Analog Devices Inc. ADM691AARWZ

Overview

ADM691AARWZ 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, VCC-to-VOUT on-resistance of 0.75 Ω (typ), and operates down to 1 V VCC. It is used in industrial controllers and embedded systems requiring reliable power monitoring and RAM write protection.

For engineers reviewing the ADM691AARWZ datasheet, ADM691AARWZ pinout, ADM691AARWZ application, or ADM691AARWZ equivalent, key selection criteria include its precise 4.65 V reset threshold compatibility with +5 V ±5% supplies, battery switchover hysteresis of 60 mV, low 100 µA standby current, and dual RESET/RESET outputs supporting both active-low and active-high microprocessor interfaces.

Technical Context

The ADM691AARWZ implements a dual-threshold voltage detector for reset generation, with guaranteed 4.5 V min / 4.75 V max trip points and 15 mV hysteresis. Its internal oscillator supports fixed (200 ms / 1.6 s) or capacitor-adjustable timing via OSC IN, while OSC SEL selects between internal and external clock sources.

Battery switchover uses PMOS (VCC→VOUT) and NMOS (VBATT→VOUT) switches with validated 0.75 Ω and 7 Ω on-resistances respectively; CEOUT provides sub-10 ns propagation delay gating of RAM chip enables, and the 1.25 V PFI comparator enables early power-fail warning with 25 µs response delay.

Key Specifications

Pinout & Package

ADM691AARWZ is packaged in a 16-lead wide-body SOIC (R-16W), measuring 10.3 mm × 7.5 mm × 2.35 mm, with standard 1.27 mm pitch and gull-wing leads. 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 MAX691ACPE+, ADM691AARWZ offers 2.5× lower standby current and field-adjustable timing; compared with TPS3823MPW, it integrates battery switchover, CE gating, and PFI/PFO - eliminating ≥4 discrete components and reducing BOM cost by $0.32 in volume production.

Availability

ADM691AARWZ is available at Aetrix Electronics and suitable for industrial controllers, automotive body electronics, medical infusion pumps, and point-of-sale terminals requiring stable component supply across extended temperature ranges and long product lifecycles.

Supply support for ADM691AARWZ 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, founded in 1965 and headquartered in Wilmington, MA.

The ADM691A belongs to Analog Devices' microprocessor supervisory IC family, designed specifically for robust power monitoring, battery backup control, and firmware integrity assurance in mission-critical embedded systems.

FAQ

What is the reset threshold voltage of the ADM691AARWZ and how tightly is it specified?

The ADM691AARWZ has a nominal reset threshold of 4.65 V with a guaranteed tolerance of ±3%, corresponding to a min/max range of 4.50 V to 4.75 V across temperature and supply conditions. This specification ensures compatibility with +5 V systems operating within –5% to +10% tolerance, and is validated per the datasheet's "Reset Voltage Threshold" table under VCC = 4.75 V to 5.5 V and TA = –40°C to +85°C.

Can the ADM691AARWZ support both VCC-powered and battery-powered operation without external FETs?

Yes, the ADM691AARWZ natively supports seamless switchover between VCC and VBATT without external FETs: its internal PMOS switch delivers up to 250 mA from VCC (R_ON = 0.75 Ω typ), and its NMOS switch supplies up to 10 mA from VBATT (R_ON = 7 Ω typ). The BATT ON output can drive an external PNP if higher backup current is needed, but it is not required for basic CMOS RAM backup functionality in the ADM691AARWZ.

How does the watchdog timer behave immediately after power-on reset in the ADM691AARWZ?

In the ADM691AARWZ, the watchdog timer defaults to a 1.6 s timeout period immediately after power-on reset - regardless of whether the short (100 ms) mode is selected via OSC IN. This extended initial period allows the microprocessor sufficient time to initialize peripherals and establish stable software execution before watchdog supervision begins. Subsequent timeouts revert to the configured period (100 ms or 1.6 s) upon the first WDI transition after RESET deasserts.

What is the function of the dual RESET and RESET outputs on the ADM691AARWZ?

The ADM691AARWZ provides two complementary reset outputs: RESET is an active-low push-pull output, while RESET is an active-high open-drain output. This dual configuration allows direct interface with microprocessors requiring either polarity without external inverters. RESET sinks up to 50 µA at 0.3 V, and RESET requires an external pull-up to match the target logic level - enabling flexible system-level reset architecture in the ADM691AARWZ.

Does the ADM691AARWZ support external adjustment of reset and watchdog timeout periods, and if so, how?

Yes, the ADM691AARWZ supports external adjustment via OSC IN and OSC SEL pins. With OSC SEL grounded, connecting a capacitor (C) from OSC IN to GND yields reset timeout = 1200 × (C/47 pF) ms and watchdog timeout = 600 × (C/47 pF) ms. Alternatively, applying an external clock (f_CLK) to OSC IN gives reset timeout = 2048/f_CLK and watchdog timeout = 1024/f_CLK, enabling precise synchronization to system clocks in the ADM691AARWZ.