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Texas Instruments LP3855ESX-ADJ/NOPB
- Part No.:
- LP3855ESX-ADJ/NOPB
- Manufacturer:
- Texas Instruments
- Package:
- TO-263-6, D2PAK (5 Leads + Tab), TO-263BA
- Datasheet:
-
LP3855ESX-ADJ/NOPB.pdf
- Description:
- IC REG LINEAR POS ADJ 1.5A DDPAK
- Quantity:
- Payment:
- Shipping:
Inventory:267
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Product details
Overview
LP3855ESX-ADJ/NOPB from Texas Instruments is an adjustable ultra-low-dropout linear regulator delivering up to 1.5A DC output current with dropout as low as 24 mV at 150 mA and 240 mV at 1.5 A. It operates from 2.5 V to 7.0 V input, features 1.216 V internal reference, and supports ceramic or tantalum output capacitors for microprocessor power supplies and bus terminators.
For engineers reviewing the LP3855ESX-ADJ/NOPB datasheet, LP3855ESX-ADJ/NOPB pinout, LP3855ESX-ADJ/NOPB application, or LP3855ESX-ADJ/NOPB equivalent, key selection criteria include dropout voltage under full load, shutdown quiescent current (10 nA), ground pin current stability (4 mA typical at 1.5 A), PSRR (73 dB at 120 Hz), and compatibility with ceramic output caps up to 150 µF when paired with 10 µF ceramic input capacitance.
Technical Context
The LP3855ESX-ADJ/NOPB uses a PMOS pass element fabricated on a CMOS process, enabling low quiescent current independent of load and operation under ultra-low dropout conditions. Its feedback loop relies on a precision 1.216 V bandgap reference at the ADJ pin and requires external R1/R2 resistors to set output voltage per VOUT = 1.216 × (1 + R1/R2).
It integrates overtemperature and overcurrent protection, delivers fast load transient response due to high loop bandwidth, and includes a dedicated shutdown (SD) pin with 1.3 V threshold and 20 µs turn-off delay. Stability is ensured with ≥10 µF output capacitance and optional feed-forward capacitor CFF for phase lead compensation.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Output Current | 1.5 A DC maximum - supports high-current digital loads like microprocessors and GTL+ bus terminators without derating at TJ ≤ 125°C. |
| Dropout Voltage | 24 mV @ 150 mA / 240 mV @ 1.5 A - enables regulation from 2.5 V input down to ~2.26 V output, critical for low-voltage logic rails. |
| Reference Voltage | 1.216 V (±1.4% with 1% resistors) - sets output via external divider; ADJ pin bias current ≤100 nA minimizes divider error. |
| PSRR | 73 dB @ 120 Hz - suppresses ripple from upstream switching regulators, reducing need for additional filtering in hybrid power architectures. |
| Shutdown IQ | 10 nA typical - allows battery-powered systems to achieve multi-year shelf life when regulator is disabled. |
| Ground Pin Current | 4 mA @ 1.5 A load - remains stable across temperature; enables accurate power loss calculation: PD = (VIN−VOUT)×IOUT + VIN×IGND. |
| Operating Temp | −40°C to +125°C junction - qualified for industrial and automotive under-hood applications without derating. |
Pinout & Package
LP3855ESX-ADJ/NOPB is packaged in DDPAK/TO-263-5 (Package Number NDH0005D), featuring exposed thermal pad for PCB heat sinking. Pin 1 (SD) enables logic-level shutdown; Pin 2 (VIN) accepts 2.5–7.0 V input; Pin 3 (GND) is power ground; Pin 4 (VOUT) delivers regulated output; Pin 5 (ADJ) connects to resistor divider for output programming.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 - SD | Shutdown control input | CMOS-compatible input; pulls regulator into 10 nA shutdown when ≤0.3 V; requires 10 kΩ pull-up if driven by open-drain source. |
| 2 - VIN | Main power input | Accepts 2.5–7.0 V supply; must be bypassed with ≥10 µF ceramic/tantalum capacitor placed within 1 cm of pin. |
| 3 - GND | Power ground reference | Single-point Kelvin connection required for stability; ties regulator die, CIN, and COUT grounds together to avoid ground-loop oscillation. |
| 4 - VOUT | Regulated output | Delivers adjustable voltage (≥1.216 V); requires ≥10 µF output capacitor with ESR between 0.01–1 Ω for stability; supports ceramic caps up to 150 µF with proper CIN. |
| 5 - ADJ | Feedback reference node | Connects to R1–R2 divider midpoint; 1.216 V reference enables precise output setting; ADJ bias current ≤100 nA limits resistor value selection. |
Key Features
| Feature | Design Value |
|---|---|
| Ultra-low dropout | 24 mV @ 150 mA enables 2.5 V input to sustain 2.476 V output - critical for post-regulation of buck converter outputs. |
