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Home > Products > Integrated Circuits (ICs) > Power Management (PMIC) > Supervisors

onsemi CAT1021YI-42-G

Name: CAT1021YI-42-G
Brand: onsemi
SKU: CAT1021YI-42-G
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: CAT1021YI-42-G

Manufacturer:: onsemi

Category:: Supervisors

Package:: 8-TSSOP (0.173", 4.40mm Width)

Datasheet:: CAT1021YI-42-G.pdf

Description:: CAT1021 - SUPERVISORY CIRCUIT WI

Quantity:: RFQ Add To RFQ list

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Product details

Overview

CAT1021YI-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 and supports industrial temperature range (−40°C to +85°C), used in microcontroller-based power-up sequencing and brownout protection for embedded control systems.

For engineers reviewing the CAT1021YI-42-G datasheet, pinout, applications, or equivalent options, key selection considerations include dual-reset polarity support, WP-enabled hardware write protection, 1.6 s watchdog timeout, 400 kHz I²C interface, and TSSOP-8 packaging with 3.0 mm × 4.4 mm footprint.

Technical Context

The CAT1021YI-42-G implements a precision bandgap-based V_CC sense circuit with 15 mV hysteresis and guaranteed reset validity down to V_CC = 1.0 V. Its dual open-drain RESET outputs (active-high and active-low) enable direct interfacing with diverse microcontrollers requiring either polarity.

Watchdog functionality monitors SDA transitions - not a dedicated WDI pin - and triggers reset if no activity occurs within 1.0–2.1 s. The integrated 2 kbit EEPROM uses 16-byte page writes, supports 1,000,000 program/erase cycles, and features hardware data protection tied to V_CC status and optional WP pin assertion.

Key Specifications

Parameter	Value and Actual Design Meaning
Reset Threshold	4.25 V to 4.50 V - ensures reliable reset assertion during brownout in 5 V systems
I²C Clock Frequency	400 kHz - enables fast configuration and parameter storage without bus contention
EEPROM Capacity	2 kbit (256 bytes) with 16-byte page write - reduces write latency vs. byte-by-byte programming
Power Supply Range	2.7 V to 5.5 V - supports both 3.3 V and 5 V microcontroller domains
Watchdog Timeout	1.0–2.1 s (typ. 1.6 s) - provides robust system recovery timing for firmware hang detection
Operating Temperature	−40°C to +85°C - qualified for industrial-grade embedded applications
Reset Timeout Delay	130–270 ms after V_CC > V_TH - guarantees stable MCU initialization before release

Pinout & Package

Package: 8-pin TSSOP (Case 948S), 3.0 mm × 4.4 mm footprint, 1.2 mm max height, RoHS-compliant NiPdAu finish.

Pin/Terminal	Circuit Role	Design Meaning
1 MR	Manual Reset Input	Debounced active-low input; initiates reset when pulled low, with internal pull-up
2 RESET	Active-Low Reset Output	Open-drain output requiring external pull-up; asserts during brownout or watchdog timeout
3 WP	Write Protect Input	Hardware lock: ties EEPROM array read-only when driven high (V_CC)
4 VSS	Ground	Reference return for all analog and digital circuitry
5 VCC	Power Supply	2.7–5.5 V supply powering supervisor logic and EEPROM core
6 RESET	Active-High Reset Output	Open-drain output requiring external pull-down; complements active-low RESET
7 SCL	I²C Clock Input	Master-generated clock synchronizing EEPROM read/write transactions
8 SDA	I²C Data I/O	Bidirectional open-drain line shared with watchdog monitoring path

Key Features

Feature	Design Value
Dual-polarity reset outputs	Simultaneous active-high and active-low signals eliminate level-shifting needs for mixed-logic systems
Hardware write protection (WP)	Prevents accidental EEPROM overwrites during power transients or firmware faults
V_CC-monitored EEPROM disable	Automatically blocks all memory access when V_CC drops below reset threshold
SDA-monitored watchdog timer	Uses existing I²C data line for supervision-no extra pin or routing required
Guaranteed reset at 1.0 V V_CC	Ensures deterministic reset behavior even during deep brownout conditions

