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Texas Instruments LM2677SX-3.3
- Part No.:
- LM2677SX-3.3
- Manufacturer:
- Texas Instruments
- Package:
- TO-263-8, D2PAK (7 Leads + Tab), TO-263CA
- Datasheet:
-
LM2677SX-3.3.pdf
- Description:
- IC REG BUCK 3.3V 5A TO263
- Quantity:
- Payment:
- Shipping:
Inventory:3,855
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Product details
Overview
LM2677SX-3.3 from Texas Instruments is a monolithic step-down (buck) switching voltage regulator with integrated 100 mΩ DMOS power switch, delivering up to 5A output current at a fixed 3.3V output voltage. It operates from 8V to 40V input, achieves up to 92% efficiency, and features ±2% output voltage tolerance over full line/load/temperature range. It is used in high-efficiency pre-regulator and battery charger applications requiring stable 3.3V rail generation.
For engineers reviewing the LM2677SX-3.3 datasheet, LM2677SX-3.3 pinout, LM2677SX-3.3 application, or LM2677SX-3.3 equivalent, key selection considerations include its 260 kHz fixed-frequency operation, ON/OFF control with 50 μA standby current, thermal shutdown, current limiting, and compatibility with external synchronization (280–400 kHz).
Technical Context
The LM2677SX-3.3 implements a current-mode PWM buck controller with internal 260 kHz oscillator and integrated 100 mΩ DMOS power switch. Its feedback loop uses a two-stage high-gain amplifier referenced to an internal 1.21 V bandgap, enabling precise regulation of the fixed 3.3V output without external resistors.
It supports external clock synchronization via the SYNC pin (pin 5), allowing ripple frequency control for EMI-sensitive systems. The BOOST capacitor (0.01 μF) enables gate overdrive for low RDS(ON), while the ON/OFF pin provides logic-level enable/disable with 1.4 V threshold and 50 μA quiescent draw in shutdown.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Output Voltage | Fixed 3.3 V ±2% over −40°C to +125°C junction temperature, 8–40 V input, 100 mA–5 A load. |
| Max Output Current | 5 A continuous; current limit threshold is 6.1–8.3 A, ensuring robust overload protection. |
| Input Voltage Range | 8 V to 40 V DC; absolute maximum rating is 45 V, supporting wide industrial and automotive supply rails. |
| Switching Frequency | 260 kHz fixed internal oscillator; externally synchronizable from 280 kHz to 400 kHz for EMI control. |
| Efficiency | Up to 92% at 12 VIN/5 A (for 12 V version); 82% typical at 12 VIN/5 A for LM2677SX-3.3 per datasheet test conditions. |
| Quiescent Current | 4.2 mA operating; drops to 50 μA in ON/OFF shutdown mode-critical for low-power standby systems. |
| Thermal Protection | Integrated thermal shutdown activates above +125°C junction temperature; auto-recovery on cooldown. |
Pinout & Package
LM2677SX-3.3 is packaged in the 7-lead DDPAK/TO-263 (package code KTW0007B), featuring an exposed die attach pad (DAP) that must be connected to PCB ground for thermal and electrical performance.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| VSW (Pin 1) | Switch Node | Drives external inductor; swings between VIN (switch ON) and ~−0.5 V (switch OFF via Schottky clamp); requires low-inductance layout. |
| VIN (Pin 2) | Power Input | Supplies bias and switch current; must be bypassed with low-ESR input capacitor placed adjacent to pin. |
| CBOOST (Pin 3) | Bootstrap Capacitor Terminal | Connects to VSW via 0.01 μF/50 V ceramic capacitor to generate gate drive > VIN for low RDS(ON). |
| GND (Pin 4) | Power Ground | Main return path for switch, bias, and feedback circuits; requires low-impedance ground plane connection. |
| SYNC (Pin 5) | External Clock Input | Accepts TTL/CMOS clock (280–400 kHz); AC-coupled via 100 pF + 1 kΩ to ground; disables foldback during sync. |
| FB (Pin 6) | Feedback Input | Internally biased to 1.21 V reference; direct connection to output suffices for fixed 3.3 V version. |
| ON/OFF (Pin 7) | Enable Control | Logic-compatible input; <0.8 V disables regulator (50 μA IQ); >2.0 V enables; internal 20 μA pull-up. |
