LT1086CT-3.3 - 1.5A, 3.3V Fixed LDO | Analog Devices | TO-220
N.º de pieza: LT1086CT-3.3 ✓ ActivoLT1086CT-3.3 Descripción general
An LDO (low-dropout) linear regulator is a type of voltage regulator that maintains a stable output voltage even when the input supply voltage is only slightly higher than the output - typically 1.05 V to 1.5 V of dropout. LDOs sit within the broader category of linear regulators, which in turn are a subset of voltage regulators and ultimately of power management integrated circuits (PMICs). Unlike switching regulators, an LDO adds no switching noise to the output but dissipates the voltage difference (VIN - VOUT) x IOUT as heat.
Key features of the LT1086CT-3.3 include a 1.5 A maximum output current, fixed 3.3 V output (±1% or ±2% accuracy depending on grade), line/load regulation typically 0.05%, and ripple rejection exceeding 75 dB even at full 1.5 A load. The composite NPN output stage and floating architecture allow all quiescent current to flow to the load, increasing efficiency. The device is pin-compatible with older 3-terminal adjustable regulators such as the LM317 and LM350, simplifying retrofit designs.
Internally, the LT1086 uses a bandgap reference, an error amplifier, and a composite NPN pass element. All quiescent current flows to the load, which boosts efficiency at heavy loads. The reference is trimmed at the wafer stage, so no external adjustment resistor network is required for the fixed-voltage suffix devices - reducing external component count.
Typical applications for the LT1086CT-3.3 include powering 3.3 V logic rails from a 5 V bus, post-regulation after a switching converter (to remove switching ripple), battery-powered systems, and industrial 24 V → 3.3 V conversion where a 5-10 V headroom is acceptable. It is also widely used as a 3.3 V auxiliary supply for microcontroller and DSP subsystems.
When designing with this part, ensure the input-to-output differential stays within the absolute maximum rating and provide at least a 10 µF output capacitor for stability. A small heatsink is recommended when (VIN - VOUT) x IOUT exceeds 2-3 W because the TO-220 thermal resistance typically limits dissipation to 15-20 W without airflow.
This page synthesizes distributor pricing, drop-in alternatives, and practical design notes not found in the manufacturer datasheet.
Alternativas directas para LT1086CT-3.3 — mismo encapsulado, compatible pin a pin. Se excluyen las piezas de otro encapsulado que requieren retrabajo de la PCB.
LT1086CT-5.0
✅ Sustitución directa📋 Alternativa de referencia (no en el catálogo)
LT1086CT-12
✅ Sustitución directa📋 Alternativa de referencia (no en el catálogo)
LT1086CT-2.85
✅ Sustitución directa📋 Alternativa de referencia (no en el catálogo)
LT1086CT-3.6
✅ Sustitución directa📋 Alternativa de referencia (no en el catálogo)
LM1086-3.3
✅ Sustitución directa📋 Alternativa de referencia (no en el catálogo)
MIC29302-3.3
✅ Sustitución directa📋 Alternativa de referencia (no en el catálogo)
LT1086CT-3.3 Valores máximos y características eléctricas
| Tipo de salida | Fixed Positive |
| Output Voltage (Nominal) | 3.3 V |
| Corriente de salida máxima | 1.5 A |
| Tensión de dropout | 1.3 V typical at 1.5 A (per LT1086 family) |
| Line Regulation | 0.05% typical (per LT1086 family) |
| Load Regulation | 0.1% typical (per LT1086 family) |
| Ripple Rejection (PSRR) | >75 dB at 1.5 A (per LT1086 family) |
| Rango de temperatura de funcionamiento | 0C to +125C (commercial) |
| Encapsulado | TO-220-3 (3-lead, through-hole) |
| Tipo de montaje | Through-hole |
| Architecture | NPN composite pass, floating |
| Estado RoHS | Compliant (with #PBF suffix) |
| Pin Compatibility | LM317 / LM350 family (3-terminal) |
Configuración de pines de LT1086CT-3.3
| Pin 1 | GND/ADJ — Ground (internally tied to GND on fixed version; external reference on adjustable version) |
| Pin 2 | VOUT — Regulated output (3.3 V); also electrically connected to metal tab |
| Pin 3 | VIN — Input supply voltage |
Aplicaciones típicas
LT1086CT-3.3 es adecuado para 6 aplicacións: 3.3V Logic Rail Power Supply, Post-Regulation After Switching Converter, Industrial 24V to 3.3V Conversion, Battery-Powered System 3.3V Rail, Microcontroller Auxiliary Supply, Test and Measurement Bench Power.
