Texas Instruments TPS3705-50DRG4

Overview

TPS3705-50DRG4 from Texas Instruments is a precision 5-V supply voltage supervisor IC with integrated watchdog timer, power-fail comparator, and 200-ms fixed reset delay. It monitors VDD ≥ 4.45 V (VIT–), asserts active-low RESET during brownout or power-up, and provides WDO/WDI watchdog functionality for microcontroller-based systems in industrial and automotive applications.

For engineers reviewing the TPS3705-50DRG4 datasheet, TPS3705-50DRG4 pinout, TPS3705-50DRG4 application, or TPS3705-50DRG4 equivalent, key selection criteria include its 4.55-V threshold accuracy, 50 µA max supply current, −40°C to 85°C operation, SOIC-8 package, and watchdog timeout of 1.6 s - all critical for reliable system initialization and fault recovery.

Technical Context

The TPS3705-50DRG4 implements dual supervision: a precision bandgap-referenced VDD monitor with 70-mV hysteresis and a separate PFI/PFO comparator for auxiliary rail monitoring (e.g., 12 V via resistor divider). Its internal oscillator drives a watchdog timer that times out after 1.6 s if WDI transitions are missed.

RESET assertion occurs at VDD < 4.45 V (VIT–) with 3-µs propagation delay; manual reset is triggered by low pulse on MR. The device operates from 2 V to 6 V, requires no external capacitor for reset timing, and features 5-pF input capacitance and ±1 µA PFI input leakage.

Key Specifications

Pinout & Package

TPS3705-50DRG4 is packaged in an 8-pin SOIC (D package), body size 3.90 mm × 4.90 mm, with exposed pad not electrically connected. Pin functions are validated per TI SLVS184F datasheet Figure 6-1 and Table 6.1.

Key Features

Applications

Equivalent & Alternatives

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

Compared with TPS3705-50D and MAX706CSA+, the TPS3705-50DRG4 uniquely combines 5-V precision supervision, integrated watchdog, and industry-standard SOIC-8 packaging - delivering full system-level reliability without adding discrete timers or secondary supervisors.

Availability

TPS3705-50DRG4 is available at Aetrix Electronics and suitable for industrial automation, automotive electronics, and portable medical devices requiring stable component supply, long-term lifecycle support, and guaranteed traceability.

Supply support for TPS3705-50DRG4 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 specializing in analog and embedded processing technologies, with leadership in power management, signal chain, and microcontrollers.

The TPS370x family was designed specifically for robust power-supply supervision in DSP, MCU, and MPU systems - emphasizing precision thresholds, low quiescent current, and integrated watchdog functionality for mission-critical restart behavior.

FAQ

What is the exact reset threshold voltage for TPS3705-50DRG4?

The TPS3705-50DRG4 has a guaranteed negative-going input threshold voltage (VIT–) of 4.45 V (min), 4.55 V (typ), and 4.65 V (max) over −40°C to +85°C. This 5-V nominal threshold ensures reliable detection of 5-V rail collapse before downstream logic fails, with 70-mV hysteresis preventing chatter during marginal conditions. The value is factory-trimmed and does not require external calibration.

Does TPS3705-50DRG4 require an external capacitor for reset timing?

No, the TPS3705-50DRG4 uses an internal oscillator and logic to generate a precise 200-ms reset delay - no external capacitor is needed. This eliminates timing drift due to capacitor tolerance/aging and reduces PCB area and BOM count. The delay is fixed and specified across temperature and supply voltage (2 V to 6 V), ensuring consistent boot behavior in all operating conditions.

How does the watchdog function work on TPS3705-50DRG4?

The TPS3705-50DRG4 watchdog timer times out after 1.1–2.3 s (typ 1.6 s) if no edge (rising or falling) is detected on the WDI pin. Each valid transition resets the timer. If timeout occurs, WDO asserts low and remains low until cleared by VDD cycling or MR pulse. Leaving WDI unconnected disables the watchdog. This provides autonomous firmware hang detection independent of the host MCU's clock or software state.

Can TPS3705-50DRG4 monitor a 12-V rail in addition to its 5-V supply?

Yes, the TPS3705-50DRG4 uses its PFI (Power-Fail Input) pin to monitor auxiliary rails. For a 12-V rail, a resistor divider (e.g., 910 kΩ + 120 kΩ) scales the voltage to ~1.25 V - within the PFI threshold range of 1.20–1.30 V. When scaled voltage drops below threshold, PFO asserts low. This dual-rail capability enables single-chip supervision of both main and backup supplies without external comparators.

What is the maximum supply voltage rating for TPS3705-50DRG4?

The absolute maximum supply voltage (VDD) for TPS3705-50DRG4 is 7 V, but continuous operation above 6 V is not recommended. The device is characterized for reliable operation from 2 V to 6 V per Recommended Operating Conditions. Exceeding 6 V may cause parametric shift or accelerated aging; TI specifies "not more than t = 1000 h continuously" at 7 V. Designers should maintain VDD ≤ 6 V for full specification compliance.