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Texas Instruments LP38851SX-ADJ/NOPB
- Part No.:
- LP38851SX-ADJ/NOPB
- Manufacturer:
- Texas Instruments
- Package:
- TO-263-8, D2PAK (7 Leads + Tab), TO-263CA
- Datasheet:
-
LP38851SX-ADJ/NOPB.pdf
- Description:
- IC REG LIN POS ADJ 800MA DDPAK
- Quantity:
- Payment:
- Shipping:
Inventory:956
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Product details
Overview
LP38851SX-ADJ/NOPB from Texas Instruments is an 800 mA adjustable LDO linear regulator with dual-rail operation (VIN and VBIAS), fast transient response, ±1.5% output voltage accuracy at 25°C, 115 mV typical dropout at full load, and integrated soft-start and enable functions-designed for powering DSP/FPGA core rails and SMPS post-regulation in graphics cards and servers.
For engineers reviewing the LP38851SX-ADJ/NOPB datasheet, LP38851SX-ADJ/NOPB pinout, LP38851SX-ADJ/NOPB application, or LP38851SX-ADJ/NOPB equivalent, key selection considerations include its dual-supply architecture (VIN + VBIAS), ceramic-capacitor stability (10 µF min), ultra-low ground current (7 mA typ. from VIN at 800 mA), and thermal shutdown at 160°C.
Technical Context
The LP38851SX-ADJ/NOPB uses a CMOS-based N-MOS pass transistor architecture enabling wide bandwidth and low quiescent current across load range, while separating power path (VIN → OUT) from control biasing (VBIAS → internal reference/gate drive). Its dual-rail design allows operation with VIN as low as VOUT + 115 mV when VBIAS ≥ 3.0 V.
Stability is achieved with minimal external components: only 10 µF ceramic output capacitance is required, and feed-forward compensation (CFF) is optional for enhanced load transient response above 0.8 VOUT. Soft-start timing is programmable via external CSS (700 µs typical with 10 nF), controlled by internal 14 kΩ SS-pin resistance.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Output Current | 800 mA maximum continuous - supports high-current digital core rails without derating at TJ ≤ 125°C. |
| Adjustable VOUT Range | 0.80 V to 1.80 V - set via external resistor divider on ADJ pin; enables precise core voltage tuning for ASICs, FPGAs, and DSPs. |
| Dropout Voltage | 115 mV typical at 800 mA - enables regulation from ultra-low VIN (e.g., 0.915 V when VOUT = 0.8 V), critical for post-regulation after buck converters. |
| VBIAS Operating Range | 3.0 V to 5.5 V - supplies gate drive and control circuitry; range depends on VOUT: 3.0–5.5 V if VOUT ≤ 1.2 V, 4.5–5.5 V if VOUT > 1.2 V. |
| Output Voltage Accuracy | ±1.5% at TJ = 25°C, ±2.0% over 0°C to +125°C - ensures stable core supply under thermal stress in server and embedded applications. |
| PSRR @ 1 kHz | 61 dB for VIN ripple, 53 dB for VBIAS ripple - suppresses switching noise from upstream SMPS, improving signal integrity in sensitive digital loads. |
| Thermal Shutdown | 160°C junction temperature with 10°C hysteresis - protects device during overload or poor heatsinking; SO PowerPad package enables θJ-C = 11°C/W. |
Pinout & Package
LP38851SX-ADJ/NOPB is packaged in an 8-lead SO PowerPad (DDA) thermally enhanced surface-mount package with exposed DAP (Die Attach Pad) connected to GND for improved heat dissipation. The DAP is electrically isolated from all pins and must be soldered to a PCB ground plane.
