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Texas Instruments LM2599S-12
- Part No.:
- LM2599S-12
- Manufacturer:
- Texas Instruments
- Package:
- TO-263-8, D2PAK (7 Leads + Tab), TO-263CA
- Datasheet:
-
LM2599S-12.pdf
- Description:
- IC REG BUCK 12V 3A TO263
- Quantity:
- Payment:
- Shipping:
Inventory:2,754
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Product details
Overview
LM2599S-12 from Texas Instruments is a monolithic 150 kHz step-down (buck) switching voltage regulator 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 is used in on-card DC/DC conversion for industrial power supplies and embedded systems requiring stable mid-power regulation.
For engineers reviewing the LM2599S-12 datasheet, LM2599S-12 pinout, LM2599S-12 application, or LM2599S-12 equivalent, key selection considerations include its fixed 12V output, TO-263-7 package thermal performance, 150 kHz fixed-frequency operation enabling compact magnetics, and built-in soft-start/shutdown control with error flag signaling.
Technical Context
The LM2599S-12 implements a current-mode PWM buck topology with internal 150 kHz oscillator, two-stage current limit protection, and voltage feedback via internal reference (not externally adjustable). Its control loop includes internal frequency compensation and operates across −40°C to +125°C junction temperature.
It features dedicated pins for shutdown/soft-start (SD/SS), delay timing (DELAY), and regulation error flag (FLAG), enabling system-level sequencing and fault monitoring without external logic. The device enters low-power standby mode (<200 μA IQ) when SD/SS is pulled low.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Output Voltage | Fixed 12 V ±4% over full line/load/temperature range - ensures stable rail for downstream logic or analog circuitry without external resistor network. |
| Max Output Current | 3 A continuous - supports mid-power applications such as FPGA core rails or motor driver logic supplies. |
| Input Voltage Range | 4.5 V to 40 V - accommodates wide-input industrial or automotive battery-derived supplies (e.g., 12 V nominal with transients). |
| Switching Frequency | 150 kHz fixed - enables use of standard off-the-shelf power inductors and reduces EMI compared to higher-frequency alternatives. |
| Efficiency | 90% at VIN = 25 V, IOUT = 3 A - minimizes thermal dissipation in space-constrained designs with moderate input-to-output differential. |
| Quiescent Current | 80 μA typical in shutdown - preserves battery life in always-on systems with controlled enable sequencing. |
| Thermal Resistance | θJA = 30 °C/W (TO-263 on 2.5 in² copper) - enables 3A operation without external heatsink under defined PCB layout conditions. |
Pinout & Package
LM2599S-12 is housed in a 7-pin TO-263 (KTW) surface-mount package with exposed thermal pad. Pin 1 is marked by tab orientation; pin numbering follows standard counterclockwise sequence starting from tab side.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 (VIN) | Input Power Supply | Accepts 4.5–40 V DC; requires local 470 μF low-ESR input capacitor to suppress switching transients. |
| 2 (OUT) | Switch Node / Power Output | Connects to catch diode anode and inductor; high dv/dt node requiring tight layout and ground plane isolation. |
| 3 (GND) | Power Ground | Main return path for switch current and IC bias; must be tied directly to thermal pad and low-inductance ground plane. |
| 4 (FEEDBACK) | Output Voltage Sense (N/C for fixed version) | No connection required - internally tied to 12 V output; unused in LM2599S-12 (fixed-voltage variant). |
| 5 (SD/SS) | Shutdown / Soft-Start Control | Pulled low (<0.6 V) disables regulator and reduces IQ to 80 μA; rising edge initiates soft-start ramp to prevent inrush. |
| 6 (DELAY) | Error Flag Timing Delay | Controls flag assertion delay time via external capacitor; sets response window for transient dropout detection. |
| 7 (FLAG) | Regulation Error Output | Open-collector active-low signal indicating >4% output deviation; sinks 3 mA max for direct LED or microcontroller interrupt. |
Key Features
| Feature | Design Value |
|---|---|
| Integrated Thermal Shutdown | Activates at TJ ≥ +150°C and latches off until thermal recovery - prevents permanent damage during sustained overload or poor heatsinking. |
| Two-Stage Current Limit | Peak switch current limited to 3.4–7.5 A range with foldback behavior - provides robust short-circuit protection while maintaining startup capability. |
| Out-of-Regulation Flag with Delay | FLAG asserts only after sustained dropout (>92% of nominal VOUT) for duration set by CDELAY - eliminates false triggers from brief load transients. |
| Soft-Start Function | Internal 2–3 V ramp on SD/SS pin controls output voltage rise time - limits inrush current into bulk output capacitance during power-up. |
| Low Standby Quiescent Current | 80 μA typical IQ in shutdown - enables use in battery-backed systems where long-term standby power budget is critical. |
Applications
| Industrial Power Supply | Automotive Body Control Module |
|---|---|
Use Scenario: Converting 24 V vehicle battery to stable 12 V rail for microcontroller, CAN transceiver, and sensor interface circuitry. IC Role / Device Role / Timing Role: Primary buck regulator providing isolated, regulated 12 V supply with fault signaling for system health monitoring. Use Value: FLAG pin enables real-time detection of alternator dropout or battery sag, allowing firmware to initiate safe shutdown before brownout. | Use Scenario: Generating 12 V from 12 V nominal battery (with 40 V load dump transients) for infotainment head unit logic rails. IC Role / Device Role / Timing Role: High-input-voltage buck converter with built-in 40 V absolute max rating and thermal protection for under-hood environments. Use Value: 40 V input rating and 30 °C/W θJA (with 2.5 in² copper) allow operation without external heatsink despite ambient temperatures up to +85°C. |
| Programmable Logic Controller (PLC) I/O Card | Test Equipment Auxiliary Supply |
