Texas Instruments TPS3305-33DR

Overview

TPS3305-33DR from Texas Instruments is a dual-voltage supervisor IC designed for DSP- and processor-based systems requiring independent monitoring of 5.0 V and 3.3 V rails. It provides power-on reset with 200 ms fixed delay, watchdog timer timeout of 1.6 s (typ), and operates from 2.7 V to 6 V supply. It asserts active-low and active-high RESET outputs when either SENSE1 or SENSE2 falls below its threshold (4.55 V / 2.93 V typ) or WDI stalls - used in industrial control and embedded computing.

For engineers reviewing the TPS3305-33DR datasheet, TPS3305-33DR pinout, TPS3305-33DR application, or TPS3305-33DR equivalent, key selection criteria include dual-supply threshold accuracy (±1.5% over temperature), micropower operation (40 µA max), guaranteed RESET assertion down to VDD ≥1.1 V, and SOIC-8 package compatibility with legacy board layouts.

Technical Context

The TPS3305-33DR implements two independent voltage-sense comparators with hysteresis (30–40 mV), a precision 1.25 V internal reference, and a watchdog timer with 1.6 s typical timeout. Its logic combines SENSE1/SENSE2 status and WDI activity to drive complementary RESET outputs.

Reset assertion is triggered by undervoltage on either SENSE input (VIT− = 4.46 V / 2.86 V min at −40°C to +85°C), MR pin low, or WDI inactivity beyond timeout. After recovery, a factory-programmed 200 ms (140–280 ms) delay ensures stable system initialization before deasserting RESET.

Key Specifications

Pinout & Package

TPS3305-33DR is housed in an 8-pin SOIC (D) package, 3.9 mm × 4.9 mm, 1.75 mm max height, RoHS-compliant with NiPdAu lead finish and MSL Level-1 rating.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar dual-supply supervisory applications.

Compared with TPS3305-33DGN, the TPS3305-33DR offers identical supervision functionality in a larger SOIC-8 package that simplifies hand-soldering and legacy board reuse; versus MAX6816EPA+, it adds critical dual-rail monitoring and watchdog capability essential for complex DSP-based systems.

Availability

TPS3305-33DR is available at Aetrix Electronics and suitable for industrial PLC controllers, automotive infotainment systems, and network edge routers requiring stable component supply with full traceability and long-term lifecycle support.

Supply support for TPS3305-33DR 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 specializing in analog, embedded processing, and connectivity technologies with over 50 years of innovation in power management and system supervision ICs.

The TPS3305 family was engineered specifically for dual-rail DSP and microprocessor systems needing coordinated reset sequencing, watchdog safety, and micropower operation across harsh industrial and automotive environments.

FAQ

What are the exact voltage thresholds monitored by the TPS3305-33DR?

The TPS3305-33DR monitors SENSE1 at a nominal 5.0 V rail with a typical threshold of 4.55 V (min 4.46 V, max 4.67 V over −40°C to +85°C) and SENSE2 at a nominal 3.3 V rail with a typical threshold of 2.93 V (min 2.86 V, max 3.02 V). These thresholds include built-in hysteresis of 30–40 mV to prevent oscillation near trip points. The TPS3305-33DR uses an internal temperature-compensated 1.25 V reference to maintain accuracy across its full operating range.

Does the TPS3305-33DR require external capacitors for reset timing?

No, the TPS3305-33DR does not require external capacitors for its power-on reset delay. It features a factory-programmed 200 ms (140–280 ms) fixed delay time implemented internally, eliminating the need for timing capacitors and reducing component count. However, a 0.1 µF ceramic bypass capacitor is recommended close to the VDD and GND pins to stabilize the internal reference and improve noise immunity - this is explicitly noted in the datasheet for optimal threshold stability.

How does the watchdog function operate on the TPS3305-33DR?

The watchdog timer in the TPS3305-33DR monitors the WDI (Watchdog Input) pin: if WDI remains static (high or low) for longer than 1.6 s (1.1–2.3 s over temperature), the device asserts both RESET outputs. Toggling WDI at any frequency faster than this timeout resets the internal watchdog counter. The TPS3305-33DR does not require clock configuration - its oscillator and timing are fully integrated. This behavior is independent of SENSE1/SENSE2 status and provides autonomous firmware health checking.

Can the TPS3305-33DR be used with supply voltages below 3.3 V?

Yes, the TPS3305-33DR operates from 2.7 V to 6.0 V on VDD and maintains defined RESET output behavior down to VDD = 1.1 V. Its internal circuitry - including comparators and reference - remains functional across the full 2.7–6.0 V range. Below 2.7 V, the device may not meet all specifications, but the guaranteed RESET assertion down to 1.1 V ensures fail-safe behavior during brownout conditions where other supervisors might release prematurely. This makes the TPS3305-33DR suitable for systems with wide-input DC-DC converters.

What is the difference between the RESET and RESET pins on the TPS3305-33DR?

The TPS3305-33DR provides two complementary reset outputs: Pin 5 (RESET) is an active-low open-drain output requiring an external pull-up resistor to define its high state and interface with various logic families; Pin 6 (RESET) is an active-high push-pull output capable of directly driving CMOS/TTL inputs without external components. Both outputs assert simultaneously during any fault condition (SENSE undervoltage, WDI timeout, or MR assertion) and deassert together after the 200 ms delay. This dual-output architecture increases design flexibility across host system interface requirements.