Applications

Industrial PLC I/O Module	Smart Energy Meter
Use Scenario: Power sequencing and firmware integrity monitoring in DIN-rail mounted programmable logic controllers. IC Role / Device Role / Timing Role: Supervisory IC providing brownout reset, manual reset via front-panel button, and nonvolatile parameter storage. Use Value: Dual-reset polarity interfaces directly with both 3.3 V FPGA configuration logic and 5 V analog sensor interfaces without translation.	Use Scenario: Tamper-resistant calibration storage and supply monitoring in ANSI C12.20-certified electricity meters. IC Role / Device Role / Timing Role: System supervisor ensuring meter MCU resets cleanly during AC line dips and storing tariff tables in protected EEPROM. Use Value: WP pin prevents unauthorized calibration changes; 100-year data retention meets utility long-life requirements.
Medical Infusion Pump Controller	Automotive Body Control Module (BCM)
Use Scenario: Safety-critical power-on self-test and fault logging in battery-powered infusion devices. IC Role / Device Role / Timing Role: Resets pump MCU on undervoltage, logs error codes to EEPROM, and triggers watchdog if motor control loop hangs. Use Value: 1.6 s watchdog timeout aligns with FDA Class II response-time guidelines for therapeutic device recovery.	Use Scenario: Microcontroller supervision and configuration storage in 12 V automotive body electronics. IC Role / Device Role / Timing Role: Monitors battery voltage during cold-crank events and stores seat/mirror position settings. Use Value: Valid reset operation down to V_CC = 1.0 V ensures reliable reset even during severe cranking dips to ~6 V.

Industrial PLC I/O Module

Smart Energy Meter

Use Scenario: Power sequencing and firmware integrity monitoring in DIN-rail mounted programmable logic controllers.

IC Role / Device Role / Timing Role: Supervisory IC providing brownout reset, manual reset via front-panel button, and nonvolatile parameter storage.

Use Value: Dual-reset polarity interfaces directly with both 3.3 V FPGA configuration logic and 5 V analog sensor interfaces without translation.

Use Scenario: Tamper-resistant calibration storage and supply monitoring in ANSI C12.20-certified electricity meters.

IC Role / Device Role / Timing Role: System supervisor ensuring meter MCU resets cleanly during AC line dips and storing tariff tables in protected EEPROM.

Use Value: WP pin prevents unauthorized calibration changes; 100-year data retention meets utility long-life requirements.

Medical Infusion Pump Controller

Automotive Body Control Module (BCM)

Use Scenario: Safety-critical power-on self-test and fault logging in battery-powered infusion devices.

IC Role / Device Role / Timing Role: Resets pump MCU on undervoltage, logs error codes to EEPROM, and triggers watchdog if motor control loop hangs.

Use Value: 1.6 s watchdog timeout aligns with FDA Class II response-time guidelines for therapeutic device recovery.

Use Scenario: Microcontroller supervision and configuration storage in 12 V automotive body electronics.

IC Role / Device Role / Timing Role: Monitors battery voltage during cold-crank events and stores seat/mirror position settings.

Use Value: Valid reset operation down to V_CC = 1.0 V ensures reliable reset even during severe cranking dips to ~6 V.

Equivalent & Alternatives

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

Alternative Part	Technical Difference	Application Difference	Selection Advice
MAX6361KA29+T	Single active-low reset only; no active-high output; no WP pin; 1 kbit EEPROM	Lacks dual-reset flexibility and hardware write protection; lower EEPROM density	Select when board space is constrained and only one reset polarity is needed
TPS3808G125DBVR	No integrated EEPROM; standalone supervisor with adjustable reset threshold (1.25 V); 200 ms fixed timeout	Requires external memory for configuration storage; no I²C interface	Select when higher reset accuracy or adjustable delay is prioritized over embedded memory

Compared with MAX6361KA29+T and TPS3808G125DBVR, CAT1021YI-42-G uniquely combines dual-reset outputs, WP-enabled EEPROM protection, and SDA-monitored watchdog in a single TSSOP-8 package-reducing BOM count and PCB area while enabling secure, self-contained system supervision.

Availability

CAT1021YI-42-G is available at Aetrix Electronics and suitable for industrial automation, smart metering, medical instrumentation, and automotive body electronics requiring stable component supply across extended temperature ranges and long product lifecycles.

Supply support for CAT1021YI-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, sensors, and connectivity solutions for automotive, industrial, cloud, and IoT applications.

The CAT1021 family was designed to consolidate power supervision, reset generation, and nonvolatile configuration storage into a single IC for resource-constrained microcontroller systems-reducing design complexity and improving system reliability.

FAQ

What is the function of the WP pin on CAT1021YI-42-G?

The WP (Write Protect) pin on CAT1021YI-42-G disables all EEPROM write operations when driven high (tied to V_CC). When WP is low or floating, full read/write access is enabled. This hardware-level protection prevents accidental overwrites during power-up/down or firmware errors, and CAT1021YI-42-G includes an internal pull-down resistor on WP to ensure safe default behavior.

