Analog Devices Inc./Maxim Integrated DS1819AX-20+T&R

Overview

DS1819AX-20+T&R from Maxim Integrated is a 3.3V microprocessor supervisory circuit in SOT-23-5 package, providing precision power monitoring (20% trip threshold at 2.55–2.70 V), watchdog timer (1.12 s timeout), and pushbutton reset with 140 ms minimum active-reset pulse. It halts and restarts out-of-control microprocessors during power transients or software lockup in embedded industrial control systems.

For engineers reviewing the DS1819AX-20+T&R datasheet, DS1819AX-20+T&R pinout, DS1819AX-20+T&R application, or DS1819AX-20+T&R equivalent, key selection criteria include VCC trip accuracy (±20% for 3.0 V systems), watchdog strobe timing (1.12 s max), pushbutton debounce capability, active-low reset output drive strength (6 mA sink), and SOT-23-5 footprint compatibility with MAX823/24/25 family.

Technical Context

The DS1819AX-20+T&R implements a precision voltage monitor with 5 mV hysteresis, a 1.12 s watchdog timer triggered by ST input transitions, and a debounced PBRST input that generates a guaranteed 140–280 ms active-low reset pulse upon button release. Its RST output uses a push-pull driver valid down to 1.0 V VCC and supports 0 V operation with external pull-down.

It operates across -40°C to +85°C, draws only 8–12 µA quiescent current at 3.6 V, and features noise immunity against <100 ns pulses on PBRST and <2 µs glitches at VCCTP. The device is functionally identical to DS1819A but marked with 'X' denoting tape-and-reel packaging and '20' specifying ±20% tolerance.

Key Specifications

Pinout & Package

SOT-23-5 surface-mount package (2.9 mm × 1.6 mm × 1.1 mm), lead-free and RoHS-compliant, optimized for space-constrained PCB layouts in portable and industrial electronics.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MAX823SEUK+T and TPS3808G12DBVR, the DS1819AX-20+T&R delivers fixed ±20% 3.0 V supervision with minimal external components, lower operating current, and integrated pushbutton debounce-making it optimal for cost-sensitive, space-constrained 3.3 V embedded systems requiring guaranteed 140 ms reset timing.

Availability

DS1819AX-20+T&R is available at Aetrix Electronics and suitable for industrial automation, medical instrumentation, smart metering, and automotive body electronics requiring stable component supply and long-term lifecycle support.

Supply support for DS1819AX-20+T&R 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

Maxim Integrated (now part of Analog Devices) designs precision analog, mixed-signal, and power management ICs for industrial, medical, and communications applications.

The DS1819AX-20+T&R belongs to the MicroMonitor™ family of supervisory circuits engineered specifically for reliable microprocessor reset generation, power-fail detection, and watchdog protection in 3.3 V embedded systems.

FAQ

What is the exact VCC trip voltage range for DS1819AX-20+T&R?

The DS1819AX-20+T&R has a guaranteed VCC trip point of 2.55 V to 2.70 V, corresponding to ±20% tolerance around a nominal 3.0 V supply. This range is specified under -40°C to +85°C and ensures consistent reset assertion before brownout conditions affect microprocessor operation. The device uses a temperature-compensated internal reference to maintain accuracy across its full operating temperature range.

Does DS1819AX-20+T&R support both watchdog and pushbutton reset functions simultaneously?

Yes, DS1819AX-20+T&R supports both functions concurrently. As a Type 'A' variant, it includes both the ST (strobe) input for watchdog monitoring and the PBRST (pushbutton reset) input for manual override. The watchdog timer resets the RST output if ST is not toggled within 1.12 seconds, while pressing the pushbutton asserts RST for ≥140 ms upon release-both actions independently trigger the same active-low reset signal.

Can DS1819AX-20+T&R operate down to 0 V VCC?

Yes, DS1819AX-20+T&R maintains valid RST output down to 0 V VCC when an external 100 kΩ pull-down resistor is connected from RST to ground. Without the resistor, the push-pull output remains functional down to 1.0 V VCC. This dual-mode capability ensures fail-safe reset assertion during full power collapse, critical for data integrity in battery-backed or energy-harvesting systems.

Is DS1819AX-20+T&R pin-compatible with MAX823 series devices?

Yes, DS1819AX-20+T&R is pin- and function-compatible with the MAX823/24/25 family in SOT-23-5 package. Pin 1 (RST), Pin 2 (GND), Pin 3 (PBRST), Pin 4 (ST), and Pin 5 (VCC) match identically. However, DS1819AX-20+T&R is optimized for 3.0 V systems (2.55–2.70 V trip), whereas MAX823 variants target 5 V rails-so voltage-level compatibility must be verified per application.

What is the maximum recommended slew rate for VCC during power-up of DS1819AX-20+T&R?

The DS1819AX-20+T&R specifies a minimum VCC slew rate of 12.5 V/s during rising edge to ensure reliable power-on reset timing. Slower ramp rates may cause premature RST deassertion before the microprocessor's internal regulators stabilize. For systems with slow-ramping supplies, adding a small RC delay on the VCC rail or selecting a supervisory IC with adjustable delay may be necessary to meet this requirement.