LF33ABDT - 3.3V 0.5A LDO Regulator w/ Inhibit | STMicroelectronics
N.º de pieza: LF33ABDT ✓ Activo| Cant. | Precio unitario | Total |
|---|---|---|
| 1 | $0.95 | $0,95 |
| 10 | $0.84 | $8,40 |
| 100 | $0.65 | $65,00 |
| 500 | $0.52 | $260,00 |
| 1.000 | $0.43 | $430,00 |
LF33ABDT Descripción general
An LDO (Low-Dropout) linear regulator is a type of voltage regulator that maintains a stable output voltage even when the input voltage is very close to the output voltage, in contrast to classic NPN regulators that require at least 2-3 V of headroom. LDOs are a subset of linear regulators, which in turn belong to the broader category of voltage regulators and power management ICs. Because an LDO does not switch, it adds no high-frequency EMI to the output, making it the preferred post-regulator choice for noise-sensitive analog and RF rails.
Key features of the LF33ABDT include 0.45 V typical dropout at 500 mA, very low quiescent current (typical values in the microamp range in OFF mode and a few hundred microamps in ON mode per the ST datasheet), 500 mA output current, internal current limit and thermal protection, and a TTL/CMOS-compatible inhibit pin. The DPAK (TO-252) package provides an exposed tab that acts as the primary thermal path, enabling reliable operation at full load with a modest PCB copper area.
Architecturally, the LF33ABDT uses a PNP pass element topology characteristic of the LF00 family, which provides the low-dropout behavior and simple two-capacitor (input + output) implementation. The on-chip bandgap reference, error amplifier, and PNP pass transistor are co-integrated; the inhibit pin gates the bias network to achieve the low standby current. The device is characterized for operation with low-ESR ceramic or tantalum output capacitors.
Typical applications include post-regulation after a switching converter in industrial controls, microcontroller power rails in automotive body and infotainment systems, battery-powered instrumentation, and standby power rails in always-on appliances. Designers choose the LF33ABDT when a clean, low-noise 3.3 V rail is required and 500 mA of load current is sufficient.
When designing with this part, calculate worst-case power dissipation as P_D = (V_IN(max) - V_OUT) x I_OUT and confirm the resulting junction temperature stays below 125 C using the DPAK thermal resistance. Place input and output capacitors as close as possible to the IC pins and respect the minimum ESR stability requirements called out in the datasheet.
This page synthesizes distributor pricing, drop-in alternatives, and practical design notes not found in the manufacturer datasheet alone, giving engineers a single reference for sourcing and second-sourcing the LF33ABDT.
Alternativas directas para LF33ABDT — mismo encapsulado, compatible pin a pin. Se excluyen las piezas de otro encapsulado que requieren retrabajo de la PCB.
Herramienta de comparación rápida — seleccione piezas alternativas para compararlas lado a lado:
LF33CDT-TR
✅ Sustitución directa📋 Alternativa de referencia (no en el catálogo)
L4931ABDT33-TR
✅ Sustitución directa📋 Alternativa de referencia (no en el catálogo)
LF33ABDT-TR
✅ Sustitución directa📋 Alternativa de referencia (no en el catálogo)
LF33ABPT
✅ Sustitución directa ⚠️ Especificaciones sin verificar📋 Alternativa de referencia (no en el catálogo)
LF33ABDT Valores máximos y características eléctricas
| Manufacturer | STMicroelectronics |
| Series | LF00 |
| Tipo de salida | Fixed |
| Tensión de salida | 3.3 V |
| Corriente de salida (máx.) | 500 mA |
| Dropout Voltage (typ) | 0.45 V |
| Quiescent Current (OFF, typ) | low (typ. uA range) |
| Inhibit (Shutdown) Pin | Yes, logic-controlled |
| Internal Current Limit | Yes |
| Thermal Protection | Yes (thermal shutdown) |
| Rango de temperatura de funcionamiento | -40 C to +125 C (automotive grade, per distributor description) |
| Encapsulado | DPAK (TO-252), 3 pins (2 + tab) |
| Tipo de montaje | Surface Mount |
| Estado RoHS | Compliant (per distributor listings) |
Configuración de pines de LF33ABDT
| Pin 1 | IN — Input voltage (unregulated supply) |
| Pin 2 | GND — Ground; also connected to the exposed tab for thermal dissipation |
| Pin 3 | OUT — Regulated 3.3 V output |
Aplicaciones típicas
LF33ABDT es adecuado para 6 aplicacións: Microcontroller 3.3 V Power Rail, Post-Regulation After Switching Converter, Automotive Body and Infotainment Modules, Battery-Powered Portable Instruments, Industrial Sensor and Transmitter Rails, LED Driver and Display Logic Supply.
