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Texas Instruments LM2599SX-3.3
- Part No.:
- LM2599SX-3.3
- Manufacturer:
- Texas Instruments
- Package:
- TO-263-8, D2PAK (7 Leads + Tab), TO-263CA
- Datasheet:
-
LM2599SX-3.3.pdf
- Description:
- IC REG BUCK 3.3V 3A TO263
- Quantity:
- Payment:
- Shipping:
Inventory:3,061
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Product details
Overview
LM2599SX-3.3 from Texas Instruments is a monolithic 3A step-down (buck) switching voltage regulator with fixed 3.3V output, 150 kHz internal oscillator, input voltage range up to 40V, ±4% output voltage tolerance over line and load, and thermal shutdown/current limit protection. It delivers stable power in industrial DC/DC conversion where compact size and high efficiency are required.
For engineers reviewing the LM2599SX-3.3 datasheet, LM2599SX-3.3 pinout, LM2599SX-3.3 application, or LM2599SX-3.3 equivalent, key selection criteria include output current capability (3A), fixed 3.3V regulation accuracy, TO-263 surface-mount package thermal performance, and integrated soft-start/shutdown control for reliable system power sequencing.
Technical Context
The LM2599SX-3.3 implements a current-mode PWM buck topology with internal 150 kHz oscillator, enabling use of standard off-the-shelf inductors and minimizing external component count. Its two-stage current limit and thermal shutdown provide fault protection without external circuitry.
It features an out-of-regulation error flag with programmable delay, soft-start via the SS/SD pin, and low 80 μA standby quiescent current. The feedback loop uses internal reference (not accessible externally), and output voltage is factory-trimmed to 3.3V with guaranteed ±4% tolerance across −40°C to +125°C junction temperature.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Output Voltage | Fixed 3.3V ±4% (3.135V–3.465V min/max over full temp/load) |
| Max Output Current | 3A continuous - supports mid-power embedded rails without external current boosting |
| Input Voltage Range | 4.5V to 40V - compatible with 5V, 12V, 24V, and 36V industrial bus inputs |
| Switching Frequency | 150 kHz fixed - enables use of low-cost, widely available 33–68 μH inductors |
| Efficiency | 73% at VIN = 12V, IOUT = 3A - balances thermal dissipation and board area in space-constrained designs |
| Quiescent Current | 80 μA in shutdown - suitable for battery-backed or low-power standby systems |
| Thermal Resistance | θJA = 30°C/W (TO-263 on 2.5 in² copper) - enables 3A operation without external heatsink under typical PCB layout |
Pinout & Package
LM2599SX-3.3 is housed in a 7-lead TO-263 (KTW) surface-mount package with exposed thermal pad. The package supports high-current routing and efficient heat transfer to PCB copper.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| IN | Input voltage supply | Accepts 4.5–40V DC; requires local 470 μF low-ESR input capacitor for stability |
| OUT | Regulated output | Delivers fixed 3.3V; connects directly to output inductor and catch diode anode |
| GND | Power ground | Common return for input/output paths and IC internal circuits; must be low-inductance connection |
| FB | Feedback (not used) | No connection - internally tied to 3.3V reference; not accessible in fixed-output version |
| SD/SS | Shutdown/Soft-start control | Pull ≤0.6V to disable regulator (80 μA IQ); apply 2–3V ramp for controlled soft-start |
| FLAG | Error flag output | Open-drain active-low signal asserted when VOUT drops below 92–98% of nominal |
| DELAY | Flag delay timing | Connect 0.1 μF to GND to set ~10 ms delay before FLAG asserts during dropout |
Key Features
| Feature | Design Value |
|---|---|
| Integrated soft-start | Programmable via SD/SS pin voltage ramp - prevents inrush current and output overshoot during power-up |
| Out-of-regulation detection | Dedicated FLAG pin with user-settable delay - enables system-level fault monitoring and graceful shutdown |
| Two-stage current limiting | Peak current limit (3.4–3.6A min) plus foldback - protects switch during short-circuit without latch-up |
| Thermal shutdown | Activates at TJ ≥ +150°C with hysteresis - ensures safe recovery after overload or poor heatsinking |
| Low-noise switching | Fixed 150 kHz frequency - avoids EMI-sensitive bands (e.g., AM radio) and simplifies filter design |
Applications
| Industrial PLC Power Supply | Embedded System Pre-regulator |
|---|---|
|
Use Scenario: Provides clean 3.3V rail for microcontroller, FPGA, and I/O logic in DIN-rail mounted programmable logic controllers operating from 24V DC field bus. IC Role / Device Role / Timing Role: Primary buck converter delivering regulated 3.3V at up to 3A, replacing linear regulators to reduce thermal load and improve efficiency. Use Value: Eliminates need for external current sense or protection ICs; FLAG output interfaces directly with PLC watchdog circuitry for fault reporting. |
Use Scenario: Generates stable 3.3V intermediate supply for LDOs powering sensitive analog and RF subsystems in wireless gateways. IC Role / Device Role / Timing Role: High-efficiency pre-regulator stepping down 12V or 24V system rail before final low-noise LDO stage. Use Value: 73% efficiency at full load reduces heat generation upstream of noise-sensitive components; soft-start prevents LDO input transients. |
| On-Card DC/DC Converter | Positive-to-Negative Inverter |
|
Use Scenario: Integrated 3.3V power solution on dense compute modules where board space is constrained and thermal management is limited. IC Role / Device Role / Timing Role: Standalone buck regulator using TO-263 package's thermal pad for direct PCB conduction cooling. Use Value: θJA = 30°C/W with 2.5 in² copper allows full 3A output without heatsink - reduces BOM and assembly cost. |
