Analog Devices Inc. ADM6321AX29ARJZ-R7

Overview

ADM6321AX29ARJZ-R7 from Analog Devices is a supervisory circuit with watchdog timer and open-drain active-low reset output in 5-lead SOT-23 package. It monitors VCC for undervoltage (2.93 V threshold), provides 1 ms minimum reset timeout, and features 102 ms typical watchdog timeout. Used in microprocessor systems to ensure reliable power-on, brownout, and code-execution recovery.

For engineers reviewing the ADM6321AX29ARJZ-R7 datasheet, ADM6321AX29ARJZ-R7 pinout, ADM6321AX29ARJZ-R7 application, or ADM6321AX29ARJZ-R7 equivalent, key selection criteria include reset threshold accuracy (±2.5% over −40°C to +85°C), guaranteed reset validity down to VCC = 1 V, open-drain output compatibility with mixed-voltage logic, and watchdog pulse width tolerance (50 ns min).

Technical Context

The ADM6321AX29ARJZ-R7 integrates a precision voltage reference, comparator-based reset generator, and edge-triggered watchdog timer cleared by WDI transitions. Its open-drain RESET output requires an external pull-up and supports level-shifting across logic families.

It features internal MR pull-up (52 kΩ), glitch rejection on MR (100 ns), and power supply immunity against fast transients - validated for 2.93 V threshold parts up to 100 mV overdrive for ≤8 µs duration per Figure 14.

Key Specifications

Pinout & Package

Package: 5-lead SOT-23 (RJ-5), JEDEC MO-178-AA compliant, RoHS-compliant (Z suffix).

Key Features

Applications

Equivalent & Alternatives

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

Compared with MAX6321XR29D3+T and TPS3808G33DBVR, the ADM6321AX29ARJZ-R7 uniquely combines 2.93 V precision threshold, 1 ms short-reset timing, open-drain flexibility, and dual active-low/active-high RESET outputs - critical for interoperability with legacy and modern MCUs in space-constrained industrial designs.

Availability

ADM6321AX29ARJZ-R7 is available at Aetrix Electronics and suitable for industrial PLC controllers, medical handheld diagnostics, and smart energy meters requiring stable component supply, long-term lifecycle support, and RoHS-compliant packaging.

Supply support for ADM6321AX29ARJZ-R7 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 ADM63xx family was designed specifically for robust microprocessor supervision in harsh environments - delivering precise voltage monitoring, configurable watchdog timing, and flexible reset signaling in ultra-small packages.

FAQ

What is the exact reset threshold voltage of the ADM6321AX29ARJZ-R7 and how does it vary with temperature?

The ADM6321AX29ARJZ-R7 has a nominal reset threshold of 2.93 V, with ±2.5% tolerance over the full industrial temperature range (−40°C to +85°C). At 25°C, the threshold is 2.93 V ±1.5%. Its temperature coefficient is 40 ppm/°C, meaning drift is bounded and predictable - critical for systems operating across wide ambient conditions without recalibration.

Does the ADM6321AX29ARJZ-R7 require an external pull-up resistor on the RESET pin, and why?

Yes, the ADM6321AX29ARJZ-R7 requires an external pull-up resistor on its open-drain RESET pin (Pin 1) because the output stage cannot actively drive high. A 10 kΩ resistor to the target logic rail (e.g., 3.3 V or 5 V) is typical. This design enables level-shifting and wired-OR configurations - a key advantage over push-pull alternatives when interfacing with multiple voltage domains.

How does the watchdog timer in the ADM6321AX29ARJZ-R7 respond to WDI signal transitions?

The ADM6321AX29ARJZ-R7 watchdog timer clears on any logic transition - low-to-high or high-to-low - at the WDI pin (Pin 4), with minimum pulse width of 50 ns. If no transition occurs within 102 ms (typical), RESET asserts. Leaving WDI floating disables the watchdog, and the timer also resets automatically during VCC undervoltage or MR-initiated reset events.

Can the ADM6321AX29ARJZ-R7 operate reliably when VCC drops below 2.0 V?

Yes, the ADM6321AX29ARJZ-R7 guarantees valid reset output behavior down to VCC = 1 V. Both RESET outputs remain functional in this range: the open-drain RESET can still sink current, and the active-high RESET maintains defined logic levels. This ensures fail-safe operation during deep brownout - a requirement for safety-critical and battery-depleted scenarios.

What is the purpose of the second RESET pin (Pin 3) on the ADM6321AX29ARJZ-R7?

Pin 3 on the ADM6321AX29ARJZ-R7 is an active-high push-pull RESET output, complementing the open-drain active-low RESET on Pin 1. This dual-output architecture allows simultaneous reset signaling to two different subsystems - for example, driving an active-high enable on an analog front-end while asserting active-low reset on a microcontroller - all from a single supervisory IC.