onsemi CAT1021ZI-42-G

Overview

CAT1021ZI-42-G from onsemi is a supervisory circuit integrating 2 kbit I²C EEPROM, precision V_CC monitor (4.25–4.50 V threshold), active-high and active-low reset outputs, manual reset input (MR), and watchdog timer monitoring SDA. It operates from 2.7 V to 5.5 V, supports industrial temperature range (−40°C to +85°C), and uses MSOP-8 package for space-constrained microcontroller power-up supervision in embedded control systems.

For engineers reviewing the CAT1021ZI-42-G datasheet, pinout, applications, or equivalent options, key selection criteria include reset threshold accuracy, dual-reset polarity support, WP pin availability, I²C write protection behavior, and compatibility with brownout-prone 3.3 V/5 V systems requiring guaranteed reset assertion down to V_CC = 1.0 V.

Technical Context

The CAT1021ZI-42-G implements a precision bandgap-based V_CC sense circuit with 15 mV hysteresis and guarantees valid reset output down to 1.0 V supply. Its watchdog timer monitors SDA transitions and triggers reset after 1.0–2.1 s of inactivity - identical to CAT1022 but distinct from CAT1023's dedicated WDI pin.

It features hardware write protection via the WP pin (tied to V_CC disables all EEPROM writes), 16-byte page write buffer, and automatic EEPROM disable during reset assertion. The device uses open-drain RESET/RESET outputs requiring external pull-up/pull-down resistors and includes debounced MR input with 100 ns glitch immunity.

Key Specifications

Pinout & Package

Package: 8-pin MSOP (Z suffix), 3.0 mm × 3.0 mm footprint, 0.8 mm max height, RoHS-compliant NiPdAu finish.

Key Features

Applications

Equivalent & Alternatives

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

Compared with CAT1021ZI-42-G, CAT1021ZI-45-G shifts brownout detection upward for stricter 5 V regulation compliance, while CAT1022ZI-42-G removes WP and one reset output to reduce cost and complexity where dual-reset polarity and hardware write lock are not required.

Availability

CAT1021ZI-42-G is available at Aetrix Electronics and suitable for industrial PLC I/O modules, smart energy meters, medical handheld diagnostics, and automotive body control units requiring stable component supply with guaranteed long-term obsolescence management.

Supply support for CAT1021ZI-42-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

onsemi (formerly ON Semiconductor) is a global semiconductor supplier specializing in energy-efficient power management, analog, sensor, and connectivity solutions for automotive, industrial, cloud, and consumer markets.

The CAT1021 family is designed as an integrated supervisory + memory solution for microcontroller-based systems needing reliable power-up sequencing, brownout protection, and nonvolatile configuration storage in minimal footprint.

FAQ

What is the function of the WP pin on the CAT1021ZI-42-G?

The WP (Write Protect) pin on the CAT1021ZI-42-G disables all EEPROM write operations when driven high (tied to V_CC). When left unconnected or grounded, writes are enabled. This hardware-level protection prevents accidental overwrites during power transients or firmware errors. The CAT1021ZI-42-G includes this pin, distinguishing it from CAT1022 variants. Internal pull-down ensures safe default operation unless explicitly asserted.

Does the CAT1021ZI-42-G support both 3.3 V and 5 V systems?

Yes, the CAT1021ZI-42-G operates across 2.7 V to 5.5 V and features a 4.25–4.50 V reset threshold optimized for 5 V systems, while its wide V_CC range and 1.0 V reset validity enable robust use in 3.3 V domains with appropriate decoupling. Its I²C interface complies with standard-mode timing at both voltages, and the MSOP-8 package supports mixed-voltage board layouts without level-shifting.

How does the watchdog timer work on the CAT1021ZI-42-G?

On the CAT1021ZI-42-G, the watchdog timer monitors SDA line activity and resets the system if no transition occurs within 1.0–2.1 seconds. It is cleared by any SDA edge and remains inactive while RESET outputs are asserted. Unlike CAT1023, it lacks a dedicated WDI pin - this architecture reduces pin count while maintaining fail-safe recovery from software hangs in I²C-connected microcontrollers.

What is the EEPROM endurance and data retention of the CAT1021ZI-42-G?

The CAT1021ZI-42-G provides 1,000,000 program/erase cycles and 100 years of data retention at +25°C per MIL-STD-883 testing. These specifications apply to its 2 kbit (256-byte) serial EEPROM with 16-byte page write capability. Real-world endurance may vary with temperature and voltage stress, but the rated values ensure suitability for infrequent configuration updates in industrial and medical applications over decades.

Can the CAT1021ZI-42-G be used in automotive applications?

The CAT1021ZI-42-G is qualified for industrial temperature range (−40°C to +85°C) and meets AEC-Q100 stress test requirements for some variants, but the ZI-42-G specifically is not automotive-qualified. For under-hood automotive body control modules, it may be deployed in controlled environments with additional thermal margin analysis. Designers requiring full AEC-Q100 Grade 2 (−40°C to +105°C) compliance should verify qualification status directly with onsemi or select an automotive-grade variant.