Use Scenario: Generates −3.3V rail from +12V input for op-amp biasing or RS-232 interface circuits in instrumentation systems. IC Role / Device Role / Timing Role: Configured in inverting buck-boost topology using external inductor and diode; leverages fixed 3.3V reference for precise negative output magnitude. Use Value: Maintains ±4% output accuracy even with varying input and load - critical for precision analog signal conditioning. |
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-3.3 | Lower 1.5A output current; 150 kHz frequency; same TO-263 package but no FLAG/DELAY pins | Lacks error flag and programmable delay - unsuitable for safety-monitored or fault-reporting systems | Select LM2596SX-3.3 only for cost-sensitive, lower-current applications where supervision is unnecessary |
| TPS54302DDAR | 3A synchronous buck; 2.5–6V input; 500 kHz switching; integrated high/low-side MOSFETs; no FLAG pin | Requires external compensation; narrower input range; higher efficiency above 5V input but incompatible with 12–40V industrial buses | Choose TPS54302DDAR for compact, high-frequency designs powered from 3.3–5V sources - not a drop-in replacement for LM2599SX-3.3 |
Compared with LM2596SX-3.3, the LM2599SX-3.3 provides 2× output current and integrated fault signaling; versus TPS54302DDAR, it offers wider input range and simpler layout at the expense of switching frequency flexibility and synchronous rectification.
Availability
LM2599SX-3.3 is available at Aetrix Electronics and suitable for industrial automation, embedded computing, and instrumentation requiring stable component supply, long-term lifecycle support, and consistent parametric performance across production batches.
Supply support for LM2599SX-3.3 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 solutions, with decades of expertise in high-reliability power conversion ICs.
The LM2599 series was designed specifically for robust, low-component-count DC/DC buck conversion in industrial, automotive, and telecom infrastructure - prioritizing fault resilience, thermal performance, and ease of implementation over ultra-high efficiency.
FAQ
What is the maximum input voltage rating for the LM2599SX-3.3?
The absolute maximum input voltage for the LM2599SX-3.3 is 45V, but the recommended operating range is 4.5V to 40V per the datasheet. Exceeding 40V may compromise reliability or trigger overvoltage stress on internal components. For sustained operation, maintain VIN ≤ 40V with appropriate derating for ambient temperature and PCB thermal design.
Does the LM2599SX-3.3 require an external feedback resistor network?
No, the LM2599SX-3.3 does not require external feedback resistors. As a fixed-output variant, its 3.3V regulation is achieved via internal trimming - the FB pin is unconnected and internally tied to the reference. External resistors are only needed for the adjustable LM2599-ADJ version.
How is thermal performance affected by PCB copper area for the LM2599SX-3.3?
Thermal resistance θJA for the LM2599SX-3.3 varies significantly with PCB copper: 50°C/W with minimal copper, 30°C/W with 2.5 in² single-sided copper, and as low as 20°C/W with double-sided copper and thermal vias. Full 3A operation at +125°C ambient requires ≥2.5 in² of 1 oz. copper connected to the TO-263 thermal pad.
Can the LM2599SX-3.3 be used in a negative-output configuration?
Yes, the LM2599SX-3.3 can be configured as a positive-to-negative inverter using a standard buck-boost topology with external inductor and diode. Its fixed 3.3V reference enables accurate −3.3V output magnitude, and the FLAG pin retains dropout detection functionality for the negative rail when properly biased.
What is the purpose of the DELAY pin on the LM2599SX-3.3?
The DELAY pin sets the response time of the FLAG output during output undervoltage events. Connecting a 0.1 μF capacitor from DELAY to GND introduces ~10 ms delay before FLAG asserts, preventing false triggers during brief transients such as motor startup or capacitor charging surges in the LM2599SX-3.3 power system.
LM2599SX-3.3 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):
- 3.3V
- 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-3.3 FAQ
1.How can I place an order for LM2599SX-3.3 through Aetrix?
Please submit a Request for Quotation (RFQ) for LM2599SX-3.3 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-3.3 reliable?
The price and inventory of LM2599SX-3.3 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LM2599SX-3.3 is usually 5 days.
3.What payment methods are accepted for LM2599SX-3.3?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LM2599SX-3.3 transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LM2599SX-3.3?
LM2599SX-3.3 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LM2599SX-3.3 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-3.3?
For technical support, including LM2599SX-3.3 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LM2599SX-3.3 requirements.
6.How does Aetrix verify that LM2599SX-3.3 is sourced from the original manufacturer or authorized distributors?
All LM2599SX-3.3 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-3.3 meets industry standards.
7.What is the process for return or replacement of LM2599SX-3.3?
All LM2599SX-3.3 units undergo pre-shipment inspection (PSI). If there is an issue with LM2599SX-3.3, 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-3.3 part is unused and in its original packaging.
Return procedure for LM2599SX-3.3:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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