Analog Devices Inc./Maxim Integrated DS1818R-20/T&R

Overview

DS1818R-20/T&R from Maxim Integrated is a 3.3V fixed-threshold supervisory IC with pushbutton reset capability, active-low open-drain reset output, 150ms reset timeout, and ±20% VCC trip tolerance. It monitors power supply integrity and provides microprocessor reset during power-up, power-down, and manual pushbutton events in embedded control systems.

For engineers reviewing the DS1818R-20/T&R datasheet, DS1818R-20/T&R pinout, DS1818R-20/T&R application, or DS1818R-20/T&R equivalent, key selection criteria include reset threshold accuracy, pushbutton debounce timing, quiescent current, operating temperature range, and compatibility with 3.3V logic systems requiring reliable power-fail detection.

Technical Context

The DS1818R-20/T&R implements a precision temperature-compensated voltage reference and comparator to detect VCC deviations beyond its fixed ±20% trip window (2.47V–2.64V at 3.3V nominal). It asserts RST low on out-of-tolerance conditions and holds reset for 150ms after VCC recovery to ensure processor stabilization.

Its open-drain RST output includes an internal 5.5kΩ pullup resistor, enabling direct interface to microprocessor reset inputs without external components. Pushbutton reset is supported via RST line monitoring: pulling RST low for ≥1µs triggers a 150ms reset pulse upon release.

Key Specifications

Pinout & Package

DS1818R-20/T&R is supplied in SOT-23 package (3-pin, surface-mount), compatible with standard pick-and-place assembly. Pin assignments are identical across TO-92 and SOT-23 variants.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MAX6326–33D and TPS3808G33DBVR, the DS1818R-20/T&R uniquely combines ±20% trip tolerance, internal 5.5kΩ pullup, and pushbutton sensing in one SOT-23 package-reducing component count and simplifying design for cost-sensitive industrial applications where moderate threshold accuracy suffices.

Availability

DS1818R-20/T&R is available at Aetrix Electronics and suitable for industrial automation, smart metering, and network infrastructure applications requiring stable component supply, long-term lifecycle support, and RoHS-compliant packaging.

Supply support for DS1818R-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, automotive, communications, and computing markets.

The DS1818R-20/T&R belongs to the EconoReset™ family of supervisory ICs engineered for cost-effective, low-power microprocessor reset and power-monitoring in commercial and industrial embedded systems.

FAQ

What is the exact VCC trip voltage range for DS1818R-20/T&R?

The DS1818R-20/T&R has a guaranteed VCC trip point range of 2.47V (minimum) to 2.64V (maximum) at 3.3V nominal supply, corresponding to ±20% tolerance. This window is established by internal temperature-compensated reference circuitry and is validated across −40°C to +85°C operating temperature. The DS1818R-20/T&R does not support adjustable thresholds or external resistor programming.

Does DS1818R-20/T&R require an external pullup resistor on the RST pin?

No, the DS1818R-20/T&R integrates a 5.5kΩ internal pullup resistor on the RST pin, enabling direct connection to standard 3.3V microprocessor reset inputs without external components. This feature reduces BOM count and PCB area. An external pullup may still be used if stronger drive strength or different logic levels are needed, but it is not required for basic operation of the DS1818R-20/T&R.

How does DS1818R-20/T&R handle pushbutton reset events?

The DS1818R-20/T&R monitors the RST pin for low pulses: pulling RST low for ≥1µs triggers a reset cycle, and the output remains asserted low for 150ms after release. This built-in timing eliminates external RC debounce circuits. The DS1818R-20/T&R uses the same 150ms timeout for both power-up recovery and pushbutton events, ensuring consistent system behavior across reset sources.

What is the maximum supply voltage the DS1818R-20/T&R can tolerate?

The DS1818R-20/T&R supports a recommended VCC operating range of 1.0V to 5.5V, with absolute maximum rating of −0.5V to +7.0V on the VCC pin relative to GND. Operation above 5.5V is outside specification and may compromise reliability or parametric performance. The DS1818R-20/T&R's internal reference and comparator are optimized for 3.3V systems, though functional operation is verified down to 1.0V.

Is DS1818R-20/T&R pin-compatible with other DS1818 variants?

Yes, all DS1818 variants-including DS1818R-5, DS1818R-10, and DS1818R-20-are fully pin-compatible in both SOT-23 and TO-92 packages. They share identical pinout (RST/VCC/GND), electrical interface, timing behavior, and package dimensions. The only difference is the factory-trimmed VCC trip tolerance (±5%, ±10%, or ±20%), making them drop-in replacements for design flexibility without layout changes.