Diodes Incorporated ZSM300CSTOB

Overview

ZSM300CSTOB from Diodes Incorporated is an obsolete three-terminal under-voltage monitor IC with 3.00 V threshold, ±1.5% accuracy, 240 ms reset timeout, open-drain output, and operating supply range of 1.0 V to 6.0 V. It functions as a system supervisory device for microcontroller reset assertion during brownout conditions in embedded power management circuits.

For engineers reviewing the ZSM300CSTOB datasheet, ZSM300CSTOB pinout, ZSM300CSTOB application, or ZSM300CSTOB equivalent, key selection considerations include reset threshold tolerance, timeout duration, output drive type, supply voltage compatibility, and obsolescence status requiring migration planning.

Technical Context

The ZSM300CSTOB implements a precision bandgap reference and comparator-based monitoring architecture that triggers a reset signal when V_CC falls below 3.00 V ±1.5%. Its internal timer ensures a minimum 240 ms reset pulse width after supply recovery.

No external components are required: the device integrates threshold detection, timing, and open-drain output driver in a single SOT-23 package. It operates across industrial temperature range (–40°C to +85°C) with quiescent current of 1.1 µA typical.

Key Specifications

Pinout & Package

Package: SOT-23 (3-pin, standard outline per JEDEC TO-236AB).

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar under-voltage monitor applications.

Compared with ZSM300CSTOB, APX803L offers higher threshold accuracy while maintaining identical pinout and timing; APX803S provides push-pull output for simplified routing but sacrifices bus-sharing capability-both require no PCB redesign.

Availability

ZSM300CSTOB is available at Aetrix Electronics and suitable for microcontroller reset, industrial sensor node supervision, POS terminal power sequencing, and smart meter voltage monitoring requiring stable component supply despite its obsolete status.

Supply support for ZSM300CSTOB 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

Diodes Incorporated is a global manufacturer of discrete semiconductors and analog ICs, specializing in high-performance, high-reliability components for power management, signal integrity, and protection.

The ZSM300 belongs to Diodes' legacy voltage supervisor product line, designed specifically for cost-optimized, low-pin-count reset solutions in space-constrained embedded systems.

FAQ

Is ZSM300CSTOB still in production?

No. Diodes Incorporated has discontinued the ZSM300CSTOB and marked it as obsolete. The official datasheet (DS43794 Rev. 1–4, July 2021) states "PART OBSOLETE – USE APX803L/APX803S". Aetrix Electronics maintains limited legacy stock for design continuity and end-of-life support.

What is the function of the RESET pin on ZSM300CSTOB?

The RESET pin is an open-drain output that pulls low when V_CC drops below 3.00 V ±1.5%. It remains low for ≥240 ms after V_CC rises above threshold. An external pull-up resistor is mandatory to establish logic-high level and define voltage domain compatibility.

Can ZSM300CSTOB operate from a 1.8 V supply?

Yes. The ZSM300CSTOB supports supply voltages from 1.0 V to 6.0 V. At 1.8 V, it reliably monitors for undervoltage relative to its 3.00 V threshold-however, the output will not assert until V_CC reaches at least 3.00 V, so it cannot supervise rails below its threshold voltage.

Why does ZSM300CSTOB require no external capacitor?

The 240 ms reset timeout is implemented using an internal RC oscillator and counter, eliminating the need for external timing capacitors. This reduces BOM count, improves reliability, and ensures consistent timeout across temperature and voltage variations without component tolerances affecting timing.