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Texas Instruments LM2825N-ADJ
- Part No.:
- LM2825N-ADJ
- Manufacturer:
- Texas Instruments
- Package:
- 24-DIP (0.600", 15.24mm)
- Datasheet:
-
LM2825N-ADJ.pdf
- Description:
- IC REG BUCK ADJ 1A 24PDIP
- Quantity:
- Payment:
- Shipping:
Inventory:2,114
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Product details
Overview
LM2825N-ADJ from Texas Instruments is a self-contained 1A adjustable-output DC-DC buck converter in a 24-pin PDIP package, delivering 1.23V to 8V output with ±4% tolerance, 74% typical efficiency at 12VIN/0.5A, and 65μA standby quiescent current. It integrates all active/passive components for high-efficiency step-down regulation in industrial power supplies and embedded systems requiring stable mid-voltage rails.
For engineers reviewing the LM2825N-ADJ datasheet, LM2825N-ADJ pinout, LM2825N-ADJ application, or LM2825N-ADJ equivalent, key selection criteria include its 4.5–40V input range, programmable output via external resistors, TTL-compatible shutdown/soft-start control, thermal shutdown protection, and compliance with CISPR 22 Class B radiated EMI limits.
Technical Context
The LM2825N-ADJ implements a fixed-frequency (150 kHz) current-mode PWM buck topology with internal power switch, error amplifier, oscillator, and protection circuitry. Its adjustable version uses an internal 1.23V reference connected to the ADJ pin, enabling output programming via resistor divider R1/R2 while maintaining tight line/load regulation (≤8 mV) across temperature.
It features integrated thermal shutdown, cycle-by-cycle current limiting (1.2A min), and programmable soft-start via external capacitor on the SS pin. The device operates over −40°C to +85°C ambient and supports TTL-level shutdown with 1.3V threshold and sub-10μA shutdown current.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Output Voltage Range | 1.23V to 8V - Programmable via external R1/R2; optimized for this range per datasheet Figure 18 and LM2825-ADJ Electrical Characteristics. |
| Max Output Current | 1A - Fully specified at TA = 25°C; derated at temperature extremes and high VIN/VOUT differentials per Figures 20–23. |
| Input Voltage Range | 4.5V to 40V - Minimum ensures proper startup; maximum aligns with absolute max rating of +45V VIN. |
| Efficiency (Typ.) | 74% - Measured at VIN = 12V, ILOAD = 0.5A, VOUT = 3V per LM2825-ADJ Electrical Characteristics table. |
| Quiescent Current | 65 μA - Standby IQ at SD/SS = 0V; enables low-power hold mode in battery-backed or always-on systems. |
| Oscillator Frequency | 150 kHz - Fixed switching frequency; determines external component sizing and EMI profile per All Versions Electrical Characteristics. |
| Output Tolerance | ±4% - Guaranteed over full operating temperature and load range; includes initial accuracy and drift. |
Pinout & Package
Package: 24-pin plastic dual-in-line (PDIP), NFL package drawing, 1.25 × 0.54 × 0.26 inches (31.8 × 13.7 × 6.6 mm), through-hole mounting. Thermal resistance θJA = 30°C/W with 2 in² copper area.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1, 2, 3, 4, 5, 6, 7, 18, 19, 20, 21, 22, 23, 24 | NC (No Connect) | Electrically isolated; connected to copper pads on PCB solely for thermal conduction per Figure 25 layout note. |
| 8, 9 | Internal Ripple Reduction Node | Shorting pins 8 and 9 reduces output ripple by 25–33%; requires feed-forward capacitor CFF (680–2700 pF) for stability per Application Information. |
| 10 | GND | Power and signal ground reference; must be low-impedance connection to minimize noise and ensure regulation accuracy. |
| 11 | VIN | Main input supply (4.5–40V); requires local bypass capacitor if >6″ from main filter per Figure 18 note. |
| 12 | VOUT | Regulated output; delivers up to 1A with programmable voltage set by R1/R2 network on ADJ pin. |
| 13 | ADJ | Feedback input; senses output via resistor divider; bias current ≤100 nA ensures minimal loading error. |
| 14 | SD/SS | Combined shutdown/soft-start control; <1.3V = shutdown (65 μA IQ), >2.0V = soft-start enabled (1.6 μA ISS). |
| 15, 16, 17 | SW | Switch node; connects internal power MOSFET drain to external inductor; high dV/dt requires careful layout. |
