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Texas Instruments LM1085ISX-ADJ/NOPB
- Part No.:
- LM1085ISX-ADJ/NOPB
- Manufacturer:
- Texas Instruments
- Package:
- TO-263-4, D2PAK (3 Leads + Tab), TO-263AA
- Datasheet:
-
LM1085ISX-ADJ/NOPB.pdf
- Description:
- IC REG LIN POS ADJ 3A DDPAK
- Quantity:
- Payment:
- Shipping:
Inventory:1,780
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Product details
Overview
LM1085ISX-ADJ/NOPB from Texas Instruments is a 3-A adjustable-output positive low-dropout linear regulator in DDPAK/TO-263 package, featuring 1.5 V maximum dropout at full load, 1.25 V internal reference voltage, and integrated thermal shutdown and current limiting. It serves as a post-regulator for switching supplies and local power rail stabilization in microprocessor and battery-charger systems.
For engineers reviewing the LM1085ISX-ADJ/NOPB datasheet, LM1085ISX-ADJ/NOPB pinout, LM1085ISX-ADJ/NOPB application, or LM1085ISX-ADJ/NOPB equivalent, key selection criteria include dropout voltage at 3 A, adjust-pin current (≤120 µA), ripple rejection (75 dB typical), and thermal performance in high-power-density PCB layouts.
Technical Context
The LM1085ISX-ADJ/NOPB uses a single-NPN quasi-LDO pass transistor architecture-distinct from Darlington-based regulators like the LM317-enabling lower dropout and inherently lower quiescent current. Its feedback loop relies on a zener-trimmed bandgap reference with 1.25 V nominal output-to-adjust voltage.
Output voltage is set externally via two resistors (R1 between OUT–ADJ, R2 between ADJ–GND), where VOUT = 1.25 V × (1 + R2/R1) + IADJ × R2. Adjust-pin current variation (≤5 µA over temperature and line conditions) directly impacts output accuracy in precision applications.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Output Current | 3 A continuous - supports high-current rails for FPGAs, DSPs, and motor drivers without external pass devices. |
| Dropout Voltage | 1.5 V max at 3 A - enables regulation from 4.75 V input to 3.3 V output, critical for battery-powered systems near end-of-discharge. |
| Reference Voltage | 1.250 V ±1% - forms the precision basis for programmable output; sets minimum VOUT = 1.2 V with R2 = 0 Ω. |
| Ripple Rejection | 75 dB typical at 120 Hz - suppresses switching noise from upstream DC/DC converters, reducing need for additional filtering stages. |
| Line Regulation | 0.015% typical - ensures <±0.5 mV output shift per 1 V input change, vital for stable analog sensor biasing. |
| Load Regulation | 0.1% typical - guarantees ≤3 mV output deviation from no-load to full 3 A, supporting dynamic digital loads. |
| Quiescent Current | 5–10 mA - remains constant across input voltage and load, simplifying standby power budgeting. |
| Thermal Shutdown | Activates at TJ ≥150°C - protects against sustained overload or inadequate heatsinking in enclosed industrial enclosures. |
Pinout & Package
LM1085ISX-ADJ/NOPB is housed in a thermally enhanced DDPAK/TO-263 (KTT) package measuring 10.18 mm × 8.41 mm, with exposed thermal pad soldered to PCB copper for optimal heat transfer. The 3-pin configuration supports compact layout and high-power dissipation up to 30 W with proper board-level thermal design.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| ADJ | Adjust reference node | Sinks ≤120 µA; connects to resistor divider to set VOUT; bypass capacitor here improves ripple rejection. |
| OUTPUT | Regulated output node | Delivers up to 3 A; requires ≥10 µF tantalum or ≥50 µF aluminum output capacitance for stability. |
| INPUT | Unregulated input node | Accepts up to 29 V differential vs. OUTPUT; internal diode withstands 10–20 A transient surge during input short. |
Key Features
| Feature | Design Value |
|---|---|
| Quasi-LDO NPN Pass Transistor | Enables 1.5 V dropout while maintaining 5–10 mA quiescent current-lower than PNP LDOs with comparable current rating. |
| Integrated Thermal Protection | Shuts down at 150°C junction temperature and auto-recovers when cooled-eliminates need for external thermal monitoring circuitry. |
| Adjust-Pin Bypass Capability | Adding CADJ (e.g., 10 µF) between ADJ and GND restores ripple rejection degraded by output voltage gain, enabling clean 12 V or 15 V rails. |
| Stable with Low-ESR Capacitors | Works reliably with ceramic, tantalum, or aluminum electrolytic outputs-no series resistor required, unlike older regulators. |