Does CAT1021YI-42-G support both 3.3 V and 5 V systems?

Yes, CAT1021YI-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. Its I²C interface is level-tolerant, and reset outputs remain valid down to V_CC = 1.0 V-ensuring robust supervision in mixed-voltage designs where CAT1021YI-42-G interfaces with both 3.3 V MCUs and 5 V peripherals.

How does the watchdog timer work on CAT1021YI-42-G?

The CAT1021YI-42-G watchdog timer monitors SDA line transitions and resets the system if no activity occurs within 1.0–2.1 s (typ. 1.6 s). Unlike CAT1023, it does not use a dedicated WDI pin. The timer clears on any SDA edge and remains inactive while RESET outputs are asserted. This design eliminates extra pins while providing fail-safe recovery for firmware hangs in CAT1021YI-42-G implementations.

What is the EEPROM endurance and data retention of CAT1021YI-42-G?

CAT1021YI-42-G guarantees 1,000,000 program/erase cycles and 100 years of data retention under industrial temperature conditions (−40°C to +85°C), per MIL-STD-883 testing. These specifications apply to its 2 kbit (256-byte) EEPROM array, which uses 16-byte page writes to minimize wear and maximize write throughput-making CAT1021YI-42-G suitable for frequent calibration or event-logging applications.

Can CAT1021YI-42-G be used in automotive applications?

CAT1021YI-42-G is rated for −40°C to +85°C (industrial grade) and is not AEC-Q100 qualified. While it has been deployed in non-safety-critical automotive body electronics (e.g., mirror/seat control modules), CAT1021YI-42-G is not recommended for engine bay or ADAS applications. For automotive-qualified alternatives, consult onsemi's AEC-Q100-certified supervisory portfolio-CAT1021YI-42-G serves best in industrial and commercial environments.

CAT1021YI-42-G Specifications

Product attributes: Attribute value

Manufacturer:: onsemi

Series:: CAT1021

Package/Case:: 8-TSSOP (0.173", 4.40mm Width)

Packaging:: Bulk

Product Status:: Obsolete

Programmable:: Not Verified

Type:: Simple Reset/Power-On Reset

Number of Voltages Monitored:: 1

Voltage - Threshold:: 4.25V, 4.5V

Output:: Open Drain or Open Collector

Reset:: Active High/Active Low

Reset Timeout:: 130ms Minimum

Operating Temperature:: -40°C ~ 85°C

Grade:: -

Qualification:: -

Mounting Type:: Surface Mount

Supplier Device Package:: 8-TSSOP

CAT1021YI-42-G FAQ

1.How can I place an order for CAT1021YI-42-G through Aetrix?

Please submit a Request for Quotation (RFQ) for CAT1021YI-42-G on Aetrix. Our sales agent will provide a competitive quotation and guide you through the order confirmation once you accept the terms.

2.Are the price and stock information for CAT1021YI-42-G reliable?

The price and inventory of CAT1021YI-42-G are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for CAT1021YI-42-G is usually 5 days.

3.What payment methods are accepted for CAT1021YI-42-G?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for CAT1021YI-42-G transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for CAT1021YI-42-G?

CAT1021YI-42-G orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your CAT1021YI-42-G order is processed, you will receive an email with the shipment details and tracking number.

Note: Tracking information may take up to 24 hours to appear. Express delivery typically takes 3–5 business days.

5.How can I obtain technical support or documentation for CAT1021YI-42-G?

For technical support, including CAT1021YI-42-G datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your CAT1021YI-42-G requirements.

6.How does Aetrix verify that CAT1021YI-42-G is sourced from the original manufacturer or authorized distributors?

All CAT1021YI-42-G products on Aetrix are procured from qualified distributors and authorized channels. Our dedicated quality assurance team conducts strict verification, including traceability checks and, if necessary, third-party testing. This ensures that CAT1021YI-42-G meets industry standards.

7.What is the process for return or replacement of CAT1021YI-42-G?

All CAT1021YI-42-G units undergo pre-shipment inspection (PSI). If there is an issue with CAT1021YI-42-G, returns or replacements are accepted under the following conditions:

1.Quantity discrepancies, incorrect items, or visible external defects (such as breakage or corrosion), acknowledged by Aetrix.

2.The issue is reported within 90 days of delivery.

3.The CAT1021YI-42-G part is unused and in its original packaging.

Return procedure for CAT1021YI-42-G:

1.Submit a request within 90 days.

2.Obtain a Return Material Authorization (RMA) from Aetrix.

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