Texas Instruments TPS3705-33DGN

Overview

TPS3705-33DGN from Texas Instruments is a precision 3.3 V supply-voltage supervisor IC with integrated watchdog timer, power-fail comparator, and 200 ms fixed-reset delay. It monitors VDD ≥ 1.1 V, asserts active-low RESET on undervoltage or power-fail events, and supports manual reset via MR pin. Designed for microcontroller-based systems requiring reliable power sequencing and fault detection in industrial and automotive environments.

For engineers reviewing the TPS3705-33DGN datasheet, TPS3705-33DGN pinout, TPS3705-33DGN application, or TPS3705-33DGN equivalent, key selection criteria include its –40°C to 125°C operating range, 2.93 V threshold with 50 mV hysteresis, 50 µA max supply current, watchdog timeout of 1.6 s, and compatibility with MSP430 and similar low-power processors.

Technical Context

The TPS3705-33DGN implements dual supervision: a precision bandgap-referenced VDD monitor with fixed 2.93 V negative-going threshold (VIT–) and 50 mV hysteresis, plus an independent PFI/PFO comparator for secondary rail monitoring. Its internal watchdog timer requires periodic WDI transitions and triggers WDO after 1.1–2.3 s timeout if unrefreshed.

It operates across 2 V to 6 V supply, delivers RESET with 3–5 µs propagation delay from VDD, and uses no external capacitor for reset timing. The device features separate MR input for system-initiated reset and supports both active-low RESET output and open-drain WDO/PFO outputs.

Key Specifications

Pinout & Package

TPS3705-33DGN is housed in an 8-pin MSOP-PowerPAD™ package (3.00 mm × 3.00 mm body), featuring exposed thermal pad for improved heat dissipation in high-density PCB layouts.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar voltage supervision and watchdog applications.

Compared with TPS3705-33D and MAX706TSA+, the TPS3705-33DGN uniquely combines extended temperature operation (–40°C to 125°C), integrated watchdog, and MSOP-PowerPAD thermal efficiency-making it optimal for next-generation automotive and industrial edge devices where reliability and density are critical.

Availability

TPS3705-33DGN is available at Aetrix Electronics and suitable for industrial PLC controllers, automotive body control modules, portable medical monitors, and smart energy meters requiring stable component supply and long-term lifecycle support.

Supply support for TPS3705-33DGN 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 TPS370x family was designed specifically for robust power-supply supervision in microprocessor-based systems-emphasizing precision threshold accuracy, low quiescent current, and integrated fault-detection features like watchdog and power-fail warning.

FAQ

What is the exact reset threshold voltage for TPS3705-33DGN across its full temperature range?

The TPS3705-33DGN has a nominal VDD negative-going threshold (VIT–) of 2.93 V, with guaranteed min/max of 2.87 V to 3.02 V over –40°C to 125°C. This is specified in Section 7.6 of the datasheet and confirmed by histogram data showing tight distribution at all three test temperatures (–40°C, 25°C, 125°C). The 50 mV hysteresis ensures noise immunity during threshold crossing.

Does TPS3705-33DGN require an external capacitor for its 200 ms reset delay function?

No, the TPS3705-33DGN integrates a precision internal timing circuit that delivers a fixed 200 ms reset delay without any external capacitor. This is explicitly stated in the Features section and verified in the Timing Requirements table (td = 140–280 ms). External capacitors are only needed for decoupling (0.1 µF recommended near VDD/GND).

How does the watchdog timer in TPS3705-33DGN behave if the WDI pin is left unconnected?

If the WDI pin is left unconnected (floating), the watchdog timer in the TPS3705-33DGN is automatically disabled, and WDO remains high-impedance. This behavior is documented in Section 8.3.3: "Leaving WDI unconnected disables the watchdog." No external pull-up or pull-down is required to disable the function.

Can TPS3705-33DGN monitor a 5 V supply rail, or is it limited to 3.3 V systems?

The TPS3705-33DGN is optimized for 3.3 V VDD supervision (2.93 V threshold), but its PFI input can monitor any secondary rail-including 5 V-using an external resistor divider. As shown in Figure 9-1 and Equation 1, scaling a 5 V rail down to ~1.25 V at PFI enables precise power-fail detection while VDD supervision remains dedicated to the 3.3 V domain.

What is the thermal performance advantage of the MSOP-PowerPAD package used by TPS3705-33DGN?

The MSOP-PowerPAD™ package of the TPS3705-33DGN achieves RθJA = 66.1°C/W, significantly lower than the SOIC version's 118.2°C/W. This 44% improvement in junction-to-ambient thermal resistance-enabled by the exposed thermal pad-allows higher power dissipation or operation in hotter ambient environments without exceeding maximum junction temperature limits.