| Robust Short-Circuit Recovery | Current limit adapts to VIN–VOUT differential; recovers automatically after overload removal without power cycling in most cases. |
Applications
| Battery Charger | Microprocessor Supply |
|---|---|
Use Scenario: Constant-current/constant-voltage charging of 12 V sealed lead-acid or LiFePO₄ battery banks from unregulated DC sources. IC Role / Device Role / Timing Role: Adjustable linear regulator configured as precision current source using sense-resistor feedback on ADJ pin. Use Value: Delivers stable 3 A charge current with <±1% accuracy and thermal foldback protection during extended float stage. | Use Scenario: Local point-of-load regulation for FPGA core voltage (e.g., 1.2 V) or I/O bank (e.g., 3.3 V) on dense PCBs. IC Role / Device Role / Timing Role: Post-regulator cleaning ripple from switching DC/DC converter outputs; provides low-noise, fast-transient response supply. Use Value: Maintains <±3 mV load regulation across 0–3 A steps, minimizing logic timing jitter and ADC reference error. |
| Post Regulation for Switching Supplies | High-Efficiency Linear Regulator |
Use Scenario: Final-stage regulation after 24 V → 5 V buck converter to power analog front-ends or RF modules requiring ultra-low noise. IC Role / Device Role / Timing Role: Low-dropout buffer suppressing switching artifacts; operates with only 0.5 V headroom (e.g., 5.5 V input → 5.0 V output). Use Value: Achieves 75 dB ripple rejection at 100 kHz, reducing conducted EMI and eliminating need for ferrite-bead filters. | Use Scenario: Primary 3.3 V or 5 V rail in industrial controllers where simplicity, reliability, and no switching noise outweigh efficiency concerns. IC Role / Device Role / Timing Role: Standalone linear regulator replacing multi-component discrete designs; pin-compatible with LM317 footprint. Use Value: Reduces BOM count to two resistors and one capacitor while delivering full 3 A with built-in fault protection. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar adjustable positive linear regulator applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LM1085IT-ADJ/NOPB | TO-220 package (14.99 mm × 10.16 mm); higher RθJA (40.6°C/W vs. 22.8°C/W); same electrical specs. | Lower power density; suited for prototyping or low-volume assemblies with through-hole assembly. | Select when manual heatsink mounting or legacy TO-220 footprint compatibility is required. |
| LT1086CM-ADJ#PBF | 3 A rating; 1.3 V dropout typ.; higher cost; tighter reference tolerance (1.25 V ±0.5%); lower IADJ (50 µA max). | Better accuracy and lower dropout for precision instrumentation; limited automotive qualification. | Choose when <±0.5% output accuracy or sub-1.4 V dropout at 3 A is mandatory, and budget allows premium pricing. |
Compared with LM1085IT-ADJ/NOPB, LM1085ISX-ADJ/NOPB delivers 44% lower junction-to-ambient thermal resistance for equivalent PCB copper area, enabling 30% higher continuous power in space-constrained designs; versus LT1086CM-ADJ#PBF, it trades tighter reference tolerance for broader temperature range support (−40°C to +125°C) and TI's long-term product continuity assurance.
Availability
LM1085ISX-ADJ/NOPB is available at Aetrix Electronics and suitable for industrial control systems, battery-powered test equipment, and embedded computing platforms requiring stable component supply, long-lifecycle availability, and RoHS-compliant packaging.
Supply support for LM1085ISX-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 ICs and broad industrial market support.
The LM1085 product line was designed for high-current, low-noise linear regulation in demanding environments-targeting applications where switching noise, transient response, and thermal robustness outweigh raw efficiency requirements.
FAQ
What is the maximum input-to-output voltage differential for LM1085ISX-ADJ/NOPB?
The absolute maximum input-to-output voltage differential for LM1085ISX-ADJ/NOPB is 29 V, as specified in the Absolute Maximum Ratings table. This rating applies across the full operating temperature range and defines the upper limit before potential device damage occurs. Exceeding this value-even briefly-may cause permanent failure. Designers must ensure that transient conditions, such as input surges or load-dump events, remain within this margin. The LM1085ISX-ADJ/NOPB datasheet confirms this value under Section 6.1, and it is independent of output voltage setting or load current.
Can LM1085ISX-ADJ/NOPB be used as a constant-current source?