| Ceramic capacitor support | Stable with ≥10 µF ceramic output cap when paired with ≥10 µF ceramic input cap - eliminates tantalum cost/supply risk and improves high-frequency bypassing. |
| Fast transient response | Load step recovery in <10 µs (typical) - maintains voltage within ±1% during 1 A load transients, protecting sensitive logic cores. |
| Integrated protection | Thermal shutdown and foldback current limiting activate before junction exceeds 165°C or output shorts - prevents catastrophic failure without external circuitry. |
| Low-noise operation | 150 µVrms (10 Hz–100 kHz) - suitable for analog subsystems (e.g., ADC references) without requiring additional LDO filtering stages. |
Applications
| Microprocessor Core Supply | GTL+/SSTL Bus Termination |
|---|---|
|
Use Scenario: Powering 1.2–1.8 V core rails of ARM Cortex-A series or Intel Atom processors in embedded computing modules. IC Role / Device Role / Timing Role: Primary post-regulator converting 3.3 V or 5 V intermediate rail to precise, low-noise core voltage with fast transient response. Use Value: 240 mV dropout at 1.5 A allows >90% efficiency at 1.2 V output from 3.3 V input; 150 µVrms noise avoids timing jitter in high-speed clock domains. |
Use Scenario: Providing termination voltage (typically 1.2 V or 1.5 V) for GTL+, SSTL_2, or SSTL_18 memory buses in server DIMMs and FPGA mezzanine cards. IC Role / Device Role / Timing Role: Low-impedance, low-noise voltage source matching bus VTT requirements with minimal voltage drift under dynamic load. Use Value: 0.06% load regulation ensures <±0.9 mV shift across 0–1.5 A load range; fast transient response prevents signal integrity violations during burst-mode data transfers. |
| DSP Power Management | Battery-Powered Instrumentation |
|
Use Scenario: Supplying 1.8 V or 2.5 V I/O and core rails for TI C6000 or Analog Devices SHARC DSPs in real-time audio processing units. IC Role / Device Role / Timing Role: Dual-rail regulator (using two LP3855ESX-ADJ/NOPB) delivering isolated, low-noise power to analog and digital sections. Use Value: 10 nA shutdown current enables deep-sleep modes; 73 dB PSRR rejects switching noise from shared DC/DC converters feeding multiple rails. |
Use Scenario: Regulating lithium-ion battery (3.0–4.2 V) output to stable 3.3 V for portable oscilloscopes, multimeters, or gas sensors with 10+ year field life. IC Role / Device Role / Timing Role: Primary system regulator enabling long-term operation with minimal self-discharge during storage or standby. Use Value: 10 nA shutdown IQ extends battery shelf life beyond 15 years; −40°C to +125°C rating supports operation in unheated outdoor enclosures. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar adjustable LDO regulator applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| TPS7A4700RGWR | 20 V max input, 1 A output, 4 µVrms noise, 500 µA quiescent current - lower noise but higher IQ and lower current. | Better for ultra-low-noise analog front-ends (e.g., precision ADCs); unsuitable for >1 A digital loads. | Select TPS7A4700RGWR only when noise <5 µVrms is mandatory and load current ≤1 A. |
| MCP1826T-ADJ/DC | 3 A output, 350 mV dropout @ 3 A, 90 µA quiescent current, SOT-223 package - higher current but higher dropout and IQ. | Suitable for cost-sensitive 3 A applications where 240 mV dropout is not required; lacks ceramic-cap stability guarantees. | Choose MCP1826T-ADJ/DC only when output current >1.5 A is needed and ceramic capacitor compatibility is secondary. |
Compared with TPS7A4700RGWR and MCP1826T-ADJ/DC, LP3855ESX-ADJ/NOPB uniquely balances 1.5 A capability, 240 mV dropout, 10 nA shutdown, and guaranteed ceramic capacitor stability - making it optimal for space-constrained, battery-aware digital systems requiring both performance and longevity.
Availability
LP3855ESX-ADJ/NOPB is available at Aetrix Electronics and suitable for microprocessor power supplies, GTL+/SSTL bus terminators, and DSP power management requiring stable component supply across industrial temperature ranges and long production lifecycles.
Supply support for LP3855ESX-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 LDO design heritage and broad automotive/industrial qualification.
The LP3855ESX-ADJ/NOPB belongs to TI's ultra-low-dropout linear regulator family, engineered specifically for high-current, low-voltage digital systems where efficiency, transient response, and shutdown leakage are critical - including microprocessor cores, memory interfaces, and portable instrumentation.
