Texas Instruments TPS78618DCQR

Overview

TPS78618DCQR 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), high PSRR (49 dB at 10 kHz), and fast start-up (50 µs). It delivers stable power to noise-sensitive RF analog circuitry in portable wireless systems.

For engineers reviewing the TPS78618DCQR datasheet, TPS78618DCQR pinout, TPS78618DCQR application, or TPS78618DCQR equivalent, key selection criteria include dropout voltage at full load (≤580 mV), thermal performance in SOT-223-6 package (R_θJA = 54.2°C/W), noise-reduction capacitor compatibility (0.001–0.1 µF on NR pin), and shutdown current (<1 µA).

Technical Context

The TPS78618DCQR 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 against line, load, and temperature variations.

Operation includes active enable control (EN logic-high ≥1.7 V), UVLO (2.25–2.65 V), thermal shutdown (~165°C), and foldback current limiting (~2.8 A). The NR pin connects internally to the reference through a 250-kΩ resistor, forming an RC filter with external bypass capacitance to suppress reference noise.

Key Specifications

Pinout & Package

The TPS78618DCQR is housed in a 6-pin SOT-223 (DCQ) package with exposed thermal pad (body size 6.50 mm × 3.50 mm); the tab is electrically connected to GND and must be soldered to PCB ground plane for thermal integrity.

Key Features

Applications

Equivalent & Alternatives

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

Compared with TPS79618DCQ and LP5907MFX-1.8/NOPB, the TPS78618DCQR uniquely balances 1.5-A output, 48-µV_RMS noise, and 49-dB PSRR in a thermally robust SOT-223 package-making it optimal for mid-power RF/analog systems requiring both headroom and spectral purity.

Availability

TPS78618DCQR is available at Aetrix Electronics and suitable for RF front-end modules, portable medical sensors, high-fidelity audio subsystems, and industrial IoT edge nodes requiring stable component supply across extended temperature ranges and multi-year production cycles.

Supply support for TPS78618DCQR 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, embedded processing, and power management ICs for industrial, automotive, and communications markets.

The TPS786 family was engineered for noise-sensitive RF and precision analog applications-delivering ultralow noise, high PSRR, and fast transient response in compact surface-mount packages.

FAQ

What is the minimum input voltage required for TPS78618DCQR to regulate 1.8 V at 1.5 A?

The TPS78618DCQR 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. With VIN ≥ 2.7 V, the device operates within recommended conditions across its full temperature range (–40°C to +125°C). Below 2.7 V, operation is outside specification and may result in unregulated output or thermal stress.

Can TPS78618DCQR operate without the NR (noise-reduction) capacitor?

Yes, the TPS78618DCQR functions without an NR capacitor, but output noise increases significantly-e.g., from 48 µV_RMS (with 0.1 µF) to ~50 µV_RMS (with 0.001 µF). The NR pin is optional for basic regulation but essential for meeting ultralow-noise targets in RF or high-precision analog designs. Omitting it does not affect stability or basic functionality.

What is the thermal resistance (R_θJA) of TPS78618DCQR in its SOT-223-6 package?

The TPS78618DCQR in the DCQ (SOT-223-6) package has a junction-to-ambient thermal resistance (R_θJA) of 54.2°C/W under JEDEC-standard PCB conditions (2s2p board, 20% copper coverage). Actual thermal performance improves with larger copper pour and thermal vias under the exposed tab-TI recommends connecting the tab directly to a solid ground plane for reliable 1.5-A operation.

Does TPS78618DCQR support reverse current flow from OUT to IN?

Yes, the TPS78618DCQR incorporates a built-in back diode across its PMOS pass transistor, allowing reverse current conduction when V_IN < V_OUT (e.g., during power-down). This feature prevents latch-up in cascaded supplies but does not limit reverse current-external diodes or MOSFETs may be needed if uncontrolled reverse flow could damage upstream circuitry.

How does the enable (EN) pin behavior affect system power sequencing in TPS78618DCQR?

The EN pin of TPS78618DCQR provides precise control: logic-high ≥1.7 V enables regulation with 50-µs start-up; logic-low ≤0.7 V forces shutdown with <1 µA supply current. This allows tight coordination with microcontroller GPIOs or power supervisors-enabling staggered rail activation, brown-out recovery, and deep-sleep modes without external discrete logic.