Texas Instruments UCC3946DTR

Overview

UCC3946DTR 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), operating from 2 V to 5.5 V supply and supporting industrial temperature range (0°C to 70°C). It ensures reliable power-on reset and fault detection in embedded control systems.

For engineers reviewing the UCC3946DTR datasheet, UCC3946DTR pinout, UCC3946DTR application, or UCC3946DTR equivalent, key selection criteria include its 1 V minimum valid reset voltage, 18 µA max supply current, glitch-immune RTH input, independent RES/WDO outputs, and TSSOP-8 package compatibility with space-constrained PCB layouts.

Technical Context

The UCC3946DTR implements dual independent timing blocks: a precision power-on reset circuit with 400 nA current source charging CRP for reset period control, and an edge-detecting watchdog timer with 25×CWP scaling. Its internal 1.235 V reference enables accurate threshold programming via external resistive dividers on RTH.

Reset assertion remains valid down to VDD = 1 V, and the device ignores transients below 100 mV overdrive or shorter than 120 µs (per Figure 1), ensuring immunity to supply rail noise. Watchdog disable during reset prevents spurious timeouts, and WDO output is actively driven low upon timeout with guaranteed 50 ns pulse width.

Key Specifications

Pinout & Package

UCC3946DTR is packaged in an 8-pin TSSOP (PW) with 0.65 mm pitch, optimized for high-density PCB layouts and automated assembly. Thermal performance meets industrial requirements with θ_JA ≈ 160°C/W.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MAX6816EPA+ and TPS3808G33DBVR, the UCC3946DTR uniquely combines full programmability of both reset and watchdog thresholds/timing with 1 V valid reset operation - enabling single-chip supervision across variable-voltage, safety-critical, and resource-constrained embedded designs.

Availability

UCC3946DTR is available at Aetrix Electronics and suitable for industrial PLC controllers, medical infusion pumps, smart energy meters, and automotive body control modules requiring stable component supply, long-term lifecycle support, and consistent parametric performance across production batches.

Supply support for UCC3946DTR 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 UCC3946DTR belongs to TI's legacy microprocessor supervisor family, designed specifically for robust, low-power, programmable reset and watchdog supervision in harsh industrial environments where voltage stability and fault detection reliability are critical.

FAQ

What is the minimum supply voltage at which UCC3946DTR guarantees valid reset assertion?

The UCC3946DTR guarantees valid reset assertion down to 1 V on VDD, as specified in the Electrical Characteristics table under "Minimum VDD (Note 1)". This ensures fail-safe behavior during deep brownout conditions where other supervisors may lose functionality. The RES output remains asserted low until VDD rises above the programmed reset threshold and remains stable for the full reset period. This 1 V capability is a key differentiator of the UCC3946DTR versus many fixed-threshold supervisors.

How do I program the reset threshold for UCC3946DTR using external resistors?

To program the reset threshold for UCC3946DTR, connect a resistor divider between VDD and GND, with the midpoint feeding the RTH pin. The threshold voltage is calculated as V_RESET = 1.235 V × (R1 + R2)/R2, where R1 connects to VDD and R2 to GND. Use high-value resistors (e.g., 1 MΩ–10 MΩ) to minimize current draw. The UCC3946DTR's 5 nA RTH input leakage ensures accuracy is preserved across the full industrial temperature range.

Can UCC3946DTR's RES and WDO outputs be directly wired together?

Yes, UCC3946DTR's RES and WDO outputs can be directly wired together, but only if the application tolerates increased current flow during conflicting drive states (e.g., RES high while WDO low). In that case, the low output dominates, sinking current from VDD through the high-side driver. For robust designs, TI recommends connecting RES and WDO to separate inputs or using an external OR gate. Direct tieing is acceptable in cost-sensitive, non-safety-critical applications where transient current spikes are acceptable.

What capacitor type is recommended for RP and WP pins on UCC3946DTR?

For RP and WP pins on UCC3946DTR, NPO (C0G) ceramic capacitors are strongly recommended due to their low leakage, tight tolerance (±5%), and near-zero voltage coefficient. These characteristics preserve timing accuracy across temperature and voltage, especially critical for the 400 nA current source driving RP. Avoid X7R or Y5V types, whose leakage and capacitance drift degrade reset and watchdog period consistency. Mount capacitors with minimal trace length to reduce stray capacitance and noise coupling.

Does UCC3946DTR support operation at extended temperature ranges beyond 0°C to 70°C?

No, the UCC3946DTR is specified only for operation from 0°C to 70°C ambient temperature, as stated in the Electrical Characteristics table. While the absolute maximum junction temperature is +150°C, the parametric performance (e.g., reset threshold accuracy, timing tolerances, supply current) is guaranteed only within the 0°C to 70°C range. For extended temperature applications, consider the UCC2946 (–40°C to 95°C) or UCC1946 (–55°C to 125°C), which share identical pinout and functionality but differ in qualification and characterization.