Analog Devices Inc./Maxim Integrated DS1231-20/G

Overview

DS1231-20/G from Maxim Integrated is a precision power monitor IC designed to detect impending power failure and initiate orderly processor shutdown before VCC drops below 4.75 V (5% threshold), provide non-maskable interrupt (NMI) on high-voltage input decay, and deliver dual active-high/active-low reset outputs with 150 ms power-up delay. It operates from +5 V supply, supports linear or switching power supplies, and requires no external capacitors.

For engineers reviewing the DS1231-20/G datasheet, DS1231-20/G pinout, DS1231-20/G application, or DS1231-20/G equivalent, key selection criteria include its dual-reset architecture (RST and RST), selectable 5%/10% VCC trip thresholds via TOL pin, high-impedance or current-source IN pin configurable by MODE, NMI timing response under voltage transients, and compatibility with microprocessor-based systems requiring fail-safe power sequencing.

Technical Context

The DS1231-20/G integrates two independent comparators: one monitors VCC against a temperature-compensated reference to generate RST/RST signals at 4.75 V (TOL = GND) or 4.5 V (TOL = VCC); the other monitors the IN pin with hysteresis-configured as high-impedance (VTP− = 2.3 V, MODE = VCC) or 30 µA current source (VTP+ = 2.5 V, MODE = GND). Both comparators feed digital samplers and delay logic to ensure noise-immune, deterministic timing.

Its internal bias network enables direct interface to AC line sensing via resistor dividers or opto-isolators without external components. The RST output is push-pull (active-high), while RST is open-drain (active-low), allowing flexible reset assertion across diverse processor families. Power-up reset duration is guaranteed ≥150 ms, and VCC detect-to-RST propagation is ≤100 ns.

Key Specifications

Pinout & Package

DS1231-20/G is supplied in an 8-pin DIP package (300 mil width), with lead finish Pb-free per JEDEC J-STD-020, RoHS-compliant.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar power monitor applications.

Compared with MAX690EPA+ and TPS3823-50DBVR, the DS1231-20/G uniquely delivers integrated NMI generation, dual-reset signaling, and configurable input sensing-enabling single-chip power-failure response without external comparators or timing components.

Availability

DS1231-20/G is available at Aetrix Electronics and suitable for industrial control systems, medical diagnostics equipment, telecom infrastructure, and point-of-sale terminals requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for DS1231-20/G 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) is a semiconductor company specializing in analog, mixed-signal, and power management ICs for industrial, automotive, and communications markets.

The DS1231-20/G belongs to Maxim's legacy power-monitoring product line, engineered specifically for fail-safe microprocessor systems where deterministic power-failure response, AC-line sensing, and nonvolatile memory protection are critical design requirements.

FAQ

What is the exact VCC trip voltage for DS1231-20/G when TOL is grounded?

The DS1231-20/G has a nominal VCC trip voltage of 4.75 V when the TOL pin is connected to GND, corresponding to a 5% drop from 5.0 V. Per datasheet page 7, the specified range is 4.50 V to 4.74 V at 0°C to 70°C, with typical value 4.62 V. This threshold ensures reset activation well before most microprocessors enter undefined operation.

How does the MODE pin affect the IN pin behavior in DS1231-20/G?

In DS1231-20/G, the MODE pin configures the IN pin (Pin 1): when MODE = VCC, IN becomes a high-impedance input with VTP− = 2.3 V; when MODE = GND, IN sources 30 µA with VTP+ = 2.5 V. This allows either resistor-divider AC sensing or opto-isolator interfacing-both validated in Figures 4–7 of the DS1231/S datasheet.

Does DS1231-20/G require external pull-up resistors, and if so, on which pins?

Yes, DS1231-20/G requires an external pull-up resistor on the RST pin (Pin 6), which is an open-drain output. The RST pin (Pin 5) is push-pull and does not require external pull-up. Datasheet page 8 explicitly states "RST requires a pull–up resistor" and confirms RST is active-low open-drain, while RST is active-high with internal drive capability.

What is the guaranteed minimum power-up reset duration for DS1231-20/G?

The DS1231-20/G guarantees a minimum power-up reset duration of 150 ms, as confirmed in the AC Electrical Characteristics table (page 8) and Timing Diagram: POWER-UP (page 9). This ensures the microprocessor remains held until the +5 V supply fully stabilizes, preventing boot failures due to premature release.

Can DS1231-20/G operate over the industrial temperature range?

Yes, DS1231-20/G is rated for the industrial temperature range of –40°C to +85°C, as stated in the Absolute Maximum Ratings section (page 7) under "Operating Temperature (Industrial Version)". This makes it suitable for deployment in harsh environments such as factory automation and outdoor telecom equipment.