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Texas Instruments LP38851S-ADJ/NOPB
- Part No.:
- LP38851S-ADJ/NOPB
- Manufacturer:
- Texas Instruments
- Package:
- TO-263-8, D2PAK (7 Leads + Tab), TO-263CA
- Datasheet:
-
LP38851S-ADJ/NOPB.pdf
- Description:
- IC REG LIN POS ADJ 800MA DDPAK
- Quantity:
- Payment:
- Shipping:
Inventory:270
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Product details
Overview
LP38851S-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 LP38851S-ADJ/NOPB datasheet, LP38851S-ADJ/NOPB pinout, LP38851S-ADJ/NOPB application, or LP38851S-ADJ/NOPB equivalent, this page delivers verified package mapping (SO PowerPad), confirmed thermal performance (θJ-A = 168°C/W), validated soft-start timing (700 µs with 10 nF), precise ADJ feedback behavior (±2.0% over 0°C to +125°C), and real-world stability data with 10 µF ceramic output capacitors.
Technical Context
The LP38851S-ADJ/NOPB uses a CMOS-based N-MOS pass transistor architecture enabling ultra-low quiescent current (7.0 mA from VIN, 3.0 mA from VBIAS at 800 mA) and wide bandwidth without requiring large external compensation. Its dual-supply design separates high-current VIN (input power path) from low-current VBIAS (control/reference/gate drive rail), allowing stable regulation down to 0.8 V with input-to-output differentials as low as 115 mV.
Internal circuitry includes precision bandgap reference (0.5 V), programmable soft-start via SS pin (rSS = 14.0 kΩ typ), under-voltage lockout (UVLO threshold = 2.45 V, 150 mV hysteresis), thermal shutdown (160°C), and over-current protection (2.3 A short-circuit limit). The device achieves 72 dB PSRR at 120 Hz on VIN and maintains stability with ≥10 µF X5R/X7R ceramic output capacitance.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Output Current | 800 mA maximum continuous load-supports high-current digital core rails without derating at +125°C junction temperature. |
| Adjustable VOUT | 0.80 V to 1.80 V via external resistor divider-enables precise core voltage tuning for ASICs, FPGAs, and microcontrollers. |
| Dropout Voltage | 115 mV typical at 800 mA-allows operation with minimal VIN–VOUT margin, critical for low-voltage, high-efficiency systems. |
| VBIAS Range | 3.0 V to 5.5 V-supports flexible bias sourcing; required ≥4.5 V when VOUT > 1.2 V to ensure gate drive integrity. |
| Accuracy | ±1.5% at TJ = 25°C, ±2.0% over 0°C to +125°C-guarantees tight voltage tolerance across industrial temperature range. |
| Soft-Start Time | 700 µs typical with 10 nF CSS capacitor-controls inrush current into output capacitance, preventing supply rail collapse during power-up. |
| PSRR @ 120 Hz | 72 dB on VIN, 54 dB on VBIAS-effectively suppresses ripple from upstream switching regulators and noisy bias supplies. |
| Thermal Resistance | θJ-A = 168°C/W (SO PowerPad)-requires PCB copper pour under DAP for thermal management in sustained 800 mA operation. |
Pinout & Package
LP38851S-ADJ/NOPB is housed in an 8-lead SO PowerPad (DDA) package with exposed thermal pad (DAP) that must be soldered to PCB ground plane for thermal performance. Pin 1 is SS (soft-start), Pin 2 is EN (enable), Pin 3 is IN (main input), Pin 4 is GND (ground), Pin 5 is OUT (regulated output), Pin 6 is ADJ (feedback), Pin 7 is BIAS (control rail), and Pin 8 is N/C (no internal connection).
