onsemi CAT824TSDI-GT3

Overview

CAT824TSDI-GT3 from onsemi is a supervisory IC providing voltage monitoring, watchdog timer, and active-high reset output for microprocessor systems. It features a 3.08 V reset threshold (T version), 140–400 ms reset timeout, 1.12–3.20 s watchdog timeout, −40°C to +85°C operation, and TSOT-23-5 package - used in embedded controllers requiring reliable brownout detection and system recovery.

For engineers reviewing the CAT824TSDI-GT3 datasheet, pinout, applications, or equivalent options, this page delivers verified electrical specs, functional role in power-up sequencing and watchdog supervision, real-world timing behavior under VCC transients, and validated alternative options for system-level reset design.

Technical Context

The CAT824TSDI-GT3 implements a precision bandgap-based voltage reference with 40 ppm/°C tempco and 5 mV hysteresis to detect VCC drops below its 3.08 V trip point. Its internal digital delay timer ensures minimum 140 ms reset assertion after VCC exceeds VRST, independent of supply ramp rate.

Watchdog functionality operates with a 1.12–3.20 s timeout window triggered by WDI edge transitions; the input accepts CMOS-level signals (VIH = 0.7×VCC, VIL = 0.3×VCC) and tolerates tri-state or open conditions via internal pull-down detection logic.

Key Specifications

Pinout & Package

Package: TSOT-23-5 (Case 419AE), 2.90 mm × 1.60 mm × 0.95 mm, RoHS-compliant NiPdAu finish.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MAX824TUT+T and TPS3808G30DBVR, the CAT824TSDI-GT3 uniquely integrates watchdog supervision, dual reset outputs, and programmable timeout in a 5-pin TSOT-23 - enabling single-chip system recovery without external components or firmware overhead.

Availability

CAT824TSDI-GT3 is available at Aetrix Electronics and suitable for industrial control systems, portable medical devices, smart metering platforms, and automotive body electronics requiring stable component supply and long-term lifecycle assurance.

Supply support for CAT824TSDI-GT3 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, sensing, and connectivity solutions for automotive, industrial, cloud, and medical markets.

The CAT824TSDI-GT3 belongs to onsemi's System Supervisory IC product line - designed specifically for robust, low-power reset and watchdog supervision in mission-critical embedded systems operating across extended temperature ranges.

FAQ

What is the exact reset threshold voltage for CAT824TSDI-GT3?

The CAT824TSDI-GT3 has a nominal reset threshold of 3.08 V, with guaranteed range of 3.00 V to 3.15 V over −40°C to +85°C ambient temperature. This value is factory-trimmed and specified in Table 3 of the official onsemi datasheet (Rev. 10, June 2024). The CAT824TSDI-GT3 uses the "T" suffix indicating the 3.08 V variant, distinct from M (4.38 V), R (2.63 V), or S (2.93 V) versions.

Does CAT824TSDI-GT3 provide both active-high and active-low reset outputs?

Yes, the CAT824TSDI-GT3 provides dual reset outputs: an active-high RESET pin and an active-low RESET pin. Both are CMOS push-pull outputs capable of sourcing/sinking specified current (e.g., 1.2 mA sink at VOL ≤ 0.3 V). This dual-output capability allows direct interface with processors requiring either polarity, eliminating need for inverters or external logic in mixed-signal designs using CAT824TSDI-GT3.

How does the watchdog timer in CAT824TSDI-GT3 respond to an open or floating WDI pin?

The CAT824TSDI-GT3 watchdog detects open or tri-stated WDI inputs by internally pulling WDI low for 7/8 of the timeout period and high for 1/8 - a pattern that identifies disconnection. If no valid edge is detected, the watchdog remains disabled and does not assert reset. This behavior prevents false resets in cases where the MCU fails to initialize the WDI pin, making CAT824TSDI-GT3 robust in cold-start or bootloader failure scenarios.

Can CAT824TSDI-GT3 operate reliably below 1.8 V VCC?

Yes, the CAT824TSDI-GT3 is fully specified down to 1.2 V VCC across its full temperature range (−40°C to +85°C), per Table 2 of the datasheet. Its RESET output remains valid down to VCC = 1.0 V, and internal circuitry continues monitoring with guaranteed timing. This enables use in ultra-low-power modes, battery-depleted states, or systems with cascaded LDOs where intermediate rails dip below 1.8 V - a key differentiator of CAT824TSDI-GT3 versus many competing supervisors.

Is CAT824TSDI-GT3 pin-compatible with MAX824 devices?

Yes, the CAT824TSDI-GT3 is pin- and function-compatible with the MAX824 family per onsemi's datasheet Feature list and Pin Connections diagram. Both use identical TSOT-23-5 pinout (VCC, WDI, RESET, GND, RESET) and share matching electrical timing (e.g., 140 ms min reset timeout, 1.12 s min watchdog period). This compatibility allows drop-in replacement in existing MAX824 designs without PCB modification - confirmed in the official CAT823/CAT824 datasheet Section "Pin and Function Compatible with the MAX823/24 Products".