Texas Instruments TPS3705-50DGN

Overview

TPS3705-50DGN from Texas Instruments is a precision 5-V supply voltage supervisor IC with integrated watchdog timer, power-fail comparator, and manual reset input. It provides 200-ms power-on reset delay, 4.55-V V_IT– threshold (±2.2% over –40°C to 85°C), 50 µA max supply current, and operates in 8-pin MSOP-PowerPAD™ package. It is used in microcontroller-based systems requiring reliable power sequencing and fault detection.

For engineers reviewing the TPS3705-50DGN datasheet, TPS3705-50DGN pinout, TPS3705-50DGN application, or TPS3705-50DGN equivalent, key selection criteria include its fixed 4.55-V supervision threshold, integrated watchdog timeout of 1.6 s, PFI/PFO low-battery warning capability, MR-triggered reset, and compatibility with MSP430 and other low-power processors in space-constrained industrial and portable designs.

Technical Context

The TPS3705-50DGN implements dual-supervision architecture: a precision bandgap-referenced comparator monitors V_DD against a fixed 4.55-V threshold with 70-mV hysteresis, while a separate PFI comparator detects auxiliary rail drops using an internal 1.25-V reference. Its watchdog logic responds to WDI transitions with 1.1–2.3-s timeout, and reset assertion occurs at V_DD < 1.1 V during power-up or drop-out.

It features active-low open-drain RESET output, push-pull WDO, and complementary PFO - all with sub-microsecond propagation delays (e.g., 0.5–1 µs PFI→PFO). The device requires no external capacitor for reset timing and supports operation from 2 V to 6 V across –40°C to 85°C.

Key Specifications

Pinout & Package

TPS3705-50DGN is housed in an 8-pin MSOP-PowerPAD™ package (3.00 mm × 3.00 mm body) with exposed thermal pad for improved heat dissipation. Pin 1 is RESET (active-low open-drain), Pin 2 is WDO (watchdog output), Pin 3 is MR (manual reset input), Pin 4 is V_DD, Pin 5 is GND, Pin 6 is PFI (power-fail input), Pin 7 is PFO (power-fail output), and Pin 8 is WDI (watchdog input).

Key Features

Applications

Equivalent & Alternatives

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

Compared with TPS3705-50DGN, the TPS3705-50D offers identical supervision performance in a larger SOIC package, while the MAX706CSA+ reduces power consumption but omits watchdog capability - making TPS3705-50DGN optimal for space-constrained, safety-critical embedded systems requiring autonomous fault recovery.

Availability

TPS3705-50DGN is available at Aetrix Electronics and suitable for industrial programmable controllers, portable medical devices, automotive body electronics, and wireless sensor gateways requiring stable component supply, long-term lifecycle support, and guaranteed traceable sourcing.

Supply support for TPS3705-50DGN 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 and embedded processing solutions, with deep expertise in power management, signal chain, and real-time control ICs.

The TPS370x family is designed specifically for robust microprocessor supervision in harsh environments, integrating precision voltage monitoring, power-fail warning, and watchdog functionality into compact, thermally optimized packages for industrial, automotive, and portable applications.

FAQ

What is the exact reset threshold voltage of the TPS3705-50DGN?

The TPS3705-50DGN has a nominal negative-going input threshold voltage (V_IT–) of 4.55 V, with a tolerance of ±2.2% over the full operating temperature range (–40°C to 85°C). This value is factory-trimmed and specified in Section 7.5 of the datasheet under Electrical Characteristics. The TPS3705-50DGN uses this threshold to assert RESET when the monitored 5-V supply drops below 4.55 V.

Does the TPS3705-50DGN require an external capacitor for reset timing?

No, the TPS3705-50DGN does not require an external capacitor for its 200-ms power-on reset delay. The timing is fully internal and factory-calibrated. This eliminates component count, layout area, and tolerance drift associated with external RC networks - a key differentiator from older supervisors like the MAX705 series. The TPS3705-50DGN achieves this using an on-chip oscillator and digital counter.

How is the watchdog function enabled or disabled on the TPS3705-50DGN?

The watchdog function on the TPS3705-50DGN is enabled by applying periodic rising or falling edges to the WDI (Pin 8) input. If no transition occurs within the timeout window (1.1–2.3 s), WDO (Pin 2) goes active. To disable the watchdog, WDI is left unconnected (floating) - the internal pull-down ensures it remains inactive. This behavior is explicitly documented in Section 8.3.3 and Figure 8-2 of the TPS3705-50DGN datasheet.

Can the TPS3705-50DGN monitor a 12-V rail in addition to the 5-V supply?

Yes, the TPS3705-50DGN can monitor a 12-V rail using its PFI (Pin 6) input. Since PFI compares against an internal 1.25-V reference, a resistor divider (e.g., 910 kΩ + 120 kΩ) scales the 12-V input to ~1.25 V. When the 12-V rail drops, PFI falls below 1.25 V and PFO (Pin 7) asserts. This dual-rail supervision is demonstrated in Figure 9-1 of the TPS3705-50DGN datasheet with an MSP430 application.

What is the thermal performance advantage of the MSOP-PowerPAD™ package used by the TPS3705-50DGN?

The MSOP-PowerPAD™ package of the TPS3705-50DGN delivers a junction-to-ambient thermal resistance (R_θJA) of 66.1°C/W - significantly lower than the 118.2°C/W of the SOIC-8 variant (TPS3705-50D). This 44% improvement enables higher power density and sustained operation in thermally constrained spaces, such as sealed industrial enclosures or stacked PCB assemblies. The exposed thermal pad must be soldered to a PCB copper plane for full benefit.