Yes, LM1085ISX-ADJ/NOPB can be configured as a precision constant-current source by connecting a sense resistor between the ADJ pin and ground, with the load returned to the OUTPUT pin. In this topology, the regulator maintains 1.25 V across the sense resistor, delivering IOUT = 1.25 V / RSENSE. For example, a 0.417 Ω resistor yields 3 A. The LM1085ISX-ADJ/NOPB's low adjust-pin current drift (<5 µA) and tight reference tolerance ensure <±1% current accuracy across temperature. This mode is explicitly validated in TI's Application Note SNVS038H, Figure 18 (Battery Charger).
What output capacitors ensure stability for LM1085ISX-ADJ/NOPB?
LM1085ISX-ADJ/NOPB requires ≥10 µF tantalum or ≥50 µF aluminum electrolytic output capacitance for guaranteed stability across all operating conditions. Solid tantalum capacitors are preferred due to their stable ESR over temperature (typically 0.5–1.5 Ω), which provides the necessary phase margin zero in the feedback loop. Ceramic capacitors alone are insufficient unless paired with a series resistor (~1 Ω) to emulate ESR. The LM1085ISX-ADJ/NOPB datasheet specifies these values in Section 7.4.2 and validates them in Figure 13's stability analysis.
Does LM1085ISX-ADJ/NOPB require an input capacitor?
Yes, LM1085ISX-ADJ/NOPB recommends a 10 µF input capacitor-typically aluminum or tantalum-placed close to the INPUT and GND pins. This capacitor reduces high-frequency noise from upstream sources and prevents instability caused by source impedance interacting with the regulator's internal compensation. While not strictly mandatory for basic functionality, omission risks oscillation under dynamic load or poor line transient response. TI's LM1085ISX-ADJ/NOPB datasheet states this in Section 7.4.2 and illustrates it in all application schematics (e.g., Figure 15).
How does the adjust-pin current affect output voltage accuracy in LM1085ISX-ADJ/NOPB?
The adjust-pin current (IADJ) of LM1085ISX-ADJ/NOPB-up to 120 µA maximum-flows through the lower feedback resistor (R2), creating an error term: ΔVOUT = IADJ × R2. For example, with R2 = 1 kΩ, this adds up to 120 mV of offset. To minimize impact, R1 should be kept near 100 Ω (yielding ~10 mA reference current), making IADJ-induced error <1%. The LM1085ISX-ADJ/NOPB datasheet quantifies IADJ variation in Section 6.5 and confirms its bounded behavior across temperature and line conditions.
LM1085ISX-ADJ/NOPB Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- -
- Package/Case:
- TO-263-4, D2PAK (3 Leads + Tab), TO-263AA
- Packaging:
- Tape & Reel (TR)
- Product Status:
- Active
- Output Configuration:
- Positive
- Output Type:
- Adjustable
- Number of Regulators:
- 1
- Voltage - Input (Max):
- 29V
- Voltage - Output (Min/Fixed):
- 1.25V
- Voltage - Output (Max):
- 15V
- Voltage Dropout (Max):
- 1.5V @ 3A
- Current - Output:
- 3A
- Current - Quiescent (Iq):
- 10 mA
- Current - Supply (Max):
- -
- PSRR:
- 75dB (120Hz)
- Control Features:
- -
- Protection Features:
- Over Current, Over Temperature
- Operating Temperature:
- -40°C ~ 125°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- TO-263 (DDPAK-3)
LM1085ISX-ADJ/NOPB FAQ
1.How can I place an order for LM1085ISX-ADJ/NOPB through Aetrix?
Please submit a Request for Quotation (RFQ) for LM1085ISX-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 LM1085ISX-ADJ/NOPB reliable?
The price and inventory of LM1085ISX-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 LM1085ISX-ADJ/NOPB is usually 5 days.
3.What payment methods are accepted for LM1085ISX-ADJ/NOPB?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LM1085ISX-ADJ/NOPB transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LM1085ISX-ADJ/NOPB?
LM1085ISX-ADJ/NOPB orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LM1085ISX-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 LM1085ISX-ADJ/NOPB?
For technical support, including LM1085ISX-ADJ/NOPB datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LM1085ISX-ADJ/NOPB requirements.
6.How does Aetrix verify that LM1085ISX-ADJ/NOPB is sourced from the original manufacturer or authorized distributors?
All LM1085ISX-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 LM1085ISX-ADJ/NOPB meets industry standards.
7.What is the process for return or replacement of LM1085ISX-ADJ/NOPB?
All LM1085ISX-ADJ/NOPB units undergo pre-shipment inspection (PSI). If there is an issue with LM1085ISX-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 LM1085ISX-ADJ/NOPB part is unused and in its original packaging.
Return procedure for LM1085ISX-ADJ/NOPB:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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