Texas Instruments TPS78618DCQ

Overview

TPS78618DCQ from Texas Instruments is a fixed-output 1.8-V, 1.5-A low-dropout linear regulator with ultralow noise (48 µV_RMS), high PSRR (49 dB at 10 kHz), and fast start-up (50 µs). It uses a PMOS pass element, supports 2.7–5.5 V input, and delivers stable regulation for RF power amplifiers, ADC reference supplies, and precision analog front-ends.

For engineers reviewing the TPS78618DCQ datasheet, TPS78618DCQ pinout, TPS78618DCQ application, or TPS78618DCQ equivalent, key selection criteria include dropout voltage at full load (≤580 mV), noise performance with 0.1 µF NR capacitor, thermal resistance (R_θJA = 54.2 °C/W), and compatibility with 1-µF ceramic output capacitors.

Technical Context

The TPS78618DCQ implements a PMOS-based LDO architecture with internal 1.225-V bandgap reference, UVLO (2.25–2.65 V), and thermal shutdown (~165°C). Its noise-reduction (NR) pin integrates a 250-kΩ internal resistor to form an RC filter with external bypass capacitance, directly lowering reference-induced output spectral noise.

It features active current limiting (~2.8 A), fast line/load transient response, and enable-controlled shutdown reducing quiescent current to <1 µA. The device operates across –40°C to +125°C junction temperature and is stable with ≥1-µF ceramic output capacitance and minimal ESR.

Key Specifications

Pinout & Package

The TPS78618DCQ is housed in a 6-pin SOT-223 package (6.50 mm × 3.50 mm) with exposed thermal pad connected to GND. The tab is electrically grounded and must be soldered to PCB copper for thermal management.

Key Features

Applications

Equivalent & Alternatives

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

Compared with TPS79618DCQ and MCP1826T-1802E/DB, the TPS78618DCQ offers superior RF noise suppression and faster transient recovery-critical for signal integrity in wireless transceivers and high-resolution data acquisition systems.

Availability

TPS78618DCQ is available at Aetrix Electronics and suitable for RF power amplifier biasing, precision ADC reference supplies, and portable audio subsystems requiring stable component supply across production lifecycles.

Supply support for TPS78618DCQ 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 since the 1980s.

The TPS786 family was designed specifically for noise-sensitive analog and RF applications-including VCOs, receivers, and high-speed data converters-where ultralow output noise and high-frequency PSRR are essential.

FAQ

What is the minimum input voltage required for TPS78618DCQ to regulate 1.8 V at 1.5 A?

The TPS78618DCQ requires a minimum input voltage of 2.38 V to maintain regulation at 1.5 A, based on its maximum dropout voltage of 580 mV. At lighter loads, dropout decreases-e.g., 390 mV at 1.5 A for TPS78630-but TPS78618DCQ datasheet specifies ≤580 mV. Always ensure VIN ≥ VOUT + VDO across temperature and process variation. The TPS78618DCQ remains functional down to VIN = 2.7 V per recommended operating conditions.

Can TPS78618DCQ operate with a 1-µF output capacitor, and what type is recommended?

Yes, the TPS78618DCQ is stable with a minimum 1-µF ceramic output capacitor, as confirmed in the datasheet's "Stable With a 1-μF Ceramic Capacitor" feature. X5R or X7R dielectrics are recommended for stable capacitance over temperature and bias. Avoid high-ESR types like aluminum electrolytic or tantalum unless compensated per TI's layout guidelines. The TPS78618DCQ does not require series resistance for stability with ceramic caps.

How does the NR pin function in TPS78618DCQ, and what capacitor value should be used?

The NR pin in TPS78618DCQ 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. For optimal noise reduction, TI specifies 0.1 µF ceramic (low-leakage, X7R) yields 48 µV_RMS output noise. Smaller values (e.g., 0.001 µF) reduce start-up time to 50 µs but increase integrated noise; larger values slow start-up and risk incomplete charging. The TPS78618DCQ NR pin must not be left floating.

Does TPS78618DCQ include thermal shutdown, and at what temperature does it activate?

Yes, the TPS78618DCQ includes thermal shutdown that activates at approximately 165°C junction temperature to prevent permanent damage. Once tripped, the device halts regulation and remains off until the junction cools to ~140°C, at which point normal operation resumes automatically. This behavior is documented in Section 7.3.1 of the datasheet. Thermal performance depends on PCB copper area-R_θJA = 54.2 °C/W assumes JEDEC-standard 2-layer board with defined copper coverage.

Is TPS78618DCQ pin-compatible with other devices in the TPS786 family, such as TPS78633DCQ?

Yes, all TPS786 fixed-output variants-including TPS78618DCQ, TPS78633DCQ, and TPS78650DCQ-share identical 6-pin SOT-223 (DCQ) pinout and package dimensions. Pin functions (EN, IN, GND, OUT, NR, GND) are identical across fixed versions. Output voltage is set internally; no external feedback resistors are needed. This allows direct voltage-scaling substitutions in existing layouts without PCB revision, provided input voltage headroom and thermal limits are re-verified for each VOUT.