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STMicroelectronics L4957AD3.3TR
- Part No.:
- L4957AD3.3TR
- Manufacturer:
- STMicroelectronics
- Package:
- TO-263-3, D2PAK (2 Leads + Tab), TO-263AB
- Datasheet:
-
L4957AD3.3TR.pdf
- Description:
- IC REG LINEAR 3.3V 5A D2PAK
- Quantity:
- Payment:
- Shipping:
Inventory:4,827
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Product details
Overview
L4957AD3.3TR from STMicroelectronics is a 3.3V fixed-output ultra-low-dropout (ULDO) linear regulator with internal N-channel MOSFET, delivering up to 5A output current, 200mΩ typical RDS(on) at 125°C, and 0.6V max dropout at 2A - designed for post-regulation of SMPS rails in processor I/O and low-voltage memory supplies.
For engineers reviewing the L4957AD3.3TR datasheet, L4957AD3.3TR pinout, L4957AD3.3TR application, or L4957AD3.3TR equivalent, key selection criteria include dropout voltage under high load, thermal shutdown threshold (150°C), ±2% output tolerance across line/load/temperature, quiescent current (0.6–2mA), and D2PAK package thermal resistance (RthJC = 3°C/W).
Technical Context
The L4957AD3.3TR integrates an internal N-channel DMOS pass transistor with 200mΩ typical on-resistance, enabling operation from 3V to 14V input while maintaining regulation down to 0.6V headroom at 2A. Its error amplifier features fast transient response to minimize required output capacitance (22µF minimum).
On-chip trimming ensures ±2% total output voltage tolerance (including line, load, and temperature variation). Thermal shutdown activates at 150°C with 29°C hysteresis, and short-circuit protection limits current to 5.1–7.5A depending on junction temperature.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Output Voltage | 3.3V ±2% (3.234–3.366V) over 0.1A–5A load, 3.3V–5V input, TJ = 0–125°C - ensures stable logic rail for 3.3V systems. |
| Dropout Voltage | 0.6V max at 2A - enables regulation from 3.9V input to 3.3V output, critical for low-headroom SMPS post-regulation. |
| RDS(on) | 200mΩ typical at TJ = 125°C - reduces conduction loss and thermal rise under full 5A load. |
| Quiescent Current | 0.6–2mA over 3V–14V input - maintains efficiency across wide input range without load-dependent bias increase. |
| Ripple Rejection | 60–75dB at 120Hz (ΔVIN = 2VPP) - suppresses switching noise from upstream DC-DC converters. |
| Thermal Shutdown | 150°C activation with 29°C hysteresis - prevents permanent damage during sustained overload or poor heatsinking. |
| Current Limit | 5.1–7.5A (typical 6.3A) - provides robust short-circuit protection while allowing brief inrush currents. |
Pinout & Package
Supplied in D2PAK (TO-263) package: surface-mount, 3-pin, exposed drain pad for thermal dissipation (RthJC = 3°C/W). Pin 1 = IN, Pin 2 = GND, Pin 3 = OUT.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| IN (Pin 1) | Unregulated input supply | Must be bypassed with ≥10µF capacitor; accepts 3–14V input; feeds internal charge pump and pass transistor gate drive. |
| GND (Pin 2) | Reference ground connection | Common return for feedback network and internal circuitry; ties output voltage reference to system ground. |
| OUT (Pin 3) | Regulated output terminal | Delivers 3.3V @ up to 5A; requires ≥22µF output capacitor for stability across all load conditions. |
Key Features
| Feature | Design Value |
|---|---|
| Ultra-low dropout | 0.6V max at 2A enables use with tight-input-margin SMPS outputs (e.g., 3.9V → 3.3V). |
| High-current capability | 5A continuous output supports demanding processor I/O and chipset rails without external parallel devices. |
| Tight output tolerance | ±2% total accuracy (line/load/temp) eliminates need for external trimming in most 3.3V logic applications. |
| Fast transient response | Minimizes required output capacitance to 22µF, reducing board space and cost vs. legacy LDOs requiring >100µF. |
| Integrated protection | Thermal shutdown + current limiting + short-circuit protection enable robust operation without external circuitry. |
Applications
| Motherboard Core Power | Processor I/O Supply |
|---|---|
Use Scenario: Providing clean 3.3V rail to PCIe slot interface circuitry on ATX motherboards. IC Role / Device Role / Timing Role: Post-regulator converting 5V or 3.3V SMPS output to tightly regulated 3.3V for signal integrity. Use Value: 0.6V dropout allows direct use of 3.9V intermediate rail; ±2% tolerance meets PCIe specification for I/O voltage. |
Use Scenario: Supplying 3.3V to CPU I/O buffers and memory controller interfaces in embedded x86 platforms. IC Role / Device Role / Timing Role: Low-noise local regulator decoupling high-speed digital I/O from noisy system power planes. Use Value: 75dB ripple rejection at 120Hz suppresses switching artifacts from primary DC-DC, preserving signal timing margins. |
| Low-Voltage Memory Supply | Graphics Card Auxiliary Rail |
Use Scenario: Delivering 3.3V to DDR2/DDR3 memory termination (SSTL_18/15) and VTT reference circuits. IC Role / Device Role / Timing Role: Precision voltage source for memory bus termination networks requiring stable reference. Use Value: 22µF minimum output cap enables compact layout near memory modules; fast transient response handles burst current demands. |
Use Scenario: Generating 3.3V auxiliary power for GPU display interface logic (DP/HDMI PHY, EDID EEPROM) on discrete graphics cards. IC Role / Device Role / Timing Role: Dedicated low-noise regulator isolating display subsystem from GPU core power noise. Use Value: D2PAK thermal performance (RthJC = 3°C/W) sustains 3A+ loads in constrained card-edge thermal environments. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar ULDO linear regulator applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LD1085V33 | 3.3V fixed, 3A rated, 1.3V dropout at 3A, TO-220 package, RthJA = 50°C/W | Lower current capacity and higher dropout limit use to lower-power peripherals only | Select when board space permits TO-220 mounting and thermal budget allows higher ambient rise. |
| TPS7A4701RGWR | 3.3V adjustable via resistor divider, 1A max, 300mV dropout at 1A, WQFN-20 package | Not pin-compatible; lacks 5A capability and integrated short-circuit protection | Choose only for low-current, space-constrained designs where programmability justifies reduced robustness. |
Compared with LD1085V33 and TPS7A4701RGWR, the L4957AD3.3TR uniquely combines 5A output, sub-1V dropout, D2PAK thermal performance, and full protection integration - making it irreplaceable for high-current motherboard and GPU auxiliary rail applications.
