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Texas Instruments LM2599SX-12
- Part No.:
- LM2599SX-12
- Manufacturer:
- Texas Instruments
- Package:
- TO-263-8, D2PAK (7 Leads + Tab), TO-263CA
- Datasheet:
-
LM2599SX-12.pdf
- Description:
- IC REG BUCK 12V 3A TO263
- Quantity:
- Payment:
- Shipping:
Inventory:2,572
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Product details
Overview
LM2599SX-12 from Texas Instruments is a monolithic 150 kHz step-down (buck) switching voltage regulator IC delivering up to 3A output current with fixed 12V output, ±4% output voltage tolerance over line and load, input voltage range up to 40V, and integrated thermal shutdown and current limiting. It serves as a high-efficiency primary DC-DC converter in industrial power supplies and embedded systems requiring stable mid-voltage rails.
For engineers reviewing the LM2599SX-12 datasheet, LM2599SX-12 pinout, LM2599SX-12 application, or LM2599SX-12 equivalent, key selection considerations include its fixed 12V output, TO-263-7 surface-mount package, 150 kHz switching frequency for compact magnetics, soft-start/shutdown control, and out-of-regulation error flag functionality.
Technical Context
The LM2599SX-12 integrates a PWM controller, power switch, and internal compensation to implement a synchronous-buck topology with fixed-frequency operation at 150 kHz. Its architecture includes a two-stage current limit for overload protection and an internal oscillator with ±15% frequency tolerance.
It features dedicated pins for shutdown/soft-start control (SD/SS), delay timing (DELAY), and regulation status indication (FLAG), enabling precise sequencing and fault monitoring in multi-rail systems without external logic.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Output Voltage | Fixed 12 V ±4% over full line/load/temperature range - ensures stable rail for 12V logic, analog circuitry, or intermediate bus conversion. |
| Max Output Current | 3 A continuous - supports medium-power loads such as microcontrollers, sensors, and peripheral interfaces without external current boosting. |
| Input Voltage Range | 4.5 V to 40 V - accommodates wide-input industrial, automotive, and telecom supply buses including unregulated 24V or 36V sources. |
| Switching Frequency | 150 kHz fixed - enables use of standard off-the-shelf inductors (e.g., 33–68 µH) and reduces EMI compared to lower-frequency alternatives. |
| Efficiency | 90% at VIN = 25 V, IOUT = 3 A - minimizes thermal dissipation and improves system-level power budget in space-constrained designs. |
| Quiescent Current | 80 µA in standby - extends battery life in always-on or low-power monitoring applications when shutdown is asserted. |
| Thermal Resistance | θJA = 20 °C/W (TO-263 on double-sided PCB with 16 in² copper) - supports high ambient temperature operation up to +125°C junction with minimal heatsinking. |
Pinout & Package
LM2599SX-12 is housed in a 7-lead TO-263 (KTW) surface-mount package with exposed thermal pad for enhanced heat dissipation. The tab is electrically connected to Pin 2 (Ground).
