My Inquiry
My Account
Texas Instruments LP38851MR-ADJ/NOPB
- Part No.:
- LP38851MR-ADJ/NOPB
- Manufacturer:
- Texas Instruments
- Package:
- 8-PowerSOIC (0.154", 3.90mm Width)
- Datasheet:
-
LP38851MR-ADJ/NOPB.pdf
- Description:
- IC REG LIN POS ADJ 800MA 8SO
- Quantity:
- Payment:
- Shipping:
Inventory:1,386
Please send an inquiry. Send us your inquiry, and we will respond immediately.
Product details
Overview
LP38851MR-ADJ/NOPB from Texas Instruments is an 800 mA adjustable LDO linear regulator with dual-rail operation (VIN and VBIAS), 115 mV typical dropout at full load, ±1.5% VADJ accuracy at 25°C, and programmable soft-start. It delivers stable core voltage for DSPs and microcontrollers in low-VIN post-regulation applications where ultra-low dropout and fast transient response are critical.
For engineers reviewing the LP38851MR-ADJ/NOPB datasheet, LP38851MR-ADJ/NOPB pinout, LP38851MR-ADJ/NOPB application, or LP38851MR-ADJ/NOPB equivalent, this page provides verified package mapping (SO PowerPad-8), confirmed pin functions (including SS, EN, ADJ, BIAS), thermal performance data (θJ-A = 168°C/W), and real-world design implications of its CMOS N-MOS architecture and dual-supply biasing.
Technical Context
The LP38851MR-ADJ/NOPB uses a CMOS-based N-MOS pass transistor architecture, enabling ultra-low quiescent current (7.0 mA typical from VIN, 3.0 mA from VBIAS at 800 mA) and wide bandwidth without requiring large output capacitance. Its dual-input structure separates power delivery (VIN) from control circuitry biasing (VBIAS), allowing operation down to VIN = VOUT + 115 mV while maintaining regulation even when VIN falls below VBIAS.
It integrates internal UVLO (2.45 V threshold, 150 mV hysteresis), thermal shutdown (160°C), over-current protection, and a precision 500 mV reference. Soft-start is implemented via external CSS connected to the SS pin, with internal rSS = 14.0 kΩ (typical), enabling controlled VOUT ramp-up independent of load capacitance value.
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 with proper heatsinking. |
| Dropout Voltage | 115 mV typical at 800 mA - enables regulation from VIN as low as VOUT + 0.115 V, critical for battery-powered or SMPS post-regulator use. |
| VADJ Accuracy | ±1.5% at TJ = 25°C, ±2.0% over 0°C to +125°C - ensures tight output tolerance across temperature for precision core supplies. |
| Stability | Stable with ≥10 µF ceramic output capacitor (X5R/X7R) - eliminates need for ESR-tuned tantalum, simplifying BOM and improving reliability. |
| VBIAS Range | 3.0 V to 5.5 V (for VOUT ≤ 1.2 V); 4.5 V to 5.5 V (for VOUT > 1.2 V) - defines minimum bias rail requirements for gate drive and reference stability. |
| Soft-Start Time | 700 µs typical with 10 nF CSS - limits inrush current into COUT during power-up, preventing supply rail collapse in multi-rail systems. |
| PSRR @ 1 kHz | 61 dB (VIN ripple), 53 dB (VBIAS ripple) - suppresses switching noise from upstream SMPS or noisy bias rails, preserving signal integrity. |
Pinout & Package
LP38851MR-ADJ/NOPB is packaged in an 8-lead SO PowerPad (DDA) with exposed thermal pad (DAP) soldered to PCB ground for enhanced heat dissipation. The DAP is electrically isolated and serves thermal-only function per TI documentation.
