Texas Instruments UCC2946PWTR

Overview

UCC2946PWTR 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 - used in industrial embedded systems requiring reliable power-on and fault recovery.

For engineers reviewing the UCC2946PWTR datasheet, UCC2946PWTR pinout, UCC2946PWTR application, or UCC2946PWTR equivalent, key selection criteria include its −40°C to +95°C operating temperature range, TSSOP-8 package compatibility, dual programmability of reset and watchdog timing via external capacitors, and guaranteed reset validity at low VDD for brownout resilience.

Technical Context

The UCC2946PWTR implements independent analog voltage monitoring and digital edge-triggered watchdog logic. Its RTH pin compares external resistor-divider voltage against an internal 1.235 V reference with 15 mV hysteresis, while RP and WP pins each sink a precision 400 nA current to charge external timing capacitors for reset and watchdog periods respectively.

Reset assertion is voltage- and time-conditioned: RES remains low until VDD exceeds the programmed threshold and stays above it for the full TRP duration; transient glitches below defined overdrive/delay thresholds (per Figure 1) are rejected. WDO assertion is strictly edge-sensitive on WDI - no toggle within TWP causes immediate low output, disabled only during active reset.

Key Specifications

Pinout & Package

UCC2946PWTR is housed in an 8-pin TSSOP (PW) package - 3.0 mm × 4.4 mm, 0.65 mm pitch, surface-mount, lead-free compatible.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MAX692AESA+ and TPS3808G33DBVR, the UCC2946PWTR uniquely supports full analog threshold programming across 1.2–5 V rails, dual independent timing capacitors, and guaranteed reset validity below 1.2 V - making it the only option for multi-rail brownout resilience with adaptive watchdog coverage.

Availability

UCC2946PWTR is available at Aetrix Electronics and suitable for industrial control systems, smart energy meters, motor drive controllers, and factory automation HMIs requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for UCC2946PWTR 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, Texas, delivering analog and embedded processing solutions for industrial, automotive, and personal electronics markets.

The UCC2946PWTR belongs to TI's legacy microprocessor supervisor family - designed specifically for high-reliability industrial systems where programmable reset and watchdog timing, low-voltage operation, and noise immunity are critical.

FAQ

What is the minimum VDD voltage at which UCC2946PWTR guarantees valid reset output?

The UCC2946PWTR guarantees valid reset output (RES) down to VDD = 1.1 V, as specified in the Electrical Characteristics table under "Minimum VDD (Note 1)". Below this, RES behavior is not characterized. This ensures deterministic reset assertion during severe brownout conditions where other supervisors may fail silently. The UCC2946PWTR achieves this via optimized internal biasing and low-threshold comparators - a key differentiator versus fixed-threshold alternatives.

How does the UCC2946PWTR reject power-supply glitches?

The UCC2946PWTR rejects glitches using a voltage-time filter on the RTH pin, defined by Figure 1 in the datasheet: transients with overdrive <100 mV above threshold or duration <120 µs are ignored. This is implemented via internal RC filtering and edge-detection logic - not simple hysteresis. As a result, the UCC2946PWTR maintains RES high during fast spikes common in motor drives or switch-mode supplies, preventing false resets. This behavior is confirmed across its −40°C to +95°C operating range.

Can UCC2946PWTR monitor a voltage rail other than VDD?

Yes - the UCC2946PWTR can monitor any DC voltage rail via the RTH pin, using an external resistor divider to scale the target voltage to match its internal 1.235 V reference. For example, a 12 V rail can be monitored by setting R1/R2 = 8.75:1. This capability is explicitly supported in the "Programming the Reset Voltage" section and distinguishes UCC2946PWTR from fixed-input supervisors. The UCC2946PWTR's high-impedance RTH input (5 nA leakage) ensures minimal loading on the sensed rail.

What capacitor types are recommended for RP and WP pins on UCC2946PWTR?

Texas Instruments specifies NPO (C0G) ceramic capacitors for both RP and WP pins due to their low leakage (<10 pA), tight tolerance (±5%), and near-zero voltage coefficient - essential for maintaining timing accuracy across temperature and voltage. X7R or Y5V types are discouraged because their leakage and capacitance drift degrade TRP and TWP stability. The UCC2946PWTR's 400 nA precision current source demands minimal parasitic discharge; layout best practices also require short traces and local 0.1 µF VDD decoupling.

Does UCC2946PWTR support connecting WDO directly to RES?

Yes - the UCC2946PWTR allows direct connection of WDO to RES because both outputs are open-drain and actively driven low. When WDO asserts low (watchdog timeout), it pulls RES low regardless of reset state - enabling unified reset generation. However, during simultaneous low assertions, additional current flows from VDD through pull-up resistors; TI notes this is acceptable unless system current budget is extremely tight. The UCC2946PWTR datasheet explicitly describes this configuration in "Connecting WDO to RES" (page 5).