Texas Instruments UCC3946NG4

Overview

UCC3946NG4 from Texas Instruments is a microprocessor supervisor IC with integrated watchdog timer, programmable reset threshold (1.235 V ±2%), programmable reset period (160–260 ms with 64 nF), and programmable watchdog period (1.12–2.08 s with 64 nF). It operates from 2 V to 5.5 V, draws ≤18 µA supply current, and asserts valid reset down to VDD = 1 V - used in embedded systems requiring reliable power-on and fault recovery.

For engineers reviewing the UCC3946NG4 datasheet, UCC3946NG4 pinout, UCC3946NG4 application, or UCC3946NG4 equivalent, key selection criteria include its 2% accurate reset threshold, glitch-immune reset detection, independent RES/WDO outputs, low-voltage operation capability, and external capacitor-based timing programming for both reset and watchdog functions.

Technical Context

The UCC3946NG4 implements dual independent timing paths: one for power-on reset (POR) using a precision 400 nA current source charging CRP on RP pin, and another for watchdog timeout using a 25× scaling current source charging CWP on WP pin. Both thresholds reference an internal 1.235 V bandgap.

Its reset logic includes hysteresis (15 mV), voltage glitch filtering per Figure 1, and guaranteed RES assertion at VDD ≥1 V. The WDO output is active-low, disabled during reset, and reinitiated upon RES deassertion - ensuring clean separation between power-fault and software-fault responses.

Key Specifications

Pinout & Package

UCC3946NG4 is packaged in an 8-pin PDIP (N package), with lead finish Sn/Pb and RoHS non-compliant marking per TI's legacy part definition. Pinout matches SOIC-8 and TSSOP-8 variants electrically.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar microprocessor supervision applications.

Compared with MAX6816ESA+ and TPS3808G33DBVR, the UCC3946NG4 uniquely combines fully programmable reset voltage, independently programmable reset and watchdog periods, and sub-1 V reset validity - making it optimal for multi-rail or legacy voltage systems requiring design flexibility and robust fault coverage.

Availability

UCC3946NG4 is available at Aetrix Electronics and suitable for industrial PLC controllers, medical infusion pumps, telecom remote terminal units, and automotive body control modules requiring stable component supply and long-term lifecycle support.

Supply support for UCC3946NG4 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 company headquartered in Dallas, TX, delivering analog and embedded processing solutions across industrial, automotive, and personal electronics markets.

The UCC3946NG4 belongs to TI's legacy microprocessor supervisor family designed for high-reliability embedded systems requiring deterministic reset behavior, glitch immunity, and flexible timing configuration without internal oscillators.

FAQ

What is the minimum supply voltage at which UCC3946NG4 guarantees valid reset output?

The UCC3946NG4 guarantees valid RES assertion down to VDD = 1 V, as confirmed in the Electrical Characteristics table (Note 1) and Description section. This means that even during deep brownout conditions, the UCC3946NG4 will hold the microprocessor in reset until the supply recovers above the programmed threshold. This feature is critical for systems where partial power loss could corrupt memory or cause unsafe actuator movement. The UCC3946NG4 achieves this with internal low-voltage biasing and a dedicated 1 V validation path distinct from normal operation.

How does UCC3946NG4 handle voltage glitches on the VDD line?

The UCC3946NG4 filters VDD glitches using a built-in hysteresis and time-duration threshold defined in Figure 1 of the datasheet. Glitches less than ~100 mV in amplitude and shorter than ~120 µs are ignored at the RTH pin, preventing false resets. This behavior is implemented via analog filtering on the internal comparator input and is guaranteed by design. The UCC3946NG4 does not rely on digital debouncing; instead, its analog response ensures immunity to fast transients common in switching power supplies or relay-driven loads - a key differentiator from basic reset ICs.

Can UCC3946NG4 monitor a voltage other than VDD for reset purposes?

Yes, the UCC3946NG4 can monitor any external voltage via the RTH pin using a resistor divider, as explicitly described in the "Programming the Reset Voltage" section. The internal 1.235 V reference compares against the divided voltage, enabling supervision of 1.8 V, 2.5 V, 3.3 V, or 5 V rails - or even battery voltage - independent of VDD. This capability is confirmed in the Application Diagram (Figure 4) and PIN DESCRIPTIONS. For example, R1 and R2 can be selected so that RTH = 1.235 V when the monitored rail reaches the desired trip point, giving full design flexibility beyond VDD tracking.

What is the function of the WP and RP pins on UCC3946NG4?

The RP pin connects to an external capacitor (CRP) and sources a precision 400 nA current to set the reset period (TRP = 3.125 × CRP in ms). The WP pin connects to another external capacitor (CWP) and sources a 25× scaled current to set the watchdog period (TWP = 25 × CWP in ms). Both pins enable accurate, temperature-stable timing without crystals or RC networks prone to drift. These functions are detailed in the APPLICATION INFORMATION section and verified in the Electrical Characteristics table under "Reset Period" and "Watchdog Period" rows. Neither pin is a digital control input - they are analog timing terminals requiring low-leakage NP0/C0G capacitors.

Is UCC3946NG4 pin-compatible with UCC2946NG4 or UCC1946NG4?

No, UCC3946NG4 is not pin-compatible with UCC2946NG4 or UCC1946NG4 in terms of temperature grade or absolute maximum ratings, though all three share identical pinout, package options (SOIC-8/DIP-8/TSSOP-8), and functional block diagram. The UCC3946NG4 is rated for 0°C to 70°C operation, while UCC2946NG4 supports −40°C to 95°C and UCC1946NG4 covers −55°C to 125°C. Electrical parameters such as minimum VDD (1 V vs. 1.1 V) and operating voltage range (2 V–5.5 V vs. 2.1 V–5.5 V) also differ. Therefore, direct substitution requires thermal and electrical validation per application environment.