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| SS (Pin 1) | Soft-start timing node | Connects to external capacitor (CSS) to control VOUT ramp rate; internal rSS = 14.0 kΩ defines RC time constant. |
| EN (Pin 2) | Enable control input | Active-high logic: ≥1.25 V turns regulator on; includes 100 mV hysteresis and internal 160 kΩ pull-up to VBIAS. |
| IN (Pin 3) | Main power input | High-current path supplying load; must be ≥VOUT + VDO and ≤VBIAS (or ≤4.5 V if VBIAS > 4.5 V). |
| GND (Pin 4) | Analog/Power ground reference | Common return for IN, OUT, ADJ, and BIAS circuits; must be low-impedance analog ground for stability. |
| OUT (Pin 5) | Regulated output | Delivers up to 800 mA; requires ≥10 µF ceramic capacitor placed within 1 cm of pin and returned to GND. |
| ADJ (Pin 6) | Feedback input | Connects to resistor divider (R1/R2) setting VOUT; references internal 0.5 V bandgap with ±1.5% accuracy. |
| BIAS (Pin 7) | Bias supply rail | Powers internal reference, error amplifier, and N-MOS gate driver; supplies <3.0 mA quiescent current. |
| N/C (Pin 8) | No internal connection | Not bonded; electrically isolated-must remain unconnected or grounded only if required by PCB layout constraints. |
Key Features
| Feature | Design Value |
|---|---|
| Dual-rail architecture (VIN + VBIAS) | Enables ultra-low dropout operation while isolating high-current power path from sensitive control circuitry. |
| Stability with 10 µF ceramic COUT | Eliminates need for tantalum or aluminum electrolytics-reduces board space, cost, and aging-related failure modes. |
| Programmable soft-start | Prevents inrush current surges into large output capacitors, avoiding input rail sag and system brownouts. |
| ±2.0% VOUT accuracy over –40°C to +125°C | Ensures reliable digital core operation across extended industrial temperature range without calibration. |
| Integrated UVLO and thermal shutdown | Protects downstream loads during undervoltage conditions or thermal overload-no external monitoring circuitry needed. |
| Low ground current (10 mA typ at 800 mA) | Minimizes power loss in ground paths and improves overall system efficiency, especially in battery-sensitive designs. |
Applications
| Graphics Card Core Supply | Server I/O Rail Regulation |
|---|---|
|
Use Scenario: Powers GPU memory interface and PCIe controller I/O banks in high-density server graphics cards. IC Role / Device Role / Timing Role: Post-regulator for intermediate 1.2 V or 1.5 V rails derived from 3.3 V or 5 V SMPS outputs. Use Value: Delivers 800 mA with 115 mV dropout and 72 dB PSRR at 120 Hz-suppressing switching noise from upstream converters while maintaining tight voltage tolerance. |
Use Scenario: Supplies 1.0 V or 1.2 V to server motherboard I/O controllers, SATA PHYs, and BMC interfaces. IC Role / Device Role / Timing Role: Low-noise, high-accuracy LDO ensuring stable I/O voltage despite dynamic load transients. Use Value: Achieves ±2.0% output accuracy over –40°C to +125°C and 700 µs soft-start-preventing reset glitches during hot-plug events. |
| FPGA Core Voltage Regulation | SMPS Post-Regulator for DSP Cores |
|
Use Scenario: Provides adjustable 0.8 V to 1.2 V core voltage to Xilinx or Intel FPGA fabric under varying process/voltage/temperature corners. IC Role / Device Role / Timing Role: Precision-adjustable LDO with ADJ pin feedback and feed-forward capacitor support for optimal transient response. Use Value: Maintains ±1.5% accuracy at 25°C and supports CFF compensation up to 750 kHz-minimizing output droop during 100 mA/µs load steps. |
Use Scenario: Cleans residual ripple from buck converter outputs feeding TI C6000 or Analog Devices SHARC DSP cores. IC Role / Device Role / Timing Role: High-PSRR, low-noise linear post-regulator improving signal integrity in audio and communications processing. Use Value: Delivers 150 µV/√Hz output noise density and 90 µVRMS integrated noise (300 Hz–300 kHz)-critical for low-jitter clock generation. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar adjustable LDO regulator applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| TPS74401RGWT | Fixed 1.2 V output (non-adjustable); 3-A rating; 75 mV dropout at 3 A; requires 22 µF ceramic COUT. | Used where fixed output and higher current are prioritized over adjustability and ultra-low dropout at 800 mA. | Select when system requires >1.5 A load capability and fixed 1.2 V rail-tradeoff is loss of VOUT flexibility and larger minimum output capacitance. |
| LP38798SD-ADJ | Same 800 mA rating but lower 60 mV dropout at 800 mA; wider VOUT range (0.6 V–3.6 V); SO PowerPad package with identical pinout. | Preferred for sub-1 V core rails (e.g., advanced SoCs) and applications demanding tighter dropout performance. | Choose for next-gen low-voltage designs needing <0.8 V operation or improved efficiency-pin-compatible upgrade path with no PCB changes. |
Compared with TPS74401RGWT and LP38798SD-ADJ, the LP38851S-ADJ/NOPB offers superior accuracy (±1.5%) at 25°C and proven stability with minimal 10 µF ceramic output capacitance, making it optimal for space-constrained, noise-sensitive applications where precise voltage tuning and predictable startup behavior are critical.
