Analog Devices Inc./Maxim Integrated DS1819BR-20-U

Overview

DS1819BR-20-U from Maxim Integrated is a 3.3V microprocessor supervisory circuit in SOT-23-5 package, providing precision power monitoring (±20% trip at 2.55–2.70V), watchdog timer (1.12s timeout), and active-low reset output. It halts and restarts out-of-control microprocessors during power transients or software lockup, and supports pushbutton override via debounced PBRST input. Used in embedded controllers requiring reliable power-up sequencing and fault recovery.

For engineers reviewing the DS1819BR-20-U datasheet, DS1819BR-20-U pinout, DS1819BR-20-U application, or DS1819BR-20-U equivalent, key selection criteria include VCC trip accuracy (20% for 3.0V systems), 140ms minimum reset pulse width, watchdog strobe timing compatibility, and SOT-23-5 footprint constraints in space-constrained industrial control modules.

Technical Context

The DS1819BR-20-U implements a precision voltage monitor with 5mV hysteresis and temperature-compensated reference to detect VCC drops below 2.55V (min) and hold RST active until VCC recovers and stabilizes for ≥140ms. Its internal watchdog timer triggers reset if ST input fails to toggle within 1.12s, and the PBRST pin accepts debounced external pushbutton signals to force reset on release.

This 'B' variant provides one active-low RST output (Pin 1) and one active-high RST output (Pin 3), both asserted for ≥140ms after power-up, power-down, or watchdog timeout. The ST input requires <10kHz square-wave drive with ≥200µA sink/source capability, and PBRST is internally pulled up to VCC (50kΩ typical).

Key Specifications

Pinout & Package

SOT-23-5 surface-mount package (2.9mm × 1.6mm × 1.1mm), lead-free and RoHS-compliant, optimized for high-density PCB layouts in compact industrial and automotive control units.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MAX823SEUR+T and TPS3808G12DBVR, the DS1819BR-20-U uniquely integrates 3.3V-specific ±20% monitoring, dual-reset outputs, watchdog timer, and debounced pushbutton support in a single SOT-23-5 device-reducing BOM count and PCB area while meeting industrial reset timing requirements without external components.

Availability

DS1819BR-20-U is available at Aetrix Electronics and suitable for industrial PLC controllers, smart energy meters, automotive body control modules, and medical infusion pump controllers requiring stable component supply across extended product lifecycles.

Supply support for DS1819BR-20-U 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, automotive, and communications applications.

The DS1819BR-20-U belongs to the MicroMonitor™ family of supervisory circuits, engineered specifically to replace discrete reset generators and watchdog timers in 3.3V microprocessor systems with guaranteed timing, low power, and high noise immunity.

FAQ

What is the exact VCC trip voltage range for DS1819BR-20-U?

The DS1819BR-20-U has a guaranteed VCC trip point of 2.55V (min) to 2.70V (max), corresponding to ±20% tolerance around 3.0V nominal supply. This range is specified over −40°C to +85°C and includes 5mV hysteresis to prevent oscillation near the threshold. The trip point is factory-trimmed and does not require external calibration.

Does DS1819BR-20-U support both active-low and active-high reset outputs simultaneously?

Yes, DS1819BR-20-U is the 'B' variant and provides two independent reset outputs: Pin 1 (RST) is active-low, and Pin 3 (RST) is active-high. Both outputs assert synchronously during power failure, watchdog timeout, or PBRST activation and remain active for ≥140ms, enabling direct interface to microcontrollers requiring either logic polarity.

Can the watchdog timer in DS1819BR-20-U be disabled, and how?

Yes, the watchdog timer in DS1819BR-20-U can be disabled by leaving the ST pin (Pin 4) floating or tri-stated. No external pull-up or pull-down is required-the internal circuitry interprets an open ST input as a permanent disable signal. This allows flexible configuration without modifying PCB layout or adding components.

What is the maximum allowed VCC slew rate during power-up for reliable DS1819BR-20-U operation?

The DS1819BR-20-U specifies a minimum VCC slew rate of 12.5V/s on the rising edge to ensure clean power-on reset assertion. Slower ramps may cause incomplete internal initialization or metastability in the voltage detector, potentially leading to missed reset pulses. For systems with slow-ramping supplies, a simple RC delay on VCC or use of a dedicated power-good signal is recommended.

Is DS1819BR-20-U compatible with 1.8V microcontrollers?

No, DS1819BR-20-U is not rated for direct interface with 1.8V logic. Its RST and RST outputs are push-pull and swing from GND to VCC (3.0V nominal), and its input thresholds (VIH = 0.8×VCC, VIL = 0.3×VCC) assume VCC ≥ 2.4V. Interfacing with 1.8V µPs requires level-shifting circuitry or selection of a dedicated 1.8V supervisory IC.