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Texas Instruments LP3855EMP-ADJ/NOPB
- Part No.:
- LP3855EMP-ADJ/NOPB
- Manufacturer:
- Texas Instruments
- Package:
- TO-261-5, TO-261AB
- Datasheet:
-
LP3855EMP-ADJ/NOPB.pdf
- Description:
- IC REG LIN POS ADJ 1.5A SOT223-5
- Quantity:
- Payment:
- Shipping:
Inventory:455
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Product details
Overview
LP3855EMP-ADJ/NOPB from Texas Instruments is an adjustable ultra-low-dropout linear regulator IC delivering up to 1.5A DC output current with dropout as low as 24 mV at 150 mA and 240 mV at full load. It operates from 2.5V to 7.0V input, features 1.216V precision reference voltage at the ADJ pin, and supports ceramic or tantalum output capacitors for stability in microprocessor power supplies and bus terminators.
For engineers reviewing the LP3855EMP-ADJ/NOPB datasheet, LP3855EMP-ADJ/NOPB pinout, LP3855EMP-ADJ/NOPB application, or LP3855EMP-ADJ/NOPB equivalent, key selection considerations include dropout performance at 1.5A, shutdown quiescent current (10 nA), ground pin current behavior across load, PSRR at 120 Hz (73 dB), and compatibility with ceramic output caps up to 150 µF when paired with 10 µF ceramic input capacitance.
Technical Context
The LP3855EMP-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 1.216V bandgap reference at the ADJ pin and requires external R1/R2 resistors to set VOUT = 1.216 × (1 + R1/R2).
It integrates overtemperature and overcurrent protection, delivers fast transient response due to high loop bandwidth, and includes a dedicated SD pin with 1.3V typical shutdown threshold. The device supports stable operation with output capacitors as low as 10 µF (tantalum) or up to 150 µF (ceramic), contingent on input capacitor selection and load current.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Output Current | 1.5A 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 @ 1.5A - enables regulation from 2.5V input down to ~2.26V output, critical for low-voltage logic rails. |
| Reference Voltage | 1.216V (typ) at ADJ pin - sets output accuracy baseline; combined with 1% R1/R2 yields ~1.4% total VOUT error. |
| PSRR | 73 dB @ 120 Hz, VIN = VOUT + 1V - suppresses ripple from upstream switching supplies feeding sensitive analog/digital circuitry. |
| Shutdown IQ | 10 nA (typ) - enables battery-backed systems to maintain >10-year shelf life with regulator disabled. |
| Operating Temp | −40°C to +125°C junction - qualified for automotive under-hood and industrial embedded environments. |
| Noise (RMS) | 150 µV (10 Hz–100 kHz, VOUT = 2.5V) - low enough for powering ADC references and RF bias rails without added filtering. |
Pinout & Package
LP3855EMP-ADJ/NOPB is packaged in the SOT-223-5 surface-mount package (Package Number NDC0005A), featuring exposed thermal pad for enhanced heat dissipation in high-current applications.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 - SD | Shutdown control input | CMOS-compatible active-low enable; pulls regulator into 10 nA shutdown state when ≤0.3V; requires 10 kΩ pull-up if driven by open-drain source. |
| 2 - VIN | Main input supply | Accepts 2.5V–7.0V; must be bypassed with ≥10 µF ceramic/tantalum capacitor placed within 1 cm of pin to ensure stability and transient response. |
| 3 - VOUT | Regulated output | Delivers adjustable voltage (≥1.216V); connects directly to load and output capacitor; trace must be Kelvin-connected to avoid ground bounce. |
| 4 - ADJ | Feedback reference node | Senses 1.216V reference; used with R1/R2 divider to program VOUT; input bias current ≤100 nA minimizes resistor-induced error. |
| 5 - GND | Power ground return | Single-point ground connection for VIN, VOUT, and COUT; must not share traces with system ground currents to prevent instability. |
Key Features
| Feature | Design Value |
|---|---|