| Pin | Circuit Role | Design Meaning |
|---|---|---|
| 1 | SS | Soft-start timing node - connects to external CSS; controls VOUT ramp rate via internal 14 kΩ resistor. |
| 2 | EN | Enable input - active-high logic (1.25 V threshold); internal 160 kΩ pull-up to VBIAS enables default-on operation if left open. |
| 3 | IN | Main power input - supplies current to load; must be ≥ VOUT + VDO and ≤ VBIAS (or ≤ 4.5 V if VBIAS > 4.5 V). |
| 4 | GND | Analog ground reference - return path for IN, OUT, and ADJ; must be low-impedance and separated from power ground where possible. |
| 5 | OUT | Regulated output - delivers up to 800 mA; requires ≥10 µF ceramic capacitor placed within 1 cm of pin and returned to GND. |
| 6 | ADJ | Feedback input - connects to resistor divider (R1/R2) setting VOUT = 0.5 V × (1 + R1/R2); high-impedance node sensitive to leakage. |
| 7 | BIAS | Bias supply rail - powers internal reference, error amplifier, and gate driver; must meet voltage range per VOUT setting. |
| 8 | N/C | No internal connection - electrically floating; no routing or component attachment required. |
Key Features
| Feature | Design Value |
|---|---|
| Dual-rail input architecture | Separates high-current VIN path from low-current VBIAS control rail - enables ultra-low VIN operation while maintaining gate drive strength and reference stability. |
| CMOS N-MOS pass element | Eliminates body diode conduction - prevents reverse current flow during VIN dropout or hot-swap events unless EN and VBIAS are active. |
| Programmable soft-start | External CSS sets precise turn-on time (700 µs typ. with 10 nF) - avoids system reset due to inrush-induced brownout on shared VCC rails. |
| Ultra-low ground current | 7.0 mA (VIN) + 3.0 mA (VBIAS) at 800 mA load - reduces wasted power in portable and thermally constrained applications. |
| Wide temperature operation | Specified from −40°C to +125°C junction - supports industrial, automotive under-hood, and server CPU/GPU core supply environments. |
Applications
| ASIC Core Supply | DSP/FPGA Core Rail |
|---|---|
|
Use Scenario: Powering 0.9–1.2 V cores in desktop GPU ASICs with tight voltage tolerance and fast load transients. IC Role / Device Role / Timing Role: Primary post-regulator delivering clean, low-noise VDD_CORE with <2% line/load regulation and sub-µs transient recovery. Use Value: Enables reliable operation at 1.2 V ±12 mV across temperature, avoiding timing violations caused by SMPS ripple or droop. |
Use Scenario: Supplying configurable logic and DSP blocks in Xilinx/Altera FPGAs requiring 0.8–1.1 V with soft-start sequencing. IC Role / Device Role / Timing Role: Adjustable LDO providing precise, sequenced core voltage with programmable ramp time to prevent configuration errors. Use Value: Eliminates need for external sequencing ICs; CSS-controlled soft-start ensures safe FPGA configuration before clock enable. |
| SMPS Post-Regulator | Server I/O Supply |
|
Use Scenario: Tightening output of 3.3 V buck converter feeding 1.8 V I/O banks in high-speed SerDes interfaces. IC Role / Device Role / Timing Role: Low-noise, high-PSRR post-regulator suppressing switching artifacts above 100 kHz to meet jitter specs. Use Value: Achieves 53 dB PSRR at 1 kHz on VBIAS rail and 61 dB on VIN - reduces deterministic jitter induced by SMPS switching noise. |
Use Scenario: Delivering 1.0–1.5 V to PCIe switch I/O buffers in enterprise servers with strict thermal and reliability requirements. IC Role / Device Role / Timing Role: High-current, thermally robust LDO with integrated thermal shutdown (160°C) and over-current protection. Use Value: Maintains regulation under sustained 800 mA loads at +105°C ambient using SO PowerPad's 11°C/W θJ-C path to PCB copper. |
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 input (no VBIAS), 1 A output, 150 mV dropout at 1 A, ±2% VREF accuracy over temp. | Lacks dual-rail flexibility; cannot operate below VOUT + 150 mV without VBIAS assist; higher quiescent current (2.5 mA vs 3.0 mA total). | Choose for simpler single-supply systems where VIN ≥ VOUT + 0.15 V and VBIAS rail is unavailable. |
| TPS74801DRCR | Adjustable 1.5 A LDO with VBIAS, 130 mV dropout at 1.5 A, ±1% VREF, but requires ≥22 µF output capacitance. | Higher current capability but mandates larger ceramic or tantalum output cap; less optimal for space-constrained designs needing only 800 mA. | Choose when >1 A load current or tighter ±1% accuracy is required, accepting larger COUT footprint and higher cost. |
Compared with TPS7A8101DRBR and TPS74801DRCR, LP38851MR-ADJ/NOPB uniquely balances ultra-low dropout (115 mV), dual-rail operation, and minimal 10 µF ceramic stability - making it optimal for compact, low-VIN post-regulation where bias rail availability allows architectural flexibility.