FAQ
What is the minimum input voltage required for LP3855ESX-ADJ/NOPB to regulate a 1.5 V output?
The minimum input voltage equals the sum of the desired output voltage and the dropout voltage at the operating load. For LP3855ESX-ADJ/NOPB delivering 1.5 V at 1.5 A, dropout is 240 mV, so minimum VIN = 1.5 V + 0.24 V = 1.74 V. However, the absolute minimum specified operating VIN is 2.5 V per datasheet - thus 2.5 V is the practical lower limit regardless of calculated dropout.
Can LP3855ESX-ADJ/NOPB use only ceramic capacitors for both input and output?
Yes - LP3855ESX-ADJ/NOPB is explicitly characterized for stability with ceramic input and output capacitors. With 10 µF ceramic CIN, it supports ceramic COUT up to 150 µF at 1.5 A load. X5R or X7R dielectrics are required; Z5U/Y5V types are prohibited due to severe capacitance loss with voltage and temperature.
What is the purpose of the CFF feed-forward capacitor in LP3855ESX-ADJ/NOPB circuits?
CFF adds phase lead to improve loop stability and transient response. Its value is selected so the zero frequency Fz = 1/(2π × R1 × CFF) ≈ 45 kHz. For example, if R1 = 100 kΩ, CFF ≈ 33 pF. CFF must be a high-quality ceramic (X5R/X7R) placed close to the ADJ and VOUT pins per TI layout guidelines.
Does LP3855ESX-ADJ/NOPB require a pull-up resistor on the SD pin?
Yes - unless driven by a rail-to-rail CMOS output that actively pulls high and low, LP3855ESX-ADJ/NOPB requires a 10 kΩ pull-up resistor from SD to VIN. This ensures reliable startup and prevents floating-input-induced erratic shutdown behavior. If unused, SD must be tied directly to VIN.
How does reverse current flow affect LP3855ESX-ADJ/NOPB when VOUT > VIN?
LP3855ESX-ADJ/NOPB contains a parasitic body diode between VIN and VOUT. If VOUT exceeds VIN, this diode becomes forward-biased, allowing reverse current. The device tolerates up to 200 mA continuous or 1 A peak reverse current - sufficient for most back-powering scenarios but requires external current limiting if sustained reverse flow is expected.
LP3855ESX-ADJ/NOPB Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- -
- Package/Case:
- TO-263-6, D2PAK (5 Leads + Tab), TO-263BA
- Packaging:
- Tape & Reel (TR)
- Product Status:
- Active
- Output Configuration:
- Positive
- Output Type:
- Adjustable
- Number of Regulators:
- 1
- Voltage - Input (Max):
- 7V
- Voltage - Output (Min/Fixed):
- 1.23V
- Voltage - Output (Max):
- 6.6V
- Voltage Dropout (Max):
- 0.435V @ 1.5A
- Current - Output:
- 1.5A
- Current - Quiescent (Iq):
- 3 mA
- Current - Supply (Max):
- 10 mA
- PSRR:
- 73dB ~ 57dB (120Hz)
- Control Features:
- Enable
- Protection Features:
- Over Current, Over Temperature, Short Circuit
- Operating Temperature:
- -40°C ~ 125°C
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- TO-263 (DDPAK-5)
LP3855ESX-ADJ/NOPB FAQ
1.How can I place an order for LP3855ESX-ADJ/NOPB through Aetrix?
Please submit a Request for Quotation (RFQ) for LP3855ESX-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 LP3855ESX-ADJ/NOPB reliable?
The price and inventory of LP3855ESX-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 LP3855ESX-ADJ/NOPB is usually 5 days.
3.What payment methods are accepted for LP3855ESX-ADJ/NOPB?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LP3855ESX-ADJ/NOPB transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LP3855ESX-ADJ/NOPB?
LP3855ESX-ADJ/NOPB orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LP3855ESX-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 LP3855ESX-ADJ/NOPB?
For technical support, including LP3855ESX-ADJ/NOPB datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LP3855ESX-ADJ/NOPB requirements.
6.How does Aetrix verify that LP3855ESX-ADJ/NOPB is sourced from the original manufacturer or authorized distributors?
All LP3855ESX-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 LP3855ESX-ADJ/NOPB meets industry standards.
7.What is the process for return or replacement of LP3855ESX-ADJ/NOPB?
All LP3855ESX-ADJ/NOPB units undergo pre-shipment inspection (PSI). If there is an issue with LP3855ESX-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 LP3855ESX-ADJ/NOPB part is unused and in its original packaging.
Return procedure for LP3855ESX-ADJ/NOPB:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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