Key Features
| Feature | Design Value |
|---|---|
| Integrated 100 mΩ DMOS Switch | Enables 5 A output without external MOSFET; reduces BOM count and layout complexity in high-current buck designs. |
| ±2% Output Voltage Accuracy | Guaranteed over full temperature, line, and load range-eliminates need for post-production trimming in precision 3.3 V systems. |
| 260 kHz Fixed-Frequency Operation | Provides predictable EMI profile and simplifies filter design; allows use of standard off-the-shelf inductors (e.g., 10 μH). |
| External Sync Capability (280–400 kHz) | Enables precise ripple frequency positioning for compliance with system-level spectral masks in comms/radio equipment. |
| 50 μA Standby Quiescent Current | Supports ultra-low-power sleep modes in battery-powered or energy-conscious applications without sacrificing fast wake-up. |
| Built-in Protection Suite | Includes thermal shutdown, cycle-by-cycle current limiting, and under-voltage lockout-reduces need for external fault management circuitry. |
Applications
| Industrial Power Pre-regulation | Telecom Line Card Supply |
|---|---|
Use Scenario: Generating a clean, efficient 3.3 V intermediate rail from a 24 V or 48 V backplane in programmable logic controllers or motor drives. IC Role / Device Role / Timing Role: Primary step-down regulator providing regulated 3.3 V to FPGAs, microcontrollers, and interface ICs. Use Value: Delivers 5 A at 82–92% efficiency with minimal external components, reducing heat sink requirements and board space vs. linear regulators. | Use Scenario: Powering DSPs, transceivers, and memory on telecom line cards where EMI must align with spectral emission limits. IC Role / Device Role / Timing Role: Synchronized buck converter whose output ripple frequency is locked to a system master clock. Use Value: External SYNC pin enables deterministic ripple placement at 300 kHz or 350 kHz, easing compliance with EN 55022 Class B conducted emissions. |
| Battery Charger Auxiliary Rail | Automotive Infotainment Core Supply |
Use Scenario: Providing isolated 3.3 V logic supply in multi-cell Li-ion battery chargers operating from variable DC bus (12–36 V). IC Role / Device Role / Timing Role: High-input-voltage buck regulator handling wide VIN range while maintaining tight output regulation during charge cycle transitions. Use Value: 8–40 V input range accommodates charger bus fluctuations; ±2% tolerance ensures reliable MCU and ADC operation across temperature. | Use Scenario: Powering infotainment SoCs and display controllers in vehicles where cold-crank (6 V) and load-dump (40 V) transients occur. IC Role / Device Role / Timing Role: Robust primary DC/DC converter with thermal shutdown and current limiting for automotive-grade reliability. Use Value: Absolute max 45 V input rating and −40°C to +125°C operation ensure functional safety during harsh automotive transients and ambient extremes. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar step-down regulator applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LM2678SX-3.3 | Same pinout, identical 3.3 V fixed output, but rated for 3 A (vs. 5 A); lower current limit (4.5 A) and higher RDS(ON) (150 mΩ). | Suitable only for ≤3 A loads; not recommended for high-current FPGA or SoC core rails requiring 5 A. | Select LM2678SX-3.3 only when load current is confirmed ≤3 A and board space/layout reuse is prioritized. |
| TPS54531 | 3.5–28 V input, 3.3 V adjustable via resistor divider; 5 A output; 570 kHz switching; smaller 8-pin SOIC package. | Lacks SYNC input and fixed 3.3 V option; requires external feedback resistors; higher frequency demands tighter layout control. | Choose TPS54531 for space-constrained designs needing higher switching frequency and adjustable output, but accept added design complexity. |
Compared with LM2678SX-3.3, the LM2677SX-3.3 delivers 67% higher current capability and lower conduction loss; versus TPS54531, it offers simpler fixed-output implementation and built-in SYNC for EMI control-but in a larger TO-263 package.