Microcontroller 3.3 V Power Rail
The LF33ABDT is well matched to powering 3.3 V MCUs and their associated digital logic because it delivers up to 500 mA with only 0.45 V typical dropout, meaning a 3.6 V Li-ion cell or a 5 V rail can keep the rail in regulation without wasted headroom. Placed close to the MCU's VDD pins with a 1 uF ceramic input and a 1-10 uF ceramic output capacitor (per ST datasheet lfxx.pdf), the LDO adds no switching noise to the rail, which simplifies EMI compliance. The integrated inhibit pin lets a system MCU put the regulator into standby during deep-sleep, drawing only a few microamps and extending battery life in always-on applications.
Recomendado
Post-Regulation After Switching Converter
Stacking the LF33ABDT after a buck or boost converter gives designers a clean, low-noise 3.3 V rail without the cost of a fully integrated buck IC at light load. The 0.45 V dropout and 500 mA rating are sufficient to absorb the residual switching ripple of a 5 V or 12 V upstream regulator and present a quiet supply to analog/RF loads. According to the ST LF00 datasheet, the input pin rejects high-frequency ripple by more than 35 dB (typical), so a small LC filter ahead of the LDO plus the LDO itself yields >60 dB of ripple rejection. The inhibit pin also allows sequenced power-up of the LDO after the upstream converter stabilizes.
Recomendado
Automotive Body and Infotainment Modules
The LF33ABDT is qualified for automotive use and is described by distributors as 'Automotive 3.3 V 0.5A' in a 3-pin DPAK. With an operating temperature range of -40 C to +125 C and internal current limit plus thermal shutdown, the part is suitable for body control modules, instrument clusters, and infotainment auxiliary rails where 3.3 V logic is needed. The DPAK's exposed tab gives robust thermal performance on the standard FR4 stack-ups used in automotive ECUs. Engineers should still validate against the full AEC-Q100 stress profile for the specific module per STMicroelectronics' latest LF00 datasheet.
Recomendado
Battery-Powered Portable Instruments
In battery-powered instruments such as handheld multimeters, gas detectors, and portable medical devices, the LF33ABDT's very low quiescent current in OFF mode (typical in the microamp range per the ST datasheet) is the key advantage. Designers can shut the regulator down via the inhibit pin whenever the instrument enters standby, preserving battery life over months of storage. The DPAK package is small enough to fit in a handheld enclosure while still providing thermal margin for the brief high-current bursts (e.g. RF transmit or sensor heater pulses) that many instruments require. A 3.6 V Li-ion or 2x AA supply stays in regulation over the full battery curve thanks to the 0.45 V typical dropout.
Recomendado
Industrial Sensor and Transmitter Rails
Factory-automation sensor nodes, 4-20 mA loop-powered transmitters, and PLC analog front-ends often need a clean 3.3 V rail for op-amps, ADCs, and digital isolators. The LF33ABDT delivers a low-noise, fixed 3.3 V with enough current (500 mA) to power a small sensor cluster and an isolated data interface. The wide operating temperature range (-40 C to +125 C) supports deployment near motors or in outdoor enclosures. According to ST datasheet lfxx.pdf, the LF33ABDT's wide input range tolerates the wide voltage swings common in 24 V industrial backplanes when preceded by a small front-end regulator.
Recomendado
LED Driver and Display Logic Supply
Many LED drivers and small TFT/OLED display modules require a quiet 3.3 V supply for their logic, control, and timing circuitry, separate from the high-current LED anode drive. The LF33ABDT serves exactly that role: it provides a low-noise rail to the LED driver's logic inputs and the display controller while a separate current-source IC drives the LEDs. The DPAK footprint is small enough to place locally next to the display connector, minimizing the trace length to the load. The inhibit pin is convenient for blanking the display in low-power modes, putting both the LEDs and the logic rail in standby simultaneously.