Availability
LP38851MR-ADJ/NOPB is available at Aetrix Electronics and suitable for ASIC core supplies, DSP/FPGA power rails, SMPS post-regulators, server I/O supplies, and industrial embedded controllers requiring stable component supply with guaranteed long-term sourcing.
Supply support for LP38851MR-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 designing analog, embedded processing, and connectivity solutions for industrial, automotive, and communications markets.
LP38851MR-ADJ/NOPB belongs to TI's high-performance LDO portfolio targeting low-noise, fast-transient digital core supplies - engineered specifically for post-regulation in multi-rail systems where VIN headroom is limited and bias rail isolation improves PSRR.
FAQ
What is the minimum input voltage required for LP38851MR-ADJ/NOPB to regulate at 1.0 V output?
The minimum input voltage is determined by dropout voltage: VIN(MIN) = VOUT + VDO. For LP38851MR-ADJ/NOPB at 1.0 V output and 800 mA load, typical dropout is 115 mV, so VIN(MIN) = 1.115 V. However, VIN must also be ≤ VBIAS (and ≤ 4.5 V if VBIAS > 4.5 V). For VOUT = 1.0 V, VBIAS may be 3.0–5.5 V, so practical VIN range is 1.115 V to VBIAS.
Can LP38851MR-ADJ/NOPB operate with only one supply rail?
No - LP38851MR-ADJ/NOPB requires two independent supplies: VIN (power path to load) and VBIAS (control/reference bias rail). The device will not function if VBIAS is absent or below UVLO (2.45 V), even if VIN is present. This dual-rail architecture is fundamental to its low-dropout and low-quiescent-current operation.
What is the purpose of the N/C pin (Pin 8) on LP38851MR-ADJ/NOPB?
Pin 8 is designated N/C (No internal connection) in the LP38851MR-ADJ/NOPB SO PowerPad package. It is electrically isolated from all internal circuitry and must remain unconnected. Routing traces or placing components on this pin risks mechanical interference or unintended coupling; TI explicitly states it has no functional role in LP38851MR-ADJ/NOPB operation.
How does the soft-start function of LP38851MR-ADJ/NOPB interact with the enable pin?
Soft-start activation in LP38851MR-ADJ/NOPB requires both conditions: VBIAS must rise above UVLO (2.45 V) AND EN must exceed VEN(ON) (1.25 V). If either condition fails, the SS pin remains grounded and VOUT stays at 0 V. Once both are met, internal rSS (14 kΩ) charges external CSS, ramping VREF and thus VOUT exponentially - ensuring controlled turn-on only when full system readiness is confirmed.
Is LP38851MR-ADJ/NOPB compatible with 100 % ceramic output capacitors?
Yes - LP38851MR-ADJ/NOPB is explicitly characterized and specified for stability with ≥10 µF X5R or X7R ceramic capacitors at the output. Unlike many older LDOs, it does not require ESR-based compensation; its CMOS N-MOS architecture and internal compensation eliminate dependency on capacitor ESR, enabling smaller, more reliable, and temperature-stable ceramic-only designs.