| Pin | Circuit Role | Design Meaning |
|---|---|---|
| 1 | SS | Soft-start capacitor connection; controls VOUT ramp rate via internal 14 kΩ resistor - enables inrush current limiting during power-up. |
| 2 | EN | Enable input; active-high logic (VEN(ON) = 1.25 V typ.) with 100 mV hysteresis - allows system-level power sequencing and standby control. |
| 3 | IN | Main power input; supplies current to load - must be ≥ VOUT + 115 mV and ≤ VBIAS (or ≤ 4.5 V if VBIAS > 4.5 V). |
| 4 | GND | Analog ground reference; return path for IN, BIAS, and ADJ - requires low-impedance connection to minimize noise coupling. |
| 5 | OUT | Regulated output; delivers up to 800 mA - must be decoupled with ≥10 µF ceramic capacitor placed within 1 cm of pin. |
| 6 | ADJ | Feedback node; connects to resistor divider (R1/R2) setting VOUT = 0.5 V × (1 + R1/R2) - high-impedance input requiring tight-tolerance resistors. |
| 7 | BIAS | Bias supply rail; powers internal reference and N-MOS gate driver - separates control logic from power path, enabling ultra-low VIN operation. |
| 8 | N/C | No internal connection - left unconnected; not used for thermal or electrical function. |
Key Features
| Feature | Design Value |
|---|---|
| Dual-rail supply architecture | VIN handles high-current load delivery; VBIAS powers low-current control circuitry - enables operation with VIN as low as VOUT + 115 mV. |
| Ceramic-capacitor stability | Stable with ≥10 µF X5R/X7R ceramic output capacitor - eliminates need for ESR-tuned tantalum, reducing BOM cost and board space. |
| Programmable soft-start | RC-controlled VOUT ramp using external CSS (e.g., 10 nF → 700 µs typical) - prevents inrush current damage to downstream capacitors and ICs. |
| Ultra-low ground current | 7.0 mA typical from VIN at 800 mA load - minimizes wasted power in battery- or efficiency-sensitive systems like notebooks and graphics cards. |
| High PSRR at 1 kHz | 61 dB rejection of VIN ripple - effectively filters switching noise from upstream DC/DC converters in multi-rail power architectures. |
Applications
| ASIC Core Supply | SMPS Post-Regulator |
|---|---|
|
Use Scenario: Powers CPU/GPU core voltage rails in desktops, notebooks, and graphics cards where tight voltage tolerance and fast load transients are required. IC Role / Device Role / Timing Role: Primary low-noise, high-accuracy LDO delivering stable 0.8–1.2 V to digital logic cores with <1.5% initial accuracy and <2% variation over temperature. Use Value: Enables reliable operation of high-speed processors under dynamic load changes (e.g., GPU burst activity), leveraging 800 mA capability and 61 dB PSRR to suppress SMPS ripple. |
Use Scenario: Final-stage regulation after a high-efficiency buck converter in server I/O or FPGA power trees. IC Role / Device Role / Timing Role: Precision post-regulator correcting residual ripple and drift from upstream switching stages; maintains VOUT within ±2% across line/load/temperature. Use Value: Delivers clean, low-noise 0.8–1.8 V output with 115 mV dropout - allowing tighter VIN margins and higher overall system efficiency than single-stage LDO solutions. |
| FPGA I/O Bank Supply | Server Memory Subsystem |
|
Use Scenario: Supplies configurable I/O banks in Xilinx/Intel FPGAs requiring multiple independent, tightly regulated voltages (e.g., 1.2 V, 1.5 V, 1.8 V). IC Role / Device Role / Timing Role: Adjustable LDO configured per bank via R1/R2 feedback network; soft-start prevents simultaneous inrush across multiple banks. Use Value: Supports flexible voltage scaling with ±1.5% accuracy at 25°C and 10 µF ceramic stability - simplifies layout and reduces component count versus fixed-output alternatives. |
Use Scenario: Powers DDR4/DDR5 memory termination and auxiliary rails in enterprise servers where thermal reliability and long-term stability are critical. IC Role / Device Role / Timing Role: High-current (800 mA), high-temperature (−40°C to +125°C TJ) LDO with thermal shutdown (160°C) and over-current protection. Use Value: Ensures uninterrupted memory subsystem operation under sustained load and elevated ambient temperatures, aided by SO PowerPad's 11°C/W θJ-C thermal path. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar adjustable LDO regulator applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| TPS7A8101DRBR | Single-rail (VIN-only) 1 A LDO; 150 mV dropout at 1 A; requires ≥22 µF output capacitance; no VBIAS rail. | Less suitable for ultra-low-VIN post-regulation; better for simpler single-supply systems without bias rail constraints. | Choose TPS7A8101DRBR when board space permits larger output caps and VBIAS routing is impractical. |
| LP3985IM5-1.8/NOPB | Fixed 1.8 V output; 150 mA max; SOT-23-5; 160 mV dropout; no soft-start or enable; ±2% accuracy over temperature. | Limited to low-current, fixed-voltage use cases (e.g., peripheral I/O); lacks adjustability, sequencing, and thermal robustness. | Choose LP3985IM5-1.8/NOPB only for cost-sensitive, low-power fixed-voltage rails where 800 mA and precision are unnecessary. |
Compared with TPS7A8101DRBR and LP3985IM5-1.8/NOPB, LP38851SX-ADJ/NOPB uniquely supports dual-rail operation enabling lower VIN headroom, offers higher accuracy (±1.5% vs ±2%), and integrates soft-start and enable - making it optimal for high-performance, thermally demanding digital core supplies.
Availability
LP38851SX-ADJ/NOPB is available at Aetrix Electronics and suitable for graphics card power delivery, FPGA core regulation, and server I/O supply applications requiring stable component supply, long-lifecycle support, and traceable sourcing.
Supply support for LP38851SX-ADJ/NOPB 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 leader specializing in analog, embedded processing, and power management ICs, with decades of expertise in high-reliability power solutions for computing and industrial markets.
The LP38851 series belongs to TI's high-accuracy, fast-response LDO family designed specifically for powering advanced digital loads-including DSP, FPGA, and ASIC cores-where low dropout, tight regulation, and robust transient performance are mandatory.
FAQ
What is the minimum input voltage required for LP38851SX-ADJ/NOPB to regulate at 0.8 V output?