3.3V Logic Rail Power Supply
The LT1086CT-3.3's fixed 3.3 V output and 1.5 A current capability make it an ideal linear post-regulator for powering 3.3 V CMOS logic, microcontrollers, and low-voltage digital ICs. According to the Analog Devices datasheet, the device delivers up to 1.5 A continuously with typical load regulation of 0.1% - sufficient for most MCU subsystems. A typical circuit places the LT1086CT-3.3 between a 5 V switching pre-regulator and the 3.3 V logic rail, with 10 µF input/output tantalum capacitors for stability. The regulator eliminates high-frequency switching noise that would otherwise couple into sensitive digital I/O. Compared to a direct buck converter solution, the LT1086CT-3.3 costs less, requires no inductors, and adds zero EMI - trading efficiency for simplicity.
Recomendado
Post-Regulation After Switching Converter
The LT1086CT-3.3 is frequently used as a post-regulator (linear regulator) downstream of a switching converter to remove ripple and noise from a pre-regulated rail. According to the LT1086 datasheet, ripple rejection exceeds 75 dB at full load - sufficient to attenuate switching frequencies (typically 100 kHz-1 MHz) by a factor of ~5600. A common topology uses a 12 V → 5 V switching converter followed by an LT1086CT-3.3 to produce a clean 3.3 V rail. Compared to adding output LC filters on the switching converter, the LDO approach provides better low-frequency PSRR and a smaller board footprint, at the cost of (5 V - 3.3 V) × 1.5 A = 2.55 W of dissipation that requires a small heatsink.
Recomendado
Industrial 24V to 3.3V Conversion
In industrial automation systems powered from a 24 V bus, the LT1086CT-3.3 provides a simple, low-cost means to derive a 3.3 V logic rail. With a maximum input voltage tolerance and 1.5 A output, the LT1086CT-3.3 can deliver 3.3 V directly from a 24 V supply, dissipating (24 V - 3.3 V) × 1.5 A = 31 W at full load - which requires substantial heatsinking. A more practical approach combines a switching pre-regulator (e.g., 24 V → 5 V) followed by the LT1086CT-3.3 to keep dissipation below 2.5 W. According to the Analog Devices datasheet, the device operates from 0C to 125C junction temperature, suitable for enclosed industrial cabinets.
Recomendado
Battery-Powered System 3.3V Rail
The LT1086CT-3.3's low dropout of approximately 1.3 V at 1.5 A allows it to maintain a regulated 3.3 V output from battery sources as they discharge. According to the LT1086 family datasheet, when fed from a 4-cell NiMH or Li-ion battery (4.0 V fully charged, 3.6 V nominal, 3.0 V discharged), the LDO maintains regulation until VIN drops to approximately 4.6 V. While not as efficient as a buck converter for battery applications, the LT1086CT-3.3's simplicity, lack of switching noise, and instant-on behavior make it suitable for instrumentation, sensor nodes, and low-power embedded systems where simplicity outweighs efficiency concerns.
Recomendado
Microcontroller Auxiliary Supply
Many microcontroller subsystems require a stable 3.3 V rail separate from the main digital supply. The LT1086CT-3.3 provides a low-noise, 1.5 A linear regulator suitable for powering an MCU's analog or RTC domain. According to the Analog Devices datasheet, line/load regulation of 0.05%/0.1% is sufficient for most MCU ADC reference requirements. The fixed 3.3 V output eliminates external resistor dividers and the associated accuracy loss. Compared to using the main switching converter directly, the LT1086CT-3.3 isolates analog circuits from switching noise, improving ADC SNR and reducing jitter on RTC oscillators.