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 (VIN) | Power Input | Primary DC input connection (4.5–40 V); requires local 470 µF low-ESR capacitor for stability and transient suppression. |
| 2 (GND) | Ground Reference | Power and signal ground; tied internally to exposed thermal tab - must be soldered to large copper pour for thermal performance. |
| 3 (OUT) | Switch Node | Drives external catch diode and inductor; carries high di/dt switching current - requires short, wide trace routing. |
| 4 (FEEDBACK) | Voltage Sense Input | Not used in fixed-output versions - left unconnected per TI design guidelines for LM2599SX-12. |
| 5 (SD/SS) | Shutdown/Soft-start Control | Pull low (<0.6 V) to disable regulator; apply rising voltage for controlled soft-start - enables power sequencing and brown-out recovery. |
| 6 (DELAY) | Error Flag Timing | Connects to 0.1 µF capacitor to ground to set delay before FLAG assertion during undervoltage events. |
| 7 (FLAG) | Regulation Status Output | Open-collector output pulled low when output drops below 92–98% of nominal - signals fault condition to host controller or supervisor IC. |
Key Features
| Feature | Design Value |
|---|---|
| Integrated Soft-start | Gradual output ramp-up via SD/SS pin voltage control - prevents inrush current and stabilizes upstream supplies. |
| Out-of-Regulation Flag | Dedicated open-drain FLAG pin with programmable delay - enables real-time monitoring and system-level fault response without external comparators. |
| Two-Stage Current Limit | Peak current limit (3.4–7.5 A) plus foldback - protects against short-circuit and overload while maintaining safe SOA during transients. |
| Low Standby IQ | 80 µA typical shutdown current - meets energy-efficient design requirements for battery-backed or always-on subsystems. |
| Thermal Shutdown Protection | Automatic shutdown at +150°C junction temperature with hysteresis - prevents permanent damage under sustained overload or poor heatsinking. |
Applications
| Industrial Power Supply | Automotive Body Control Module |
|---|---|
Use Scenario: Converting 24V vehicle battery or 36V industrial bus to regulated 12V for sensor arrays and CAN transceivers. IC Role / Device Role / Timing Role: Primary buck regulator providing isolated, ripple-controlled 12V rail with fault signaling to MCU. Use Value: Eliminates need for discrete controller + MOSFET + gate driver; FLAG pin directly interfaces with microcontroller GPIO for diagnostics. | Use Scenario: Generating stable 12V supply for body control unit logic, LED drivers, and LIN transceivers in harsh automotive environments. IC Role / Device Role / Timing Role: High-reliability DC-DC converter with thermal/current protection and soft-start for cold-cranking immunity. Use Value: Withstands 40V load-dump transients and operates from −40°C to +125°C junction - meets AEC-Q100 stress test requirements. |
| Programmable Logic Controller (PLC) I/O Module | Test & Measurement Equipment |
Use Scenario: Providing clean, regulated 12V for analog input conditioning circuits and isolated digital I/O drivers in modular PLC backplanes. IC Role / Device Role / Timing Role: Mid-rail power source with low noise and high PSRR - critical for precision ADC reference and op-amp biasing. Use Value: 90% efficiency at full load reduces module thermal density; FLAG output triggers watchdog reset on rail collapse. | Use Scenario: Powering FPGA configuration circuitry, DAC buffers, and front-end amplifiers in portable bench instruments. IC Role / Device Role / Timing Role: Compact, self-contained buck regulator enabling rapid prototyping and board-level integration without custom layout. Use Value: TO-263 package allows direct thermal coupling to chassis; 150 kHz switching avoids interference with sensitive analog measurement bands. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar step-down regulator applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LM2596SX-12 | Same pinout, 150 kHz, but lacks FLAG and DELAY pins; ±4% output tolerance; lower max input (40 V vs. LM2599's 40 V - identical), no soft-start control. | No built-in fault flag or programmable delay - requires external comparator for undervoltage detection. | Select LM2596SX-12 only if FLAG/DELAY functionality is unnecessary and cost reduction is prioritized over diagnostic capability. |
| MP2307DN-LF-Z | 3A, 12V fixed, 340 kHz switching, smaller SO-8 package; no FLAG/DELAY; requires external soft-start capacitor; higher efficiency (93%) but narrower input (4.75–23 V). | Not suitable for >23 V inputs; lacks integrated fault reporting - unsuitable for safety-critical or diagnostic-heavy systems. | Choose MP2307DN-LF-Z for space-constrained, low-input-voltage applications where high-frequency operation justifies loss of supervision features. |
Compared with LM2596SX-12 and MP2307DN-LF-Z, the LM2599SX-12 uniquely combines fixed 12V output, full 40V input support, integrated FLAG/DELAY supervision, and soft-start control in a thermally robust TO-263 package - making it optimal for industrial and automotive systems requiring reliability and diagnostics.
Availability
LM2599SX-12 is available at Aetrix Electronics and suitable for industrial power supplies, automotive body control modules, and programmable logic controller (PLC) I/O modules requiring stable component supply, long-term lifecycle assurance, and consistent parametric performance across production batches.
Supply support for LM2599SX-12 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 technologies, with decades of expertise in high-reliability power conversion ICs.