Key Features
| Feature | Design Value |
|---|---|
| Integrated Buck Converter | Contains internal power switch, controller, oscillator, and protection-no external MOSFET or driver required. |
| Programmable Output | 1.23V to 8V range with ±4% tolerance; uses precision 1.23V internal reference and low-bias ADJ pin (≤100 nA). |
| TTL-Compatible Control | SD/SS pin accepts standard logic levels: <0.6V = shutdown, >2.0V = soft-start; enables direct MCU GPIO interfacing. |
| Radiated EMI Compliance | Meets CISPR 22 Class B limits at 10 m distance (30 dBμV/m @ 30–230 MHz), verified per datasheet EMI test data. |
| Thermal & Overcurrent Protection | Auto-recovering thermal shutdown and cycle-by-cycle current limit (1.2A min) prevent damage under fault conditions. |
Applications
| Industrial Power Supply | Embedded System Rail Generator |
|---|---|
Use Scenario: Generating a stable 5V or 3.3V intermediate rail from a 24V factory bus in PLC I/O modules or sensor transmitters. IC Role / Device Role / Timing Role: Primary buck regulator providing regulated DC power to microcontrollers, ADCs, and communication interfaces. Use Value: Eliminates need for external FET, gate driver, and compensation network-reducing BOM count and layout complexity while meeting industrial temp range (−40°C to +85°C). | Use Scenario: Powering FPGA core or SoC auxiliary rails in field-deployable edge computing devices with limited board space. IC Role / Device Role / Timing Role: Adjustable-output DC-DC converter configured for 1.8V or 2.5V using precision R1/R2 feedback. Use Value: Enables single-part flexibility across multiple voltage requirements; ±4% output tolerance ensures reliable logic-level operation without post-regulation. |
| Distributed Power Architecture | Pre-Regulator for Linear Regulators |
Use Scenario: Local point-of-load conversion in telecom shelf systems where 48V backplane feeds multiple 12V/5V subsystems. IC Role / Device Role / Timing Role: High-efficiency pre-regulator stepping down 48V to 12V before LDOs, reducing heat dissipation vs. direct linear regulation. Use Value: 74% typical efficiency at 12VOUT cuts power loss by >50% compared to linear solution; wide 4.5–40V input accommodates brownout margins. | Use Scenario: Reducing 12V supply to 3.3V for analog front-end circuits requiring ultra-low noise, such as precision instrumentation amplifiers. IC Role / Device Role / Timing Role: Efficient pre-regulator feeding low-noise LDO, minimizing thermal stress on downstream linear regulator. Use Value: Low 65μA standby IQ preserves system sleep mode integrity; programmable soft-start prevents inrush into sensitive analog stages. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar adjustable-output buck regulator applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LM2576HVS-ADJ | Higher 60V max input, 3A output, 52 kHz switching frequency; larger TO-220 package; no integrated soft-start. | Better suited for high-input-voltage industrial or automotive applications requiring >1A load current. | Select when input exceeds 40V or continuous load >1A is needed; requires external soft-start circuitry. |
| TPS54202DDCR | 2A synchronous buck, 4.5–28V input, 500 kHz switching, 2.5μA IQ in Eco-mode; SOT-23-6 package. | Targets space-constrained, battery-powered designs needing higher efficiency and lower quiescent current. | Choose for compact PCBs and ultra-low-power operation; lacks integrated EMI filtering and PDIP thermal mass. |
Compared with LM2825N-ADJ, LM2576HVS-ADJ offers higher voltage/current headroom but requires more external components and lacks integrated soft-start, while TPS54202DDCR delivers superior efficiency and miniaturization at the cost of reduced thermal robustness and EMI performance in noisy environments.
Availability
LM2825N-ADJ is available at Aetrix Electronics and suitable for industrial power supplies, embedded system rail generation, distributed power architectures, and pre-regulator applications requiring stable component supply and long-term design continuity.
Supply support for LM2825N-ADJ 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 conversion solutions.