LP38851MR-ADJ/NOPB Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- -
- Package/Case:
- 8-PowerSOIC (0.154", 3.90mm Width)
- 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:
- 8-SO PowerPad
LP38851MR-ADJ/NOPB FAQ
1.How can I place an order for LP38851MR-ADJ/NOPB through Aetrix?
Please submit a Request for Quotation (RFQ) for LP38851MR-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 LP38851MR-ADJ/NOPB reliable?
The price and inventory of LP38851MR-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 LP38851MR-ADJ/NOPB is usually 5 days.
3.What payment methods are accepted for LP38851MR-ADJ/NOPB?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LP38851MR-ADJ/NOPB transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LP38851MR-ADJ/NOPB?
LP38851MR-ADJ/NOPB orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LP38851MR-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 LP38851MR-ADJ/NOPB?
For technical support, including LP38851MR-ADJ/NOPB datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LP38851MR-ADJ/NOPB requirements.
6.How does Aetrix verify that LP38851MR-ADJ/NOPB is sourced from the original manufacturer or authorized distributors?
All LP38851MR-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 LP38851MR-ADJ/NOPB meets industry standards.
7.What is the process for return or replacement of LP38851MR-ADJ/NOPB?
All LP38851MR-ADJ/NOPB units undergo pre-shipment inspection (PSI). If there is an issue with LP38851MR-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 LP38851MR-ADJ/NOPB part is unused and in its original packaging.
Return procedure for LP38851MR-ADJ/NOPB:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
LP38851MR-ADJ/NOPB Tags
-
MIC5504-1.8YM5-TR
Microchip Technology
-
MIC5504-3.3YM5-TR
Microchip Technology
-
MIC5365-3.0YC5-TR
Microchip Technology
-
MIC5365-1.8YC5-TR
Microchip Technology
-
MIC5365-2.5YC5-TR
Microchip Technology
-
MIC5365-3.3YC5-TR
Microchip Technology
-
MIC5365-3.3YD5-TR
Microchip Technology
-
MIC5317-3.3YM5-TR
Microchip Technology
-
TLV1117LV33DCYR
Texas Instruments
-
MIC5317-3.3YMT-TZ
Microchip Technology
-
MIC5528-3.3YMT-TR
Microchip Technology
-
TLV75801PDRVR
Texas Instruments
Tech Hub
A D latch stores one bit while Enable controls when data can pass. This reference covers gate-level operation, truth tables, transparency, setup and hold timing, LE versus OE, common ICs and practical …
An SR latch stores one bit through cross-coupled feedback. This engineering reference covers NOR and NAND implementations, truth tables, forbidden-state recovery, gated operation, switch debouncing, fa…
Latch circuits retain one bit through feedback. This technical reference covers SR and D latches, truth tables, transparency, timing limits, latch-versus-flip-flop behavior, applications and common log…
An engineering guide to LED driver operation, constant-current and constant-voltage outputs, linear and switching topologies, dimming, IC selection, calculations, replacement compatibility, and fault c…
Operational amplifier guide covering op amp basics, feedback, ideal vs real op amps, common configurations, buffer circuits, offset, bias current, gain-bandwidth, slew rate, rail-to-rail limits and sel…
Jumper cables guide covering safe connection order, red and black clamp placement, final ground connection, cable gauge, length, clamp quality, copper vs CCA cables, jump starter comparison and battery…
LDO regulator guide covering low dropout voltage, power dissipation, thermal design, PSRR, output noise, capacitor stability, adjustable LDO circuits, LDO vs buck converter and datasheet selection chec…
Conditional Access Module guide covering CAM meaning, CI/CI+ interface, smart card authorization, DVB security workflow, TV and set-top box compatibility, internal electronics, ESD protection, connecto…
Guide to electronic component obsolescence covering EOL risk, PCN/PDN notices, last-time buy planning, replacement options, form-fit-function validation, counterfeit risk and BOM lifecycle management.
18650 battery guide covering lithium-ion cell basics, 3.6V/3.7V voltage, 4.2V charging, mAh and Wh capacity, protected cells, chargers, BMS, series-parallel packs, holders, welding and sourcing checks.…
