Texas Instruments LP38693SDX-3.3

Overview

LP38693SDX-3.3 from Texas Instruments is a 500-mA, 3.3-V fixed-output CMOS low-dropout linear regulator in WSON-6 package with enable (EN) pin, 250 mV dropout at 500 mA (V_OUT = 5 V), ±2% output accuracy over –40°C to 125°C, and stable operation with 1-µF ceramic output capacitor. It serves as a primary power supply for microcontroller core rails in portable instrumentation.

For engineers reviewing the LP38693SDX-3.3 datasheet, LP38693SDX-3.3 pinout, LP38693SDX-3.3 application, or LP38693SDX-3.3 equivalent, key selection criteria include dropout voltage at full load, EN pin logic thresholds, thermal performance in compact PCB layouts, and compatibility with low-ESR ceramic capacitors without external compensation.

Technical Context

The LP38693SDX-3.3 uses a PMOS pass transistor enabling ground pin current ≤55 µA across full load and temperature range, eliminating base-drive losses. Its trimmed bandgap reference and internal feedback divider set nominal V_OUT = 3.3 V with no external resistors.

It integrates foldback current limiting (350 mA at VIN–VOUT > 5 V; 850 mA at VIN–VOUT < 4 V), thermal shutdown activation at 160°C with 10°C hysteresis, and 1-µA off-state quiescent current when EN is low - all implemented without external components.

Key Specifications

Pinout & Package

LP38693SDX-3.3 is housed in a 3.0 mm × 3.0 mm WSON-6 package with exposed thermal pad (DAP) on bottom for enhanced heat dissipation. The DAP must be soldered to a PCB copper plane per TI AN-1187.

Key Features

Applications

Equivalent & Alternatives

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

Compared with TPL7407LPGQ and TPS7A2033PDBVR, LP38693SDX-3.3 uniquely combines 500-mA output, EN control, SNS capability, and WSON thermal performance - making it the only option among the three qualified for high-current, precision-sense, thermally demanding portable instrumentation.

Availability

LP38693SDX-3.3 is available at Aetrix Electronics and suitable for hard disk drives, notebook computers, battery-powered devices, and portable instrumentation requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for LP38693SDX-3.3 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 designing analog ICs, embedded processors, and digital signal processors for industrial, automotive, and consumer applications.

The LP38693SDX-3.3 belongs to TI's LP3869x family of CMOS LDOs engineered for portable, battery-powered digital systems requiring fast start-up, ultra-low ground current, and ceramic-capacitor stability - targeting space- and power-constrained applications like medical sensors and test equipment.

FAQ

What is the minimum input voltage required for LP38693SDX-3.3 to regulate 3.3 V output?

The LP38693SDX-3.3 requires VIN ≥ (VOUT + VDO). At 500 mA and 25°C, VDO = 250 mV (typical), so minimum VIN = 3.55 V. However, per datasheet Section 7.4, the absolute minimum VIN for functionality is 2.7 V - but regulation only begins once VIN exceeds VOUT + VDO, which rises to 550 mV at 125°C. Therefore, for guaranteed 3.3-V regulation at full load and high temperature, VIN must be ≥3.85 V.

Can LP38693SDX-3.3 operate without the SNS pin connected?

Yes - the SNS pin is optional and WSON-package specific. When unused, SNS must be connected directly to OUT per datasheet Figure 25. Leaving SNS floating is not permitted and may cause regulation instability. The LP38693SDX-3.3 delivers full 3.3-V accuracy at the device pins without SNS; remote sensing is only needed to correct for PCB trace voltage drop between the regulator and load.

What is the maximum allowable power dissipation for LP38693SDX-3.3 in a standard 2-layer PCB layout?

Using R_θJA = 50.6°C/W (WSON-6, High-K board, Table 7.5) and TJ-MAX = 125°C, maximum power dissipation at TA = 70°C is PD-MAX = (125 − 70) / 50.6 ≈ 1.09 W. With VIN = 5 V and VOUT = 3.3 V, this supports up to ~630 mA continuous load. For reliable 500-mA operation at 85°C ambient, thermal design must reduce effective R_θJA via DAP soldering to ≥1-in² copper area.

Does LP38693SDX-3.3 require an input capacitor, and what value is recommended?

Yes - a minimum 1-µF ceramic capacitor is required between IN and GND for stability, per datasheet Section 9.2.2.3. TI recommends placing it within 1 cm of the IN pin and connecting to a clean analog ground. Larger values (e.g., 10 µF) improve high-frequency PSRR and transient response but are not mandatory. Tantalum or film capacitors are acceptable alternatives if ceramic is unavailable.

How does the foldback current limit behave during repeated enable cycles of LP38693SDX-3.3?

Per datasheet Section 8.3.3 CAUTION, foldback current limiting is functional only on the first EN high transition after VIN application. Subsequent toggles of EN do not re-enable foldback - meaning short-circuit current may reach 850 mA (not 350 mA) if VIN–VOUT < 4 V. To ensure consistent protection, avoid repeated EN cycling; instead, use a hardware reset or power-cycle VIN to restore full foldback behavior in fault recovery sequences.