The LM2825 product line was designed for cost-sensitive, space-constrained industrial and embedded applications requiring fully integrated, easy-to-use DC-DC buck converters with minimal external components.
FAQ
What is the minimum input voltage required for stable operation of the LM2825N-ADJ?
The LM2825N-ADJ requires a minimum input voltage of 4.5V for guaranteed operation across temperature and load, as specified in the Operating Ratings table. This ensures sufficient headroom above the programmed output voltage plus dropout margin; for example, setting VOUT = 8V requires VIN ≥ 10V for reliable regulation per Application Information guidelines.
How do I calculate the feedback resistors R1 and R2 for a desired output voltage with the LM2825N-ADJ?
Use the equation VOUT = 1.23V × (1 + R2/R1), selecting R1 between 240Ω and 1.5kΩ for noise immunity and stability. For instance, to achieve 5V output: R2 = R1 × ((5/1.23) − 1) ≈ R1 × 3.07. With R1 = 1kΩ, R2 = 3.07kΩ (standard 3.09kΩ 1% metal film resistor). The LM2825N-ADJ datasheet confirms this method in the Programming Output Voltage section.
Does the LM2825N-ADJ support synchronous rectification?
No, the LM2825N-ADJ uses an internal N-channel MOSFET and external diode for freewheeling; it does not integrate a synchronous rectifier. The datasheet shows a standard buck topology with external Schottky diode in Figures 17 and 18, and specifies no synchronous control signals or timing requirements for a second switch.
What is the purpose of shorting pins 8 and 9 on the LM2825N-ADJ, and what additional component is required?
Shorting pins 8 and 9 on the LM2825N-ADJ reduces output ripple voltage by 25–33% by enabling an internal ripple reduction path. However, this configuration mandates a feed-forward capacitor (CFF) of 680–2700 pF between VOUT and ADJ pins to maintain loop stability, as explicitly required in the LM2825N-ADJ Application Information section.
Is the LM2825N-ADJ RoHS compliant and lead-free?
Yes, the LM2825N-ADJ/NOPB variant is RoHS compliant and lead-free, with "Green (RoHS & no Sb/Br)" eco plan and CU SN lead finish per TI's Package Option Addendum. The base part LM2825N-ADJ is marked LIFEBUY but shares identical packaging and compliance; both meet JEDEC Level-1 moisture sensitivity and RoHS substance restrictions.
LM2825N-ADJ Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- -
- Package/Case:
- 24-DIP (0.600", 15.24mm)
- Packaging:
- Tube
- Product Status:
- Obsolete
- Function:
- Step-Down
- Output Configuration:
- Positive
- Topology:
- Buck
- Output Type:
- Adjustable
- Number of Outputs:
- 1
- Voltage - Input (Min):
- 4.5V
- Voltage - Input (Max):
- 40V
- Voltage - Output (Min/Fixed):
- 1.23V
- Voltage - Output (Max):
- 15V
- Current - Output:
- 1A
- Frequency - Switching:
- 150kHz
- Synchronous Rectifier:
- No
- Operating Temperature:
- -40°C ~ 85°C (TA)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Through Hole
- Supplier Device Package:
- 24-PDIP
LM2825N-ADJ FAQ
1.How can I place an order for LM2825N-ADJ through Aetrix?
Please submit a Request for Quotation (RFQ) for LM2825N-ADJ 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 LM2825N-ADJ reliable?
The price and inventory of LM2825N-ADJ are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LM2825N-ADJ is usually 5 days.
3.What payment methods are accepted for LM2825N-ADJ?
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Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LM2825N-ADJ?
LM2825N-ADJ orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LM2825N-ADJ 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 LM2825N-ADJ?
For technical support, including LM2825N-ADJ datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LM2825N-ADJ requirements.
6.How does Aetrix verify that LM2825N-ADJ is sourced from the original manufacturer or authorized distributors?
All LM2825N-ADJ 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 LM2825N-ADJ meets industry standards.
7.What is the process for return or replacement of LM2825N-ADJ?
All LM2825N-ADJ units undergo pre-shipment inspection (PSI). If there is an issue with LM2825N-ADJ, 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 LM2825N-ADJ part is unused and in its original packaging.
Return procedure for LM2825N-ADJ:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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