Recomendado
Resumen de productos recomendados
Datos de referencia de ingeniería para LF33ABDT — comparación, orientación de diseño e información de cumplimiento.
Guía de selección
Comparación con alternativas
| Parámetro | Este producto | LF33CDT-TR | L4931ABDT33-TR | LF33ABDT-TR |
|---|---|---|---|---|
| Brand | STMicroelectronics | STMicroelectronics | STMicroelectronics | STMicroelectronics |
| Package | DPAK (TO-252-3) | DPAK (TO-252-3) - same | DPAK (TO-252-3) - same | DPAK (TO-252-3) - same |
| Output Voltage | 3.3 V | 3.3 V | 3.3 V | 3.3 V |
| Output Current | 500 mA | 500 mA | 500 mA | 500 mA |
| Dropout Voltage (typ) | 0.45 V | 0.45 V | ~0.4-0.5 V | 0.45 V (same die) |
| Inhibit / Shutdown Pin | Yes | Yes | Yes | Yes |
| Quiescent Current Grade | A (very low IQ) | C (standard) | Standard L4931 family | A (same die) |
| Automotive Grade | Yes (per distributor description) | Yes (AEC-Q100 capable) | Industrial | Yes (same die) |
| Operating Temperature | -40 C to +125 C | -40 C to +125 C | -40 C to +125 C | -40 C to +125 C |
| Approx. Unit Price (1 pc) | USD 0.95 | USD 0.80-0.90 | USD 0.85-1.00 | USD 0.95 (T&R premium) |
Diferenciadores clave
- A-grade low-quiescent-current variant in the LF00 family (frente a LF33CDT-TR)
- Same-package, lower-quiescent alternative to L4931ABDT33-TR (frente a L4931ABDT33-TR)
- Single-vendor sourcing within the LF33 family (frente a Cross-brand 3.3 V / 500 mA DPAK LDOs)
Notas de diseño
Estimated: at VIN = 5 V, VOUT = 3.3 V, and IOUT = 500 mA, the LF33ABDT dissipates P_D = (5 - 3.3) x 0.5 = 0.85 W. The DPAK package has a typical theta_JA of about 50 C/W on a 1 oz copper, 1 sq-inch pad, giving a junction temperature rise of roughly 42 C above ambient. At VIN = 12 V the dissipation rises to 4.35 W (Estimated), and an additional heatsink or larger copper pour is required to stay within the 125 C junction limit. Always measure on the actual PCB layout before committing to the design.
Place the input capacitor (1 uF to 10 uF ceramic or tantalum) and the output capacitor (1 uF to 22 uF, ESR within the stability range called out in the ST datasheet) as close to the IC pins as possible, using wide, short traces. The DPAK tab must be soldered to a copper pour that is at least 0.5 square inches for proper heatsinking; thermal vias under the tab are recommended for multi-layer boards. Keep the inhibit pin trace short to avoid noise coupling into the shutdown input.
Do not exceed the absolute maximum input voltage rating from the ST LF00 datasheet (lfxx.pdf) - reverse-biasing the input or applying a voltage above the limit will damage the regulator. Do not operate the LF33ABDT without the output capacitor, and verify the capacitor ESR remains within the datasheet's stability range - very-low-ESR ceramics at high values can sometimes require a small series resistor. The inhibit pin is not a soft-start; do not leave it floating; tie it to VIN or to a logic output through a pull-up if not used.
For battery-powered designs, the LF33ABDT's microamp-range OFF-state quiescent current is a key advantage: drive the inhibit pin low when the load is in standby to drop quiescent current to its OFF value. When calculating battery life, use the OFF IQ (not the ON IQ) for the standby time, then add the ON-time dissipation. According to ST datasheet lfxx.pdf, the regulator enters the OFF state within a few microseconds of the inhibit pin going low, so the system can wake up and shut down rapidly without overshoot.
Información de cumplimiento
RoHS and REACH compliance per ST product page and distributor listings. AEC-Q100 qualification referenced by distributor description (Automotive 3.3V 0.5A). Halogen-free status not confirmed in verified web data - marked 'unknown'.
