Texas Instruments TPS78618KTTR

Overview

TPS78618KTTR from Texas Instruments is a fixed-output 1.8-V, 1.5-A low-dropout linear regulator with enable input, ultralow noise (48 µV_RMS at 100 Hz–100 kHz), 49 dB PSRR at 10 kHz, and 390 mV dropout at full load. It operates from 2.7 V to 5.5 V input and targets RF power supply rails for VCOs and receivers where spectral purity and transient response are critical.

For engineers reviewing the TPS78618KTTR datasheet, TPS78618KTTR pinout, TPS78618KTTR application, or TPS78618KTTR equivalent, key selection criteria include verified 1.5-A continuous output capability, TO-263-5 package thermal performance (R_θJA = 40.7°C/W), noise-reduction (NR) pin compatibility with 0.1-µF ceramic bypass capacitors, and confirmed fast start-up time of 50 µs with 0.001-µF NR capacitor.

Technical Context

The TPS78618KTTR uses a PMOS pass transistor architecture enabling low dropout and reverse-current protection via an integrated back diode. Its internal 1.225-V bandgap reference feeds a precision error amplifier that regulates output voltage with ±2% accuracy across –40°C to +125°C junction temperature.

Stability is ensured with ≥1-µF ceramic output capacitance and optional NR pin filtering; the 250-kΩ internal resistor on NR forms a low-pass filter with external bypass capacitors to suppress reference noise. Enable logic thresholds (1.7 V high, 0.7 V low) support direct interfacing with 1.8-V/3.3-V microcontrollers.

Key Specifications

Pinout & Package

TPS78618KTTR is housed in a TO-263-5 (KTT) thermally enhanced package with 10.16 mm × 8.42 mm body size and exposed thermal pad electrically connected to GND. The tab must be soldered to a PCB ground plane with a 5×4 thermal via array for optimal R_θJC(bot) = 2.1°C/W performance.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar low-noise, high-PSRR LDO regulator applications.

Compared with TPS79618KTTT and LP5907MFX-1.8/NOPB, the TPS78618KTTR uniquely balances 1.5-A output capability with RF-grade noise and PSRR-making it irreplaceable for high-current, noise-sensitive RF subsystems where neither lower-current alternatives nor higher-current noisier regulators meet all three requirements simultaneously.

Availability

TPS78618KTTR is available at Aetrix Electronics and suitable for RF transceiver modules, portable medical diagnostics, and industrial wireless sensor networks requiring stable component supply across multi-year production cycles.

Supply support for TPS78618KTTR 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 ICs and high-reliability signal chain solutions.

The TPS786 family was engineered specifically for noise-sensitive RF and precision analog applications, delivering ultralow noise, high PSRR, and fast transient response in thermally robust packages for portable and infrastructure equipment.

FAQ

What is the minimum input voltage required for TPS78618KTTR to maintain regulation at full 1.5-A load?

The TPS78618KTTR requires a minimum input voltage of 2.19 V to sustain 1.8-V output regulation at 1.5-A load, calculated from its 390-mV dropout specification (1.8 V + 0.39 V). This allows operation from partially discharged single-cell Li-ion batteries down to 2.2 V while maintaining full output current capability. The device's UVLO threshold of 2.25 V ensures reliable startup above this minimum.

How does the NR pin on TPS78618KTTR reduce output noise, and what capacitor value is recommended?

The NR pin on TPS78618KTTR connects internally to the voltage reference through a 250-kΩ resistor, forming an RC low-pass filter with an external capacitor to suppress reference noise. A 0.1-µF ceramic capacitor yields 48 µV_RMS output noise (100 Hz–100 kHz); values from 0.001 µF to 0.1 µF are supported, with smaller capacitors enabling faster start-up (50 µs) and larger ones reducing noise further at the cost of slower turn-on.

Can TPS78618KTTR safely handle reverse current flow from output to input during power-down sequences?

Yes, the TPS78618KTTR incorporates a PMOS pass transistor with an integrated back diode that conducts reverse current when VIN falls below VOUT (e.g., during hot-swap or input brownout). While this protects internal circuitry, reverse current is not internally limited - external current limiting may be required if sustained reverse conduction exceeds safe board-level limits or causes upstream supply instability.

What thermal derating applies to TPS78618KTTR in a standard 4-layer PCB with 2-oz copper and 5×4 thermal vias under 1.5-A load?

With a 5×4 thermal via array connecting the TO-263-5 exposed pad to inner ground planes, the TPS78618KTTR achieves R_θJC(bot) = 2.1°C/W and R_θJA = 40.7°C/W. At 1.5-A load with 3.3-V input, power dissipation is (3.3 V − 1.8 V) × 1.5 A = 2.25 W; junction temperature rise is 2.25 W × 40.7°C/W = 91.6°C above ambient. For 85°C max ambient, T_J = 176.6°C - exceeding 150°C absolute maximum, so derating to ≤1.1 A or enhanced cooling is required for continuous operation.

Is TPS78618KTTR compatible with ceramic output capacitors smaller than 1 µF, and what are the stability implications?

No - the TPS78618KTTR requires a minimum 1-µF ceramic output capacitor for guaranteed stability across all operating conditions. Using smaller capacitors risks control-loop oscillation, evidenced by output voltage ringing or thermal shutdown during load transients. The datasheet explicitly states "stable with a 1-µF ceramic capacitor" and provides stability regions in Figure 20 confirming instability below 1 µF for typical ESR ranges.