Texas Instruments TPS3705-33DGNR

Overview

TPS3705-33DGNR 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, and supports manual reset via MR pin. Used in microcontroller-based systems requiring reliable power sequencing and fault detection.

For engineers reviewing the TPS3705-33DGNR datasheet, TPS3705-33DGNR pinout, TPS3705-33DGNR application, or TPS3705-33DGNR equivalent, key selection criteria include its –40°C to 125°C extended temperature rating, 2.93 V VIT– threshold with 50 mV hysteresis, 1.6 s watchdog timeout, 50 µA max supply current, and MSOP-PowerPAD (8) package compatibility with space-constrained industrial and automotive designs.

Technical Context

The TPS3705-33DGNR implements dual supervision: a precision bandgap-referenced comparator for VDD monitoring (2.93 V ±30 mV over –40°C to 125°C) and a separate PFI/PFO path for auxiliary rail or battery voltage monitoring (1.25 V threshold). Its internal oscillator drives a watchdog timer with 1.1–2.3 s timeout, retriggerable via WDI transitions.

Reset assertion logic combines power-on initialization (RESET active until VDD > 1.1 V), undervoltage detection (RESET low when VDD < VIT–), and manual override (MR low forces RESET low). All functions operate without external capacitors, and outputs are push-pull with 1 mA sink capability and 0.3 V VOL at VDD = 3.2 V.

Key Specifications

Pinout & Package

TPS3705-33DGNR uses an 8-pin MSOP-PowerPAD package with exposed thermal pad (3.00 mm × 3.00 mm body size). The PowerPAD improves thermal dissipation and requires soldering to PCB ground plane for optimal performance.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar voltage supervisor applications.

Compared with TPS3705-33DR, the TPS3705-33DGNR offers superior thermal performance and smaller footprint for dense PCBs; compared with MAX6326LT33D3+T, it adds watchdog and PFI functionality at higher quiescent current, enabling more robust system-level fault handling.

Availability

TPS3705-33DGNR is available at Aetrix Electronics and suitable for industrial PLC control, automotive body electronics, portable medical monitors, and smart energy metering requiring stable component supply across extended temperature ranges.

Supply support for TPS3705-33DGNR 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 delivering analog and embedded processing solutions for industrial, automotive, and personal electronics markets.

The TPS370x family is designed for microprocessor and DSP power-supply supervision, integrating reset generation, power-fail detection, and watchdog functionality in compact packages for mission-critical embedded systems.

FAQ

What is the exact V_IT– threshold voltage for TPS3705-33DGNR over its full temperature range?

The TPS3705-33DGNR has a nominal V_IT– threshold of 2.93 V, specified from –40°C to 125°C with min/max values of 2.87 V and 3.02 V respectively. This 50 mV hysteresis ensures clean, noise-immune reset assertion during 3.3 V rail transitions. The value is factory-trimmed and does not require external calibration. TPS3705-33DGNR maintains this specification across its entire qualified operating temperature range.

Does TPS3705-33DGNR require an external capacitor for reset timing?

No, TPS3705-33DGNR features an internal 200 ms reset delay timer that requires no external capacitor. This eliminates timing component variation, reduces bill-of-materials count, and improves long-term reliability versus RC-based solutions. The fixed delay is guaranteed across –40°C to 125°C and independent of supply voltage within 2–6 V. TPS3705-33DGNR achieves this using trimmed on-chip RC elements.

How does the watchdog function operate in TPS3705-33DGNR?

The TPS3705-33DGNR watchdog timer times out after 1.6 s (1.1–2.3 s range) if WDI receives no edge transition. A rising or falling edge on WDI resets the timer. Upon timeout, WDO asserts low and internally reinitializes. Leaving WDI unconnected disables the watchdog. TPS3705-33DGNR's watchdog is fully integrated-no external components needed-and operates independently of VDD supervision.

Can TPS3705-33DGNR monitor a secondary voltage rail like a battery supply?

Yes, TPS3705-33DGNR includes a dedicated PFI (power-fail input) pin that monitors auxiliary voltages down to 1.25 V with 10 mV hysteresis. When PFI falls below threshold, PFO asserts low to signal battery depletion or secondary supply failure. This function operates concurrently with VDD supervision and requires no additional ICs. TPS3705-33DGNR thus provides dual-rail monitoring in a single 3 mm × 3 mm package.

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

TPS3705-33DGNR's MSOP-PowerPAD package delivers RθJA = 66.1°C/W, significantly lower than the SOIC-8 variant's 118.2°C/W. The exposed thermal pad must be soldered to a PCB ground plane to achieve this rating, enabling higher power dissipation (1.37 W at 70°C ambient) and improved reliability in thermally demanding environments. This makes TPS3705-33DGNR suitable for compact, high-density industrial and automotive PCBs where thermal management is critical.