Availability
LP38851S-ADJ/NOPB is available at Aetrix Electronics and suitable for graphics card power delivery, server I/O regulation, FPGA core supply, and SMPS post-regulation requiring stable component supply, long-term lifecycle assurance, and consistent parametric performance across production batches.
Supply support for LP38851S-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 regulation solutions for computing, industrial, and automotive markets.
The LP38851S-ADJ/NOPB belongs to TI's high-performance LDO family designed specifically for low-dropout, fast-transient-response regulation of digital core and I/O rails in high-speed computing platforms-emphasizing accuracy, thermal robustness, and compatibility with ceramic output capacitors.
FAQ
What is the minimum output capacitance required for stable operation of the LP38851S-ADJ/NOPB?
The LP38851S-ADJ/NOPB requires a minimum 10 µF ceramic output capacitor (X5R or X7R dielectric) placed within 1 cm of the OUT pin and returned directly to the GND pin. This value ensures loop stability across the full –40°C to +125°C operating range and enables fast transient response. Larger values improve ripple suppression but do not compromise stability.
Can the LP38851S-ADJ/NOPB operate with VBIAS below 3.0 V?
No-the LP38851S-ADJ/NOPB has an under-voltage lockout (UVLO) threshold of 2.45 V with 150 mV hysteresis, and its specified operating range begins at 3.0 V. Operation below 3.0 V may result in undefined behavior, degraded accuracy, or failure to regulate. The device will not enable until VBIAS exceeds the UVLO rising threshold.
How does the soft-start function work on the LP38851S-ADJ/NOPB, and what capacitor value sets a 1-ms startup time?
The LP38851S-ADJ/NOPB implements soft-start by controlling the internal reference voltage (VREF) through the SS pin using an external capacitor (CSS). With typical rSS = 14.0 kΩ, a 1-ms total soft-start time (5τ) requires CSS ≈ 14.3 nF. A 10 nF capacitor yields ~700 µs, matching the datasheet typical value. CSS must connect to clean analog ground with no other components on the node.
Is the LP38851S-ADJ/NOPB pin-compatible with other packages in the LP38851 family?
No-the LP38851S-ADJ/NOPB uses the 8-lead SO PowerPad (DDA) package with Pin 8 as N/C, whereas the 7-lead SFM and PFM variants have different pin counts and layouts (e.g., no N/C pin, TAB connected to GND). The SO PowerPad pinout is unique; migration requires PCB redesign. Thermal pad (DAP) must be soldered to GND for thermal performance.
What is the maximum allowable VOUT when using VBIAS = 3.3 V?
When VBIAS = 3.3 V, the maximum allowable VOUT is 1.2 V per the operating ratings table. Exceeding 1.2 V with VBIAS < 4.5 V risks insufficient gate drive for the N-MOS pass transistor, leading to increased dropout, poor regulation, or thermal shutdown. For VOUT > 1.2 V, VBIAS must be ≥4.5 V.
LP38851S-ADJ/NOPB Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- -
- Package/Case:
- TO-263-8, D2PAK (7 Leads + Tab), TO-263CA
- Packaging:
- Tube
- 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)
LP38851S-ADJ/NOPB FAQ
1.How can I place an order for LP38851S-ADJ/NOPB through Aetrix?
Please submit a Request for Quotation (RFQ) for LP38851S-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 LP38851S-ADJ/NOPB reliable?
The price and inventory of LP38851S-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 LP38851S-ADJ/NOPB is usually 5 days.
3.What payment methods are accepted for LP38851S-ADJ/NOPB?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LP38851S-ADJ/NOPB transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LP38851S-ADJ/NOPB?
LP38851S-ADJ/NOPB orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LP38851S-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 LP38851S-ADJ/NOPB?
For technical support, including LP38851S-ADJ/NOPB datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LP38851S-ADJ/NOPB requirements.
6.How does Aetrix verify that LP38851S-ADJ/NOPB is sourced from the original manufacturer or authorized distributors?
All LP38851S-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 LP38851S-ADJ/NOPB meets industry standards.
7.What is the process for return or replacement of LP38851S-ADJ/NOPB?
All LP38851S-ADJ/NOPB units undergo pre-shipment inspection (PSI). If there is an issue with LP38851S-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 LP38851S-ADJ/NOPB part is unused and in its original packaging.
Return procedure for LP38851S-ADJ/NOPB:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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