Texas Instruments TPS78405KTTRG3

Overview

TPS78405KTTRG3 from Texas Instruments is a 400-mA, 5-V output, high-input-voltage LDO voltage regulator in a TO-263 (KTT) package. It delivers ±2% output accuracy, 15.5 µV RMS noise, and 200 mV typical dropout at 300 mA, supporting industrial power rails requiring stable 5 V from up to 42 V input-e.g., distributed power systems with wide VIN transients.

For engineers reviewing the TPS78405KTTRG3 datasheet, TPS78405KTTRG3 pinout, TPS78405KTTRG3 application, or TPS78405KTTRG3 equivalent, key selection criteria include reset threshold accuracy (4.65 V ±150 mV), programmable delay via external capacitor, reverse-polarity protection, and guaranteed short-circuit immunity up to 1.2 A.

Technical Context

The TPS78405KTTRG3 integrates a bandgap reference, saturation-controlled series pass transistor, and dedicated reset generator with dual timing thresholds (VDU = 1.8 V typ, VDRL = 0.4 V typ). Its internal protection includes thermal shutdown triggered at 150°C junction temperature and reverse-polarity blocking that prevents current flow when IN is negative relative to GND.

Reset functionality operates independently of load current: VOUT,rt = 4.65 V triggers open-collector RESET assertion with <0.4 V low-level output at 5 mA sink, while delay timing is set by ID,c = 5.5 µA charging CD through the DELAY pin-enabling precise power-on sequencing across temperature (–40°C to 125°C).

Key Specifications

Pinout & Package

TPS78405KTTRG3 uses a 5-pin TO-263 (KTT) thermally enhanced surface-mount package with exposed tab connected internally to GND for improved heat dissipation (θJA = 21.5°C/W).

Key Features

Applications

Equivalent & Alternatives

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

Compared with TPS78405KTTRG3, TPS7B8750QKVURQ1 adds automotive qualification and higher current but removes delay programmability, while MCP1826-5002E/DB offers higher current and lower cost but requires external circuitry to match reset and reverse-protection capabilities.

Availability

TPS78405KTTRG3 is available at Aetrix Electronics and suitable for industrial PLC I/O modules, distributed power supplies, and white goods control boards requiring stable component supply with guaranteed long-term availability and traceable sourcing.

Supply support for TPS78405KTTRG3 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 TPS784xx family targets high-input-voltage LDO applications needing integrated power supervision-designed specifically for industrial systems where wide VIN range, reverse polarity resilience, and deterministic reset behavior are critical.

FAQ

What is the maximum input voltage rating for the TPS78405KTTRG3?

The TPS78405KTTRG3 has an absolute maximum input voltage rating of 45 V, with recommended operating range from 5.5 V to 42 V. Operation beyond 42 V risks exceeding safe power dissipation limits and may trigger thermal shutdown. The device's reverse-polarity protection blocks conduction when IN is negative relative to GND, enabling safe use in battery-powered systems prone to insertion errors. Always verify input transient margins against system-level surge standards such as ISO 7637-2.

Does the TPS78405KTTRG3 require an external capacitor on the DELAY pin to function?

No, the TPS78405KTTRG3 operates as a standard LDO without the DELAY capacitor, but RESET will assert immediately upon undervoltage-without programmable delay. Adding a capacitor (e.g., 47 nF) between DELAY and GND sets the reset delay time (trd ≈ 0.22 × CD × 10⁶ ms); omitting it results in near-instantaneous RESET assertion (<2 µs reaction time). For applications requiring controlled power-up sequencing-such as FPGA configuration or multi-rail SoC initialization-the DELAY capacitor is essential, and its value must be selected per the datasheet's timing curves.

What output capacitor specifications ensure stability for the TPS78405KTTRG3?

The TPS78405KTTRG3 requires a minimum 22 µF output capacitor with ESR ≤5 Ω for guaranteed stability across –40°C to 125°C. Tantalum capacitors meeting these specs are recommended; ceramic capacitors may be used if a small series resistor (typically 0.5–2 Ω) is added to emulate required ESR. Instability manifests as oscillation or excessive output ripple-verified in the "Region of Stability" plots in the datasheet. Larger capacitance (e.g., 47 µF) improves transient response for dynamic loads, but ESR remains the critical parameter for phase margin.

How does reverse-polarity protection work in the TPS78405KTTRG3?

The TPS78405KTTRG3 incorporates internal reverse-polarity protection that prevents current flow from GND to IN when the input voltage is negative relative to ground-effectively acting as a series diode with no forward voltage drop during normal operation. This eliminates the need for an external Schottky diode in battery-powered designs, preserving efficiency and board space. During reverse connection, the device draws negligible current (<1 µA) and presents high impedance, protecting both itself and downstream circuitry. This feature is intrinsic to the IC's architecture and requires no external components or configuration.

Can the TPS78405KTTRG3 drive a 400-mA load continuously at 42-V input?

Yes, the TPS78405KTTRG3 is rated for 400-mA continuous output current, but power dissipation must be validated: at VIN = 42 V and VOUT = 5 V, PD = 400 mA × (42 − 5) V = 14.8 W. With θJA = 21.5°C/W, this yields ΔT = 318°C-far exceeding the 125°C max junction temperature. Successful operation requires substantial heatsinking (e.g., >10 cm² copper pour) or derating-e.g., 150 mA at 42 V input limits PD to ~5.6 W. Always calculate actual junction temperature using measured ambient, PCB thermal design, and θJA/θJC values from the datasheet's thermal tables.