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STMicroelectronics LF33CDT
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- Part No.:
- LF33CDT
- Manufacturer:
- STMicroelectronics
- Package:
- TO-252-3, DPAK (2 Leads + Tab), SC-63
- Datasheet:
-
LF33CDT.pdf
- Description:
- IC REG LINEAR 3.3V 500MA DPAK
- Quantity:
- Payment:
- Shipping:
Inventory:2,037
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Product details
Overview
LF33CDT from STMicroelectronics is a 3.3 V, 500 mA very low dropout (LDO) linear voltage regulator in DPAK package with logic-controlled shutdown, ±2% output voltage accuracy at 25°C, 0.4 V typical dropout at 500 mA, and 50 µA quiescent current in OFF mode. It serves as a local power supply for microcontroller cores, sensor interfaces, and low-power IoT peripherals in battery-operated industrial and automotive control modules.
For engineers reviewing the LF33CDT datasheet, LF33CDT pinout, LF33CDT application, or LF33CDT equivalent, key selection considerations include its 0.4 V dropout at full load, 50 µA shutdown current, 80 dB supply rejection at 120 Hz, compatibility with 2.2 µF ceramic output capacitors, and operation across –40°C to 125°C junction temperature.
Technical Context
The LF33CDT implements a PNP pass transistor architecture enabling ultra-low dropout voltage and stable regulation with minimal external components. Its internal current and thermal limiting protect against overload and fault conditions without requiring external sensing circuitry.
Logic-controlled shutdown (TTL-compatible INH pin) enables system-level power sequencing and dynamic power gating. The device maintains regulation down to 4.3 V input at 500 mA load, with line and load regulation specified at ≤16 mV over full operating range.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Output Voltage | 3.3 V ±2% at 25°C - ensures reliable logic-level compliance for 3.3 V digital systems |
| Max Output Current | 500 mA - supports mid-power MCU domains and peripheral rails |
| Dropout Voltage | 0.4 V typ. at 500 mA - enables operation from single-cell Li-ion or 5 V bus with margin |
| Quiescent Current | 50 µA in OFF mode - extends battery life in standby/sleep states |
| Supply Rejection | 80 dB at 120 Hz - suppresses ripple from switching pre-regulators or noisy DC sources |
| Operating Temp | –40°C to +125°C - qualified for under-hood automotive and industrial ambient environments |
| Stability Cap | 2.2 µF ceramic - eliminates need for electrolytic or tantalum, reducing board area and cost |
Pinout & Package
DPAK (TO-252) surface-mount package with exposed thermal pad for enhanced power dissipation; thermally optimized for PCB copper pour mounting.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 (IN) | Input Supply | DC input connection; accepts 4.3–16 V for regulated 3.3 V output |
| 2 (GND) | Ground Reference | Common return path for input, output, and control circuits |
| 3 (OUT) | Regulated Output | Stable 3.3 V supply rail; requires ≥2.2 µF ceramic capacitor to ground |
| 4 (INH) | Shutdown Control | TTL-compatible enable input; <0.8 V disables regulator (50 µA IQ), >2 V enables |
Key Features
| Feature | Design Value |
|---|---|
| Very low dropout | 0.4 V at 500 mA load - sustains regulation with minimal headroom, critical for battery discharge curves |
| Logic-controlled shutdown | Active-high TTL-compatible INH pin - enables precise system-level power state management |
| Low-noise output | 50 µV RMS noise (10 Hz–100 kHz) - suitable for analog sensors and ADC reference supplies |
| Internal protection | Current limit and thermal shutdown - eliminates need for external foldback or thermal sensors |
| Wide input range | 4.3 V to 16 V - compatible with 5 V, 12 V, and automotive battery-supplied systems |
Applications
| Automotive Body Control Module | Industrial Sensor Node |
|---|---|
Use Scenario: Powering CAN transceiver and microcontroller core in door module with 12 V battery input. IC Role / Device Role / Timing Role: Local LDO providing clean, sequenced 3.3 V supply with shutdown synchronized to vehicle sleep mode. Use Value: 50 µA OFF-mode current reduces parasitic drain; 0.4 V dropout ensures regulation down to 9.5 V battery voltage. |
Use Scenario: Regulating power for MEMS accelerometer, BLE SoC, and precision ADC in wireless condition monitor. IC Role / Device Role / Timing Role: Primary 3.3 V rail generator with low noise and fast transient response for mixed-signal integrity. Use Value: 50 µV output noise preserves ADC SNR; 2.2 µF ceramic stability simplifies layout in space-constrained enclosures. |
| Medical Portable Monitor | Smart Energy Meter |
Use Scenario: Supplying display controller and touch interface in handheld vital sign analyzer powered by Li-ion. IC Role / Device Role / Timing Role: Low-quiescent LDO delivering stable 3.3 V during active measurement and deep sleep cycles. Use Value: 50 µA shutdown current extends battery runtime beyond 72 hours in standby; DPAK thermal performance supports sealed enclosure operation. |
Use Scenario: Powering metrology ASIC and real-time clock in DIN-rail mounted electricity meter with 24 V DC input. IC Role / Device Role / Timing Role: Secondary LDO generating isolated 3.3 V rail from intermediate 5 V supply. Use Value: 80 dB PSRR at 120 Hz rejects ripple from upstream buck converter; –40°C to 125°C rating covers extended outdoor temperature range. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar LDO regulator applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LD33CV | Same 3.3 V/500 mA output, but TO-220 package and no shutdown pin | Lacks logic control; suited for fixed-on applications without power sequencing | Select when board space allows through-hole mounting and shutdown is unnecessary |
| TLV73333PDBVR | 3.3 V/300 mA, 50 µA IQ, but only 0.22 V dropout at 300 mA and SOT-23-5 package | Lower current capacity and smaller footprint; no thermal pad for high-temp operation | Prefer for compact, lower-power designs where 125°C operation and 500 mA are not required |
Compared with LD33CV and TLV73333PDBVR, the LF33CDT uniquely balances 500 mA capability, DPAK thermal performance, TTL shutdown control, and automotive-grade temperature range-making it optimal for space-constrained, high-reliability embedded power rails requiring dynamic control.
