Analog Devices Inc. ADM823SYRJ-R7

Overview

ADM823SYRJ-R7 from Analog Devices is a supervisory circuit with integrated watchdog timer and manual reset input, designed for microprocessor supply voltage monitoring and code execution integrity assurance. It features a 2.93 V reset threshold (±50 mV over temperature), 140 ms minimum reset timeout, 1.6 sec typical watchdog timeout, push-pull active-low RESET output, and operates across −40°C to +125°C. It is used in automotive-grade embedded controllers requiring reliable brownout and software-failure recovery.

For engineers reviewing the ADM823SYRJ-R7 datasheet, ADM823SYRJ-R7 pinout, ADM823SYRJ-R7 application, or ADM823SYRJ-R7 equivalent, key selection criteria include reset threshold accuracy, guaranteed reset validity down to VCC = 1 V, watchdog pulse width tolerance (50 ns), MR input glitch rejection (100 ns), and SOT-23-5 package compatibility with space-constrained PCB layouts.

Technical Context

The ADM823SYRJ-R7 implements a precision bandgap-based voltage reference with 40 ppm/°C temperature coefficient and 5 mV hysteresis to ensure stable reset assertion during VCC transients. Its internal watchdog timer resets on missing logic transitions at WDI - cleared by any low-to-high or high-to-low edge - and is disabled when WDI floats.

Reset generation combines three independent triggers: undervoltage on VCC below 2.93 V, manual assertion via MR (active-low, 1 µs minimum pulse), or watchdog timeout. The push-pull RESET output guarantees logic-low state down to VCC = 1 V with 3.2 mA sink capability at VTH min, supporting direct interface to 3.3 V and 5 V microcontrollers without external pull-ups.

Key Specifications

Pinout & Package

ADM823SYRJ-R7 is housed in a 5-lead SOT-23 (RJ-5) package per JEDEC MO-178-AA, with 0.95 mm pitch, 2.90 mm × 1.60 mm body, and 1.10 mm max height - optimized for automated placement and thermal performance (θJA = 270°C/W).

Key Features

Applications

Equivalent & Alternatives

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

Compared with MAX6326UT29D3+T and TPS3808G33DBVR, the ADM823SYRJ-R7 uniquely integrates watchdog timer, manual reset, and push-pull output in a single SOT-23-5 package - enabling full system supervision without external logic or passives, while maintaining automotive-grade temperature range and transient immunity.

Availability

ADM823SYRJ-R7 is available at Aetrix Electronics and suitable for automotive engine control units, industrial PLC modules, medical infusion pump controllers, and smart energy meter subsystems requiring stable component supply with long-term lifecycle support.

Supply support for ADM823SYRJ-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 semiconductor company specializing in high-performance analog, mixed-signal, and digital signal processing technologies for precision measurement and control.

The ADM823 family is part of Analog Devices' supervisory IC portfolio, engineered for automotive and industrial applications demanding guaranteed reset behavior, watchdog reliability, and operation across extended temperature ranges.

FAQ

What is the exact reset threshold voltage of ADM823SYRJ-R7 and how does it vary with temperature?

The ADM823SYRJ-R7 has a nominal reset threshold of 2.93 V at 25°C, with a specified range of 2.85 V to 3.00 V over the full −40°C to +125°C operating temperature range. Its temperature coefficient is tightly controlled at 40 ppm/°C, ensuring minimal drift across environmental conditions. This makes ADM823SYRJ-R7 suitable for 3.3 V systems where precise brownout detection is critical, and the 5 mV hysteresis prevents oscillation during slow VCC recovery.

Does ADM823SYRJ-R7 support watchdog functionality, and what are the timing requirements for the WDI pin?

Yes, ADM823SYRJ-R7 includes a watchdog timer with a typical timeout of 1.6 seconds (1.12–2.40 sec range). The WDI pin must receive a logic transition - either low-to-high or high-to-low - at least once within each timeout period to prevent reset assertion. Pulses as narrow as 50 ns are recognized, allowing efficient GPIO toggling in firmware. Leaving WDI unconnected disables the watchdog function entirely, as internal circuitry isolates the timer from the reset path.

Can ADM823SYRJ-R7 generate a valid reset signal when VCC drops below 1.5 V?

Yes, ADM823SYRJ-R7 guarantees valid RESET output down to VCC = 1 V - meaning it continues to assert a clean logic-low signal even as the supply collapses. At VCC = 1 V, the RESET output sinks 50 µA while maintaining ≤0.3 V, ensuring compatibility with microcontrollers that retain input recognition at low VCC. This behavior is confirmed across temperature and distinguishes ADM823SYRJ-R7 from many competitors whose reset outputs become indeterminate below 1.8 V.

What is the internal pull-up resistance on the MR pin of ADM823SYRJ-R7, and how does it affect external button design?

The MR pin of ADM823SYRJ-R7 features a factory-trimmed 52 kΩ internal pull-up resistor to VCC, eliminating the need for an external component. This allows direct connection of a momentary push-button between MR and GND. With this configuration, a 1 µs minimum low pulse is sufficient to trigger reset, and the integrated 100 ns glitch rejection filters out contact bounce and EMI. No external capacitor or resistor is required unless additional noise immunity is needed in harsh environments.

Is ADM823SYRJ-R7 pin-compatible with other members of the ADM823/824/825 family, and what are the key functional differences?

No, ADM823SYRJ-R7 is not pin-compatible with ADM824 or ADM825 variants due to differing pin functions: ADM824 uses Pin 3 as RESET (active-high), while ADM825 uses Pin 3 as MR - whereas ADM823SYRJ-R7 uses Pin 3 as MR (active-low). All share identical SOT-23-5 pinout geometry and footprint, but swapping them requires PCB layout changes. Functionally, only ADM823 supports both WDI and MR; ADM824 omits MR, and ADM825 omits WDI - making ADM823SYRJ-R7 the sole choice when both watchdog and manual reset are required.