implements battery switchover hysteresis via internal comparator design that sets distinct thresholds for power-up (VBATT + 0.03 V) and power-down (VBATT – 0.03 V), resulting in a total hysteresis of 60 mV. This prevents oscillation during slow VCC transitions near the switchover point. The value is specified in the "Battery Switchover Threshold" section of the ADM691AARUZ datasheet and verified in Figure 5 and Table I.

Is ADM691AARUZ pin-compatible with the MAX691A family, and what are the key functional differences?

ADM691AARUZ is functionally compatible but not fully pin-compatible with MAX691A in SOIC or DIP packages due to different pin 16 assignment: ADM691AARUZ uses pin 16 as RESET (active-high open-drain), while MAX691A uses pin 16 as GND. Additionally, ADM691AARUZ adds adjustable watchdog timing via OSC IN/OSC SEL and improved battery standby current (0.04 µA vs. 20 µA). These distinctions are confirmed in the "PIN DESCRIPTIONS" and "ORDERING GUIDE" sections of the ADM691AARUZ datasheet.

What is the maximum continuous output current ADM691AARUZ can deliver from VOUT when powered by VCC?

The ADM691AARUZ delivers up to 250 mA continuously from VOUT when powered by VCC, with a typical VCC-to-VOUT on-resistance of 0.75 Ω. At 250 mA, the voltage drop is ≤300 mV (VCC – 0.3 V), ensuring sufficient headroom for downstream logic. This rating is validated in the "BATTERY BACKUP SWITCHING" section of the ADM691AARUZ datasheet and supported by Figure 6 showing VCC-to-VOUT voltage drop vs. current.