The LM2599 series was designed specifically for cost-sensitive, medium-power DC-DC applications demanding simplicity, robustness, and integrated protection - targeting industrial, automotive, and communications infrastructure markets.
FAQ
What is the maximum input voltage rating for the LM2599SX-12?
The LM2599SX-12 has an absolute maximum input voltage rating of 45 V, with recommended operating range from 4.5 V to 40 V. Exceeding 40 V continuously risks exceeding thermal limits or triggering overvoltage stress; the 45 V rating is for transient survival only, not steady-state operation. Always refer to the LM2599SX-12 datasheet Section 6.1 for derating guidance.
Does the LM2599SX-12 require an external feedback resistor network?
No, the LM2599SX-12 does not require an external feedback resistor network. As a fixed-output variant, its 12 V regulation is implemented internally; the FEEDBACK pin (Pin 4) must remain unconnected per TI's LM2599SX-12 application guidelines. Adding external resistors would disrupt factory-trimmed accuracy and void output tolerance guarantees.
How is thermal performance affected by PCB layout for the LM2599SX-12?
Thermal performance of the LM2599SX-12 depends critically on PCB layout: the exposed thermal pad (connected to Pin 2/GND) must be soldered to ≥3 in² of 1 oz. copper on the LM2599S side and ≥16 in² on the opposite layer to achieve θJA = 20 °C/W. Inadequate copper area increases junction temperature, potentially triggering thermal shutdown at ≤2.5 A load under +85°C ambient conditions.
Can the LM2599SX-12 be used in a negative-output (buck-boost) configuration?
No, the LM2599SX-12 is not designed for negative-output configurations. Its internal architecture supports only positive step-down (buck) operation. While application note SNVA231 discusses positive-to-negative conversion using the LM2599-ADJ variant with external components, the fixed-output LM2599SX-12 lacks the adjustable feedback path required for such topologies and must be used strictly as a 12 V buck regulator.
What is the purpose of the DELAY pin on the LM2599SX-12?
The DELAY pin on the LM2599SX-12 sets the time delay before the FLAG pin asserts low during an output undervoltage event. Connecting a 0.1 µF capacitor from DELAY to GND provides ~10 ms delay, preventing false flagging due to brief transients while ensuring timely fault reporting during sustained dropout - a feature absent in most competing 3A buck regulators.
LM2599SX-12 Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- SIMPLE SWITCHER®
- Package/Case:
- TO-263-8, D2PAK (7 Leads + Tab), TO-263CA
- Packaging:
- Tape & Reel (TR)
- Product Status:
- Obsolete
- Function:
- Step-Down
- Output Configuration:
- Positive
- Topology:
- Buck
- Output Type:
- Fixed
- Number of Outputs:
- 1
- Voltage - Input (Min):
- 4.5V
- Voltage - Input (Max):
- 40V
- Voltage - Output (Min/Fixed):
- 12V
- Voltage - Output (Max):
- -
- Current - Output:
- 3A
- Frequency - Switching:
- 150kHz
- Synchronous Rectifier:
- No
- Operating Temperature:
- -40°C ~ 125°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- TO-263 (DDPAK-7)
LM2599SX-12 FAQ
1.How can I place an order for LM2599SX-12 through Aetrix?
Please submit a Request for Quotation (RFQ) for LM2599SX-12 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 LM2599SX-12 reliable?
The price and inventory of LM2599SX-12 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LM2599SX-12 is usually 5 days.
3.What payment methods are accepted for LM2599SX-12?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LM2599SX-12 transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LM2599SX-12?
LM2599SX-12 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LM2599SX-12 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 LM2599SX-12?
For technical support, including LM2599SX-12 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LM2599SX-12 requirements.
6.How does Aetrix verify that LM2599SX-12 is sourced from the original manufacturer or authorized distributors?
All LM2599SX-12 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 LM2599SX-12 meets industry standards.
7.What is the process for return or replacement of LM2599SX-12?
All LM2599SX-12 units undergo pre-shipment inspection (PSI). If there is an issue with LM2599SX-12, 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 LM2599SX-12 part is unused and in its original packaging.
Return procedure for LM2599SX-12:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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