onsemi CAT825RSDI-GT3

Overview

CAT825RSDI-GT3 from onsemi is a system supervisory voltage reset IC with watchdog timer and manual reset input, designed for brownout detection and power-on reset in low-voltage embedded systems. It features a 2.63 V reset threshold, 140–400 ms reset timeout, 1.12–3.20 s watchdog timeout, TSOT-23-5 package, and operates across −40°C to +85°C. It is used in microcontroller-based portable equipment requiring reliable power sequencing and fault recovery.

For engineers reviewing the CAT825RSDI-GT3 datasheet, pinout, applications, or equivalent options, key selection criteria include reset threshold accuracy (±2.5% over temperature), MR input pull-up resistance (52 kΩ), WDI pulse width tolerance (50 ns min), push-pull RESET output drive capability (1.2 mA sink at 2.55 V), and compatibility with 2.0–3.6 V supply rails.

Technical Context

The CAT825RSDI-GT3 implements a precision bandgap-based voltage reference with 40 ppm/°C tempco and internal hysteresis (5 mV) to ensure stable brownout detection during supply transients. Its digital delay block enforces a minimum 140 ms reset assertion after VCC exceeds VRST, independent of supply ramp rate.

Watchdog functionality uses an edge-triggered monostable circuit that resets on any WDI transition (low-to-high or high-to-low) within a 1.12–3.20 s window; timeout initiates a full reset cycle. The MR input includes internal debouncing and 5 µs noise immunity filtering, with 1 s minimum pulse width support and 5 µs delay from MR release to RESET activation.

Key Specifications

Pinout & Package

Package: TSOT-23-5 (Case 419AE), 2.90 mm × 1.60 mm × 0.95 mm profile, RoHS-compliant NiPdAu finish, tape-and-reel packaging (3,000 pcs/reel).

Key Features

Applications

Equivalent & Alternatives

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

Compared with CAT825RSDI-GT3, MAX823RCSA+T omits watchdog capability but offers identical reset accuracy and pinout for legacy drop-in replacement where supervision is limited to power monitoring; TPS3808G12DBVR provides broader timeout flexibility and lower operating voltage support but requires layout adjustment for its different threshold and higher quiescent current.

Availability

CAT825RSDI-GT3 is available at Aetrix Electronics and suitable for industrial sensor nodes, wearable health monitors, smart home controllers, POS terminal peripherals, and battery-backed real-time clock modules requiring stable component supply and long-term lifecycle assurance.

Supply support for CAT825RSDI-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 silicon solutions for automotive, industrial, cloud, medical, and IoT applications.

The CAT82x series is part of onsemi's system supervision product line, engineered specifically for reliable power-on reset, brownout protection, and firmware watchdog functions in space-constrained, low-power embedded systems.

FAQ

What is the exact reset threshold voltage of CAT825RSDI-GT3 and how does it vary with temperature?

The CAT825RSDI-GT3 has a nominal reset threshold of 2.63 V, with guaranteed limits of 2.55 V (min) and 2.70 V (max) across −40°C to +85°C. Its temperature coefficient is 40 ppm/°C, meaning threshold drift is ≤ ±0.0105 V over the full range - sufficient for stable operation in unregulated battery-powered systems without external trimming.

Does CAT825RSDI-GT3 support manual reset initiation, and what are the electrical requirements for the MR pin?

Yes, CAT825RSDI-GT3 supports manual reset via its MR pin, which is internally pulled up to VCC with a 52 kΩ resistor. To assert reset, MR must be driven below 0.3 × VCC for ≥1 µs; the device includes 100 ns noise immunity and debounces pulses shorter than that. Release of MR triggers a 5 µs delay before RESET activates, followed by the full 140–400 ms timeout period.

Can CAT825RSDI-GT3 be used with a 2.0 V supply, and what is its minimum functional VCC?

Yes, CAT825RSDI-GT3 is fully specified for operation from 2.0 V to 3.6 V. Its RESET output remains valid down to VCC = 1.0 V, and internal circuitry functions correctly at 2.0 V - making it suitable for single-cell LiFePO₄ (2.0–3.6 V) and alkaline battery (2.0–3.2 V) applications where other reset ICs may fail to assert reliably.

How does the watchdog timer in CAT825RSDI-GT3 behave when the WDI input is left floating?

When WDI is left floating or tri-stated, CAT825RSDI-GT3 detects the open condition and automatically disables the watchdog function. It then cycles WDI low for 7/8 of the timeout period (≈0.98–2.8 s) and high for 1/8 (≈0.14–0.4 s), repeating indefinitely. This behavior prevents unintended resets while signaling that watchdog supervision is inactive - no external pull-up/down is needed.

Is CAT825RSDI-GT3 pin-compatible with other devices in the CAT82x family, and what are the key functional differences?

CAT825RSDI-GT3 shares the same TSOT-23-5 pinout as CAT823RTDI-GT3 and CAT824 variants, but differs functionally: CAT825RSDI-GT3 is a CAT823 variant (includes MR input), not CAT824 (dual RESET outputs). It is pin-compatible with CAT823RTDI-GT3, differing only in marking and date code; both provide MR, WDI, and single active-low RESET in identical package and electrical specs.