The LP38851SX-ADJ/NOPB requires VIN ≥ VOUT + VDO, where VDO is 115 mV typical at 800 mA. For 0.8 V output, minimum VIN is 0.915 V (typical). However, VIN must also be ≤ VBIAS and ≤ 4.5 V if VBIAS exceeds 4.5 V. At VOUT = 0.8 V, VBIAS may be as low as 3.0 V, so VIN can operate down to 0.915 V while remaining within spec. This ultra-low VIN capability is enabled by the dual-rail architecture separating power (VIN) and control (VBIAS) paths.
Can LP38851SX-ADJ/NOPB operate with only a single supply rail?
No - LP38851SX-ADJ/NOPB requires two independent supply rails: VIN (main power input) and VBIAS (control/bias supply). VBIAS powers the internal reference, error amplifier, and N-MOS gate driver, and must be within 3.0–5.5 V depending on VOUT. Using only one rail violates the operating conditions specified in the datasheet and will prevent regulation. The dual-rail design is fundamental to its low-dropout and low-quiescent-current performance.
What output capacitor types are compatible with LP38851SX-ADJ/NOPB?
LP38851SX-ADJ/NOPB is stable with ≥10 µF ceramic capacitors (X5R or X7R dielectrics recommended); tantalum capacitors also provide stable operation but may exhibit ESR-related voltage deviations during fast load transients. Aluminum electrolytics are not recommended below 0°C due to ESR rise. The device does not require ESR for stability, unlike older LDOs - enabling smaller, more reliable ceramic solutions and eliminating ESR tolerance concerns in design.
How is the output voltage set on LP38851SX-ADJ/NOPB?
LP38851SX-ADJ/NOPB uses an external resistor divider on the ADJ pin to set VOUT per the formula VOUT = 0.5 V × (1 + R1/R2). The internal reference is 0.5 V, and ADJ is a high-impedance node. TI provides Table 1 in the datasheet with optimized ±1% resistor pairs (e.g., R1 = 1.40 kΩ, R2 = 1.00 kΩ for 1.2 V) and CFF values to ensure stability and transient performance. Resistor parallel impedance must remain ≤10 kΩ to avoid parasitic effects.
Does LP38851SX-ADJ/NOPB include over-temperature protection?
Yes - LP38851SX-ADJ/NOPB incorporates thermal shutdown that activates at 160°C junction temperature (TSD), with 10°C hysteresis (TSD(HYS)). When triggered, the output is disabled until junction temperature falls below 150°C. This protection is independent of other fault conditions and operates regardless of EN or VBIAS state. The SO PowerPad package (used in LP38851SX-ADJ/NOPB) provides θJ-C = 11°C/W, facilitating effective heatsinking to delay or prevent thermal shutdown under sustained 800 mA loads.
LP38851SX-ADJ/NOPB Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- -
- Package/Case:
- TO-263-8, D2PAK (7 Leads + Tab), TO-263CA
- Packaging:
- Tape & Reel (TR)
- Product Status:
- Active
- Output Configuration:
- Positive
- Output Type:
- Adjustable
- Number of Regulators:
- 1
- Voltage - Input (Max):
- 5.5V
- Voltage - Output (Min/Fixed):
- 0.8V
- Voltage - Output (Max):
- 1.8V
- Voltage Dropout (Max):
- 0.2V @ 800mA
- Current - Output:
- 800mA
- Current - Quiescent (Iq):
- 300 µA
- Current - Supply (Max):
- 9 mA
- PSRR:
- 72dB ~ 61dB (120Hz ~ 1kHz)
- Control Features:
- Enable, Soft Start
- Protection Features:
- Over Current, Over Temperature, Short Circuit, Under Voltage Lockout (UVLO)
- Operating Temperature:
- -40°C ~ 125°C
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- TO-263 (DDPAK-7)
LP38851SX-ADJ/NOPB FAQ
1.How can I place an order for LP38851SX-ADJ/NOPB through Aetrix?
Please submit a Request for Quotation (RFQ) for LP38851SX-ADJ/NOPB 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 LP38851SX-ADJ/NOPB reliable?
The price and inventory of LP38851SX-ADJ/NOPB are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LP38851SX-ADJ/NOPB is usually 5 days.
3.What payment methods are accepted for LP38851SX-ADJ/NOPB?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LP38851SX-ADJ/NOPB transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LP38851SX-ADJ/NOPB?
LP38851SX-ADJ/NOPB orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LP38851SX-ADJ/NOPB 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 LP38851SX-ADJ/NOPB?
For technical support, including LP38851SX-ADJ/NOPB datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LP38851SX-ADJ/NOPB requirements.
6.How does Aetrix verify that LP38851SX-ADJ/NOPB is sourced from the original manufacturer or authorized distributors?
All LP38851SX-ADJ/NOPB 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 LP38851SX-ADJ/NOPB meets industry standards.
7.What is the process for return or replacement of LP38851SX-ADJ/NOPB?
All LP38851SX-ADJ/NOPB units undergo pre-shipment inspection (PSI). If there is an issue with LP38851SX-ADJ/NOPB, 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 LP38851SX-ADJ/NOPB part is unused and in its original packaging.
Return procedure for LP38851SX-ADJ/NOPB:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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