Recomendado
Test and Measurement Bench Power
The LT1086CT-3.3 is commonly used in laboratory bench power supplies as a 3.3 V fixed rail for prototyping 3.3 V logic circuits, microcontrollers, and embedded systems. With its TO-220-3 package, the LT1086CT-3.3 can be heatsinked directly to a chassis or aluminum plate for continuous 1.5 A operation. According to the datasheet, ripple rejection of 75 dB produces a clean DC rail suitable for powering noise-sensitive analog prototyping. The 3-terminal pinout allows easy breadboard mounting with TO-220 sockets, and the fixed voltage eliminates adjustment trimpots.
Recomendado
Resumen de productos recomendados
Datos de referencia de ingeniería para LT1086CT-3.3 — comparación, orientación de diseño e información de cumplimiento.
Guía de selección
Comparación con alternativas
| Parámetro | Este producto | LT1086CT-5.0 | LT1086CT-3.6 | LT1086CT-12 | LM1086-3.3 | MIC29302-3.3 |
|---|---|---|---|---|---|---|
| Package | TO-220-3 | TO-220-3 - same | TO-220-3 - same | TO-220-3 - same | TO-220-3 - same | TO-220-3 - same |
| Brand | Analog Devices | Analog Devices | Analog Devices | Analog Devices | Texas Instruments | Microchip Technology |
| Output Voltage | 3.3 V | 5.0 V | 3.6 V | 12 V | 3.3 V | 3.3 V |
| Maximum Output Current | 1.5 A | 1.5 A | 1.5 A | 1.5 A | 1.5 A | 3.0 A |
| Pinout Compatibility | LM317 family | LM317 family - same | LM317 family - same | LM317 family - same | ||
| Min Output Capacitor | 10 µF | 10 µF | 10 µF | 10 µF |
Diferenciadores clave
- Drop-in 3-terminal pinout to LM317 family (frente a LM317 (adjustable))
- Higher output current than LM1086-3.3 alternative (frente a MIC29302-3.3 (Microchip))
- Multiple fixed-voltage siblings for design flexibility (frente a LM1086-3.3)
Notas de diseño
Estimated: At VIN=5 V, VOUT=3.3 V, IOUT=1.5 A, the LT1086CT-3.3 dissipates (5-3.3) × 1.5 = 2.55 W. The TO-220 package has a typical θJA of 50 °C/W without a heatsink, giving a 128 °C junction rise above ambient - exceeding the 125 °C maximum. A small clip-on heatsink (θSA ~20 °C/W) or 100 cm² of copper PCB area is required for reliable full-load operation above 2 W dissipation.
The LT1086CT-3.3 requires a minimum 10 µF output capacitor for stability per the Analog Devices datasheet. Use low-ESR tantalum or aluminum electrolytic capacitors - ceramic capacitors with very low ESR may cause instability. Place input and output capacitors within 1-2 cm of the device pins to minimize parasitic inductance. A 1 µF ceramic bypass on VIN in parallel with the bulk capacitor improves high-frequency PSRR.
Do not use ceramic-only output capacitors below 10 µF - the LT1086 family requires the ESR of tantalum or aluminum electrolytic for loop compensation. Do not exceed the absolute maximum input-to-output differential - check the datasheet for the rating (typically 25-30 V). The metal tab of the TO-220 package is electrically connected to VOUT; provide adequate clearance if VOUT differs from chassis ground to avoid shorts.
Mount the LT1086CT-3.3 vertically with the metal tab facing upward for natural convection cooling. Provide at least 100 cm² of copper pour on the PCB connected to the tab for heatsinking. If higher power dissipation is expected (>5 W), use a clip-on or bolt-on heatsink with thermal compound. Route the GND pin (Pin 1) trace away from noisy switching nodes to avoid injecting switching noise into the regulation loop.
Información de cumplimiento
RoHS and REACH compliant per the #PBF suffix designation. Not AEC-Q100 qualified - this is a commercial/industrial grade part. Lead-free termination per JEDEC J-STD-020. Halogen-free status not explicitly stated in available data.