Use Scenario: Providing isolated 12 V for digital I/O drivers and optocoupler interfaces on modular PLC backplanes. IC Role / Device Role / Timing Role: On-card DC/DC converter delivering 3 A with soft-start to prevent backplane voltage droop during hot-swap insertion. Use Value: SD/SS-controlled soft-start ensures controlled ramp-up of 12 V rail, avoiding bus contention or reset glitches during module insertion. | Use Scenario: Generating clean 12 V from lab bench supply for DUT biasing in automated test fixtures. IC Role / Device Role / Timing Role: Fixed-output buck regulator with low-noise operation and error flag for supply health verification in calibration sequences. Use Value: 90% efficiency at 25 V input reduces heat generation in enclosed test enclosures, improving long-term measurement stability. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar buck regulator applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LM2596S-12 | Lower 3A current rating, 150 kHz frequency, no FLAG or DELAY pins, TO-263-5 package | Lacks regulation error flag and delay timing - unsuitable for systems requiring fault logging or transient immunity tuning | Select LM2596S-12 only if FLAG functionality is unnecessary and board space allows for reduced feature set |
| MP2307DN-LF-Z | 3A, 12V fixed, 340 kHz switching, smaller SO-8EP package, no FLAG/DELAY, lower IQ (2.5 mA) | Higher frequency enables smaller inductors but increases EMI sensitivity; no fault signaling capability | Choose MP2307DN-LF-Z when PCB area is constrained and system-level fault monitoring is handled externally |
Compared with LM2596S-12 and MP2307DN-LF-Z, the LM2599S-12 uniquely delivers integrated regulation error flagging with user-adjustable delay, making it the only option among the three suitable for safety-aware or diagnostic-capable power architectures.
Availability
LM2599S-12 is available at Aetrix Electronics and suitable for industrial power supplies, automotive body electronics, and programmable logic controller (PLC) I/O modules requiring stable component supply with long-term manufacturability and consistent parametric performance.
Supply support for LM2599S-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 company headquartered in Dallas, Texas, specializing in analog, embedded processing, and power management technologies with broad industrial and automotive market focus.
The LM2599 series was designed as part of TI's SIMPLE SWITCHER® portfolio to simplify mid-power DC/DC design with minimal external components, targeting cost-sensitive yet reliability-critical applications like factory automation and transportation electronics.
FAQ
What is the maximum input voltage rating for the LM2599S-12?
The LM2599S-12 has an absolute maximum input voltage rating of 45 V, with recommended operating range from 4.5 V to 40 V. Operation above 40 V risks exceeding internal transistor breakdown limits and is not guaranteed per datasheet specifications. For 24 V nominal systems with load dump transients, the 40 V operating limit provides margin against common 35–40 V spikes.
Does the LM2599S-12 require external feedback resistors?
No, the LM2599S-12 does not require external feedback resistors. As a fixed-output variant, its 12 V regulation is implemented internally; the FEEDBACK pin is internally connected and must remain unconnected in circuit layout. External resistors are only required for the LM2599-ADJ version.
How does the FLAG pin function on the LM2599S-12?
The FLAG pin on the LM2599S-12 is an open-collector output that goes low when output voltage drops below 92–98% of nominal 12 V, with assertion delayed by the external CDELAY capacitor. It sinks up to 3 mA and is used for microcontroller interrupt signaling or LED status indication without requiring level-shifting circuitry.
Can the LM2599S-12 be used in parallel for higher current?
No, the LM2599S-12 is not designed for parallel operation. Its current-mode control lacks master-slave synchronization capability, and phase mismatch between units would cause instability and unequal current sharing. For >3 A requirements, select a single higher-current regulator such as the LM2678-12 or redesign with multiphase architecture.
What thermal performance can be expected from the LM2599S-12 in TO-263 package?
In the TO-263 (KTW) package, the LM2599S-12 achieves θJA = 30 °C/W when mounted on a double-sided PCB with 3 in² copper on the component side and 16 in² on the opposite side. This allows full 3 A output at ambient temperatures up to +75°C without external heatsink, assuming proper thermal pad soldering and via stitching per TI layout guidelines.
LM2599S-12 Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- SIMPLE SWITCHER®
- Package/Case:
- TO-263-8, D2PAK (7 Leads + Tab), TO-263CA
- Packaging:
- Tube
- 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)
LM2599S-12 FAQ
1.How can I place an order for LM2599S-12 through Aetrix?
Please submit a Request for Quotation (RFQ) for LM2599S-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 LM2599S-12 reliable?
The price and inventory of LM2599S-12 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LM2599S-12 is usually 5 days.
3.What payment methods are accepted for LM2599S-12?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LM2599S-12 transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LM2599S-12?
LM2599S-12 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LM2599S-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 LM2599S-12?
For technical support, including LM2599S-12 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LM2599S-12 requirements.
6.How does Aetrix verify that LM2599S-12 is sourced from the original manufacturer or authorized distributors?
All LM2599S-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 LM2599S-12 meets industry standards.
7.What is the process for return or replacement of LM2599S-12?
All LM2599S-12 units undergo pre-shipment inspection (PSI). If there is an issue with LM2599S-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 LM2599S-12 part is unused and in its original packaging.
Return procedure for LM2599S-12:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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