Availability
L4957AD3.3TR is available at Aetrix Electronics and suitable for motherboard power delivery, processor I/O regulation, and low-voltage memory supply applications requiring stable component supply and long-term industrial availability.
Supply support for L4957AD3.3TR 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, Switzerland, specializing in power management, analog, microcontrollers, and automotive ICs.
The L4957A series was developed specifically for high-current, low-dropout post-regulation in computing and communications infrastructure - targeting cost-sensitive, thermally constrained applications where efficiency and reliability outweigh programmability.
FAQ
What is the minimum input voltage required for regulation at full 5A load?
The L4957AD3.3TR requires VIN ≥ (VOUT + VDO) = 3.3V + 0.6V = 3.9V to maintain regulation at 2A; at 5A, dropout rises - datasheet shows ~0.8V at 5A and 125°C, so minimum VIN is 4.1V. Operation below 3V input is prohibited per absolute maximum ratings.
Can the L4957AD3.3TR be used without a heatsink in free-air conditions?
No. With RthJA = 60°C/W and PD ≈ (VIN − 3.3V) × IOUT, even at VIN = 5V and IOUT = 2A, power dissipation is 3.4W - causing >200°C junction rise in free air. A PCB copper pour or heatsink is mandatory for any load >500mA.
Is the 22µF output capacitor value absolute, or can smaller values be used?
The 22µF minimum is required for stability across all operating conditions per Figure 7 and Section 2.2. Using smaller capacitors risks oscillation under dynamic load steps, especially above 1A. Ceramic capacitors must include ESR ≥ 10mΩ or be paralleled with tantalum to meet phase margin requirements.
Does the L4957AD3.3TR support reverse polarity or reverse current protection?
No. The device lacks internal reverse-battery or reverse-current blocking. If input can fall below output (e.g., during hot-swap or standby), an external Schottky diode in series with IN is required to prevent backfeed and potential damage to upstream circuitry.
L4957AD3.3TR Specifications
- Product attributes
- Attribute value
- Manufacturer:
- STMicroelectronics
- Series:
- -
- Package/Case:
- TO-263-3, D2PAK (2 Leads + Tab), TO-263AB
- Packaging:
- Tape & Reel (TR)
- Product Status:
- Obsolete
- Output Configuration:
- Positive
- Output Type:
- Fixed
- Number of Regulators:
- 1
- Voltage - Input (Max):
- 14V
- Voltage - Output (Min/Fixed):
- 3.3V
- Voltage - Output (Max):
- -
- Voltage Dropout (Max):
- -
- Current - Output:
- 5A
- Current - Quiescent (Iq):
- 2 mA
- Current - Supply (Max):
- -
- PSRR:
- 75dB (120Hz)
- Control Features:
- -
- Protection Features:
- Over Temperature, Short Circuit
- Operating Temperature:
- 0°C ~ 125°C
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- D2PAK
L4957AD3.3TR FAQ
1.How can I place an order for L4957AD3.3TR through Aetrix?
Please submit a Request for Quotation (RFQ) for L4957AD3.3TR 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 L4957AD3.3TR reliable?
The price and inventory of L4957AD3.3TR are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for L4957AD3.3TR is usually 5 days.
3.What payment methods are accepted for L4957AD3.3TR?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for L4957AD3.3TR transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for L4957AD3.3TR?
L4957AD3.3TR orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your L4957AD3.3TR 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 L4957AD3.3TR?
For technical support, including L4957AD3.3TR datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your L4957AD3.3TR requirements.
6.How does Aetrix verify that L4957AD3.3TR is sourced from the original manufacturer or authorized distributors?
All L4957AD3.3TR 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 L4957AD3.3TR meets industry standards.
7.What is the process for return or replacement of L4957AD3.3TR?
All L4957AD3.3TR units undergo pre-shipment inspection (PSI). If there is an issue with L4957AD3.3TR, 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 L4957AD3.3TR part is unused and in its original packaging.
Return procedure for L4957AD3.3TR:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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