| Ultra-low dropout | 24 mV @ 150 mA enables 2.5V input to sustain 2.476V output - essential for post-regulation after buck converters. |
| Ceramic capacitor support | Stable with 10–150 µF ceramic COUT when paired with ≥10 µF ceramic CIN - eliminates ESR dependency and reduces board area vs tantalum. |
| Fast transient response | Load step recovery in <10 µs (per Figure 11–15) - maintains voltage integrity during CPU core wake-up or burst-mode memory access. |
| Low ground current | Typically 4 mA @ 1.5A load - improves efficiency vs bipolar LDOs and reduces PCB heating in dense layouts. |
| Integrated protection | Thermal shutdown + current limiting (3.2A short-circuit limit) - prevents damage during fault conditions without external circuitry. |
Applications
| Microprocessor Core Power | GTL+/SSTL Bus Termination |
|---|---|
|
Use Scenario: Supplying 1.8V/2.5V core voltage to ARM Cortex-M or Intel Atom processors during dynamic frequency scaling. IC Role / Device Role / Timing Role: Primary post-regulator delivering clean, low-noise DC from intermediate 3.3V rail; responds to 1A load transients in <10 µs. Use Value: Maintains VDD within ±1.5% during 100 ns load steps, preventing timing violations or reset events in high-speed logic. |
Use Scenario: Providing termination voltage (VTT) for DDR2/DDR3 memory buses operating at 1.25V or 1.5V. IC Role / Device Role / Timing Role: Low-impedance, fast-settling VTT source tracking half-VDDQ; sinks/sources bidirectional current during data strobes. Use Value: 240 mV dropout at 1.5A allows use of 2.5V input to generate 2.26V VTT, reducing power loss by 37% vs standard LDOs. |
| DSP Power Management | Battery-Powered Instrumentation |
|
Use Scenario: Powering TI C6000 DSPs requiring 1.2V/1.4V core and 3.3V I/O rails with tight noise budgets. IC Role / Device Role / Timing Role: Low-noise (150 µV RMS) core supply decoupled from noisy I/O domain; enabled via processor GPIO. Use Value: Enables 16-bit ADC SNR > 92 dB by suppressing broadband noise that would otherwise alias into conversion band. |
Use Scenario: Regulating 3.3V from single Li-ion cell (2.7–4.2V) in portable gas analyzers with 10-year battery life target. IC Role / Device Role / Timing Role: Main system regulator with shutdown mode activated between sensor readings to minimize average current. Use Value: 10 nA shutdown IQ extends battery runtime by >30% vs alternatives, while 24 mV dropout maximizes usable cell voltage range. |
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 | Lower noise (4.7 µV RMS), higher PSRR (70 dB @ 1 MHz), but 1A max output and higher dropout (120 mV @ 1A). | Better suited for ultra-low-noise analog signal chains; less ideal for 1.5A digital loads or battery-powered systems needing extended voltage range. | Select when noise <5 µV RMS is mandatory and load current ≤1A; avoid when >1.2A sustained current or sub-2.5V input is required. |
| MCP1826T-ADJ/DC | Same 1.5A rating and SOT-223 package, but higher dropout (350 mV @ 1.5A) and no shutdown pin. | Lacks enable/shutdown control and exhibits slower transient response; suitable only for cost-sensitive, non-battery applications. | Choose for fixed-cost BOMs where shutdown and ultra-low dropout are non-critical; verify thermal margin with θJA = 120°C/W. |
Compared with TPS7A4700RGWR and MCP1826T-ADJ/DC, LP3855EMP-ADJ/NOPB uniquely balances 1.5A capability, 24 mV dropout, 10 nA shutdown, and ceramic capacitor compatibility - making it optimal for space-constrained, battery-aware digital systems requiring both high current and wide input range.
Availability
LP3855EMP-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, long-lifecycle assurance, and consistent parametric performance across production batches.
Supply support for LP3855EMP-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 connectivity technologies, with decades of expertise in power management IC design and manufacturing.