Availability
LF33CDT is available at Aetrix Electronics and suitable for automotive body electronics, industrial sensor nodes, portable medical monitors, and smart energy meters requiring stable component supply across extended temperature and long-lifecycle programs.
Supply support for LF33CDT 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
STMicroelectronics is a global semiconductor leader headquartered in Geneva, specializing in power management, microcontrollers, and automotive-grade analog ICs.
The LF00 series was designed specifically for low-noise, low-power, and battery-sensitive applications demanding high accuracy, wide temperature operation, and integrated protection - targeting automotive, industrial, and portable equipment markets.
FAQ
What is the minimum input voltage required for regulation at 500 mA load?
The LF33CDT requires a minimum input voltage of 4.3 V to maintain 3.3 V output at 500 mA load, based on its 0.4 V typical dropout specification. Below this threshold, output voltage drops linearly with input; operation below 4.3 V is not guaranteed to regulate.
Can the LF33CDT be used with a 1 µF output capacitor?
No - the datasheet specifies a minimum 2.2 µF ceramic output capacitor with ESR between 0.1 Ω and 10 Ω for guaranteed stability. Using 1 µF risks oscillation or poor transient response, especially under load steps or temperature variation.
Is the INH pin internally pulled up or down?
The INH pin has no internal pull-up or pull-down; it must be actively driven to a valid logic level. A floating INH pin may cause unpredictable enable/disable behavior. External 10 kΩ pull-down is recommended for default-OFF safety in uncontrolled systems.
Does the LF33CDT require an input bypass capacitor?
Yes - a 0.1 µF ceramic capacitor placed close to the IN and GND pins is required per the test circuits in the datasheet. This minimizes high-frequency noise coupling and ensures stable loop response during fast load transients.
LF33CDT Specifications
- Product attributes
- Attribute value
- Manufacturer:
- STMicroelectronics
- Series:
- -
- Package/Case:
- TO-252-3, DPAK (2 Leads + Tab), SC-63
- Packaging:
- Tube
- Product Status:
- Obsolete
- Output Configuration:
- Positive
- Output Type:
- Fixed
- Number of Regulators:
- 1
- Voltage - Input (Max):
- 16V
- Voltage - Output (Min/Fixed):
- 3.3V
- Voltage - Output (Max):
- -
- Voltage Dropout (Max):
- 0.7V @ 500mA
- Current - Output:
- 500mA
- Current - Quiescent (Iq):
- 1 mA
- Current - Supply (Max):
- 12 mA
- PSRR:
- 80dB ~ 65dB (120Hz ~ 65dB)
- Control Features:
- -
- Protection Features:
- Over Current, Over Temperature
- Operating Temperature:
- -40°C ~ 125°C
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- DPAK
LF33CDT FAQ
1.How can I place an order for LF33CDT through Aetrix?
Please submit a Request for Quotation (RFQ) for LF33CDT on Aetrix. Our sales agent will provide a competitive quotation and guide you through the order confirmation once you accept the terms.
2.Are the price and stock information for LF33CDT reliable?
The price and inventory of LF33CDT are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LF33CDT is usually 5 days.
3.What payment methods are accepted for LF33CDT?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LF33CDT transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LF33CDT?
LF33CDT orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LF33CDT order is processed, you will receive an email with the shipment details and tracking number.
Note: Tracking information may take up to 24 hours to appear. Express delivery typically takes 3–5 business days.
5.How can I obtain technical support or documentation for LF33CDT?
For technical support, including LF33CDT datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LF33CDT requirements.
6.How does Aetrix verify that LF33CDT is sourced from the original manufacturer or authorized distributors?
All LF33CDT products on Aetrix are procured from qualified distributors and authorized channels. Our dedicated quality assurance team conducts strict verification, including traceability checks and, if necessary, third-party testing. This ensures that LF33CDT meets industry standards.
7.What is the process for return or replacement of LF33CDT?
All LF33CDT units undergo pre-shipment inspection (PSI). If there is an issue with LF33CDT, returns or replacements are accepted under the following conditions:
1.Quantity discrepancies, incorrect items, or visible external defects (such as breakage or corrosion), acknowledged by Aetrix.
2.The issue is reported within 90 days of delivery.
3.The LF33CDT part is unused and in its original packaging.
Return procedure for LF33CDT:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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