Texas Instruments UCC2946D

Overview

UCC2946 from Texas Instruments is a microprocessor supervisor IC with integrated watchdog timer, programmable reset threshold (1.235 V ±2%), programmable reset period (140–320 ms), and programmable watchdog period (0.96–2.56 s). It operates from 2.1 V to 5.5 V, draws ≤18 µA supply current, and asserts valid reset down to VDD = 1.1 V - ideal for industrial embedded systems requiring reliable power-on and fault recovery.

For engineers reviewing the UCC2946 datasheet, UCC2946 pinout, UCC2946 application, or UCC2946 equivalent, key selection considerations include its –40°C to +95°C operating temperature range, independent RES and WDO outputs, precision 400 nA timing current sources, and external capacitor-based programming of both reset and watchdog timing.

Technical Context

The UCC2946 implements dual independent timing paths: one for power-on reset using a 400 nA current source charging CRP on RP pin (TRP = 3.125 × CRP ms), and another for watchdog timeout using identical 400 nA sourcing on WP pin (TWP = 25 × CWP ms). Both thresholds reference an internal 1.235 V bandgap.

Its reset logic features glitch immunity via voltage-duration filtering at RTH (100 mV overdrive triggers ~120 µs delay), hysteresis (15 mV), and guaranteed RES assertion at VDD ≥ 1.1 V. Watchdog function disables during active reset and requires edge-triggered WDI toggling to prevent WDO assertion.

Key Specifications

Pinout & Package

UCC2946 is packaged in 8-pin SOIC (D), 8-pin TSSOP (PW), and 8-pin PDIP (N/J) - all pin-compatible with identical pin mapping.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar microprocessor supervisor with watchdog applications.

Compared with MAX6326UT46D3+ and TPS3808G33DBVR, the UCC2946 uniquely supports full analog programmability of both reset threshold and timing intervals via external resistors and capacitors - enabling precise adaptation to diverse supply rails and system boot/fault-response requirements without redesign.

Availability

UCC2946 is available at Aetrix Electronics and suitable for industrial automation, smart metering, and factory HMI applications requiring stable component supply, long-term lifecycle support, and guaranteed performance across extended temperature ranges.

Supply support for UCC2946 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

Texas Instruments is a global semiconductor leader delivering analog, embedded processing, and connectivity solutions for industrial, automotive, and personal electronics markets.

The UCC2946 belongs to TI's microprocessor supervisor product line, designed specifically for robust, programmable power monitoring and fault recovery in harsh industrial environments where reliability and configurability are critical.

FAQ

What is the minimum supply voltage at which UCC2946 guarantees valid reset output?

The UCC2946 guarantees valid RES assertion down to VDD = 1.1 V, as specified in the Absolute Maximum Ratings and Electrical Characteristics tables. This ensures reliable reset behavior even during deep brownout conditions or battery backup scenarios where VDD drops below nominal levels. The UCC2946 maintains this capability across its full –40°C to +95°C operating temperature range.

How does UCC2946 implement glitch immunity on the reset input?

The UCC2946 achieves glitch immunity through analog filtering at the RTH pin: voltage excursions less than 100 mV above the 1.235 V threshold are ignored unless sustained for ≥120 µs. This behavior is characterized in Figure 1 of the datasheet and ensures RES remains deasserted during fast transients, preventing spurious resets caused by switching noise or ESD coupling on the monitored rail.

Can UCC2946 monitor a voltage other than VDD for reset purposes?

Yes - the UCC2946 uses the RTH pin as a high-impedance input referenced to an internal 1.235 V bandgap, allowing it to monitor any DC voltage rail via an external resistor divider. For example, a 12 V rail can be scaled to 1.235 V using R1 = 8.7 MΩ and R2 = 1 MΩ. This flexibility makes UCC2946 suitable for multi-rail systems where core, I/O, or analog supplies require independent supervision.

What capacitor type is recommended for RP and WP pins on UCC2946?

NPO (C0G) ceramic capacitors are explicitly recommended for CRP and CWP due to their low leakage, tight tolerance, and minimal capacitance drift over temperature and voltage. These characteristics preserve timing accuracy of the 400 nA current-source-based TRP and TWP calculations. X7R or Y5V types are discouraged because their higher leakage and voltage coefficient degrade timing stability.

Does UCC2946 support connecting WDO directly to RES for combined reset generation?

Yes - the UCC2946 allows direct connection of WDO to RES since both are open-drain outputs. During normal operation, RES is pulled high by an external pull-up while WDO remains high; if WDO asserts low, it dominates and pulls RES low. However, this configuration increases current draw during fault states, so designers should verify that the combined sink current (up to 2 mA) remains within VDD supply capability and thermal limits.