The LP3855EMP-ADJ/NOPB belongs to TI's ultra-low-dropout linear regulator family, engineered specifically for high-current, low-voltage digital systems where efficiency, noise, and transient response are critical - including microprocessor cores, memory interfaces, and portable instrumentation.
FAQ
What is the minimum input voltage required for LP3855EMP-ADJ/NOPB to regulate a 1.8V output?
The minimum input voltage equals VOUT + dropout voltage. For 1.8V output at 1.5A load, dropout is 240 mV per datasheet, so minimum VIN = 2.04V. However, the absolute minimum operating VIN is specified as 2.5V - therefore LP3855EMP-ADJ/NOPB requires ≥2.5V input regardless of output setting. This ensures internal circuitry functions correctly across temperature and process variation.
Can LP3855EMP-ADJ/NOPB safely drive a 150 µF ceramic output capacitor?
Yes - LP3855EMP-ADJ/NOPB supports up to 150 µF ceramic COUT when paired with ≥10 µF ceramic CIN and operating at ≤1.5A load, as confirmed in Figure 19 of the SNVS244F datasheet. Exceeding this value risks instability; always verify phase margin in final layout using recommended test conditions (CIN = COUT = 10 µF ceramic, TJ = 25°C).
How does the ADJ pin bias current affect output voltage accuracy in LP3855EMP-ADJ/NOPB?
LP3855EMP-ADJ/NOPB ADJ pin bias current is ≤100 nA. When using R1 = 100 kΩ and R2 = 10 kΩ to set 1.216V × (1 + 10) = 13.376V, the error introduced is <0.1% - negligible for most designs. But if R1 exceeds 1 MΩ, bias current flow through R1 adds measurable offset; keep R1 ≤500 kΩ for <0.5% added error.
Is a feed-forward capacitor (CFF) required for stable operation of LP3855EMP-ADJ/NOPB?
Yes - CFF is mandatory for loop compensation. Per Application Hints, it must be selected so the zero frequency Fz = 1/(2π × R1 × CFF) ≈ 45 kHz. For R1 = 100 kΩ, CFF = 35 pF (X5R/X7R ceramic). Omitting CFF degrades phase margin and may cause oscillation under light loads or fast transients.
Does LP3855EMP-ADJ/NOPB have reverse current protection?
No - LP3855EMP-ADJ/NOPB contains a parasitic body diode between VIN and VOUT. If VOUT is forced above VIN (e.g., during hot-swap or backup supply activation), forward current flows from VOUT to VIN. The diode tolerates 200 mA continuous and 1 A peak; external reverse-blocking MOSFET or diode is required for full protection.
LP3855EMP-ADJ/NOPB Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- -
- Package/Case:
- TO-261-5, TO-261AB
- 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:
- SOT-223-5
LP3855EMP-ADJ/NOPB FAQ
1.How can I place an order for LP3855EMP-ADJ/NOPB through Aetrix?
Please submit a Request for Quotation (RFQ) for LP3855EMP-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 LP3855EMP-ADJ/NOPB reliable?
The price and inventory of LP3855EMP-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 LP3855EMP-ADJ/NOPB is usually 5 days.
3.What payment methods are accepted for LP3855EMP-ADJ/NOPB?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LP3855EMP-ADJ/NOPB transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LP3855EMP-ADJ/NOPB?
LP3855EMP-ADJ/NOPB orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LP3855EMP-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 LP3855EMP-ADJ/NOPB?
For technical support, including LP3855EMP-ADJ/NOPB datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LP3855EMP-ADJ/NOPB requirements.
6.How does Aetrix verify that LP3855EMP-ADJ/NOPB is sourced from the original manufacturer or authorized distributors?
All LP3855EMP-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 LP3855EMP-ADJ/NOPB meets industry standards.
7.What is the process for return or replacement of LP3855EMP-ADJ/NOPB?
All LP3855EMP-ADJ/NOPB units undergo pre-shipment inspection (PSI). If there is an issue with LP3855EMP-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 LP3855EMP-ADJ/NOPB part is unused and in its original packaging.
Return procedure for LP3855EMP-ADJ/NOPB:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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