Availability
LM2677SX-3.3 is available at Aetrix Electronics and suitable for industrial power pre-regulation, telecom line card supply, battery charger auxiliary rails, and automotive infotainment core supplies requiring stable component supply and long-term manufacturability.
Supply support for LM2677SX-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 technologies, with decades of expertise in high-reliability power conversion ICs.
The LM2677 series belongs to TI's SIMPLE SWITCHER® family-designed specifically for ease-of-use in high-efficiency, medium-power DC/DC buck applications where minimal external components and rapid time-to-market are critical.
FAQ
What is the maximum input voltage rating for the LM2677SX-3.3?
The absolute maximum input voltage for the LM2677SX-3.3 is 45 V DC. However, the recommended operating range is 8 V to 40 V. Exceeding 40 V may trigger overvoltage stress or reduce reliability, especially under transient conditions. The device's internal protection does not guarantee safe operation beyond 45 V, so proper front-end filtering and clamping are advised in 48 V systems. Always verify derating margins per application environment.
Does the LM2677SX-3.3 require external feedback resistors to set its output voltage?
No, the LM2677SX-3.3 does not require external feedback resistors. It is a fixed-output variant with internal resistor divider network calibrated for 3.3 V ±2%. Pin 6 (FB) connects directly to the output node for regulation-no external components needed. This simplifies layout, improves accuracy, and eliminates resistor tolerance drift effects. Only the adjustable LM2677-ADJ version requires external resistors.
Can the LM2677SX-3.3 be synchronized to an external clock, and what are the timing constraints?
Yes, the LM2677SX-3.3 supports external synchronization via Pin 5 (SYNC). The acceptable input clock frequency range is 280 kHz to 400 kHz. The signal must be TTL- or CMOS-compatible (0 V to >3 V), AC-coupled using a 100 pF capacitor and terminated with a 1 kΩ resistor to ground. Synchronization disables current-limit foldback, so short-circuit protection remains active but with reduced headroom. Ensure the external clock's rising edge is clean and jitter-free for stable operation.
What thermal management guidance applies to the LM2677SX-3.3 in DDPAK/TO-263 package?
The LM2677SX-3.3 in DDPAK/TO-263 (KTW) package requires connection of the exposed Die Attach Pad (Pin 9/DAP) to a large PCB copper area for thermal dissipation. With 1.0064 in² copper (7.4× package area) and 12 vias to inner layers, θJA drops to 26°C/W. Without adequate copper, θJA rises to 56°C/W-risking thermal shutdown at full 5 A load. Thermal relief traces to the DAP must be minimized; solder mask opening over the pad is mandatory for optimal conduction.
How does the ON/OFF pin function, and what happens to quiescent current when disabled?
The ON/OFF pin (Pin 7) controls regulator enable state: voltages below 0.8 V disable the LM2677SX-3.3, reducing total input current to 50 μA typical. At 25°C, this standby current remains stable across temperature and input voltage. The pin features an internal 20 μA pull-up and 7 V zener clamp. When enabled (>2.0 V), full operation resumes instantly-no soft-start delay. Leaving the pin open defaults to ON due to internal pull-up, making it ideal for simple enable/disable control in battery-backed systems.
LM2677SX-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):
- 8V
- Voltage - Input (Max):
- 40V
- Voltage - Output (Min/Fixed):
- 3.3V
- Voltage - Output (Max):
- -
- Current - Output:
- 5A
- Frequency - Switching:
- 260kHz
- Synchronous Rectifier:
- No
- Operating Temperature:
- -40°C ~ 125°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- TO-263 (DDPAK-7)
LM2677SX-3.3 FAQ
1.How can I place an order for LM2677SX-3.3 through Aetrix?
Please submit a Request for Quotation (RFQ) for LM2677SX-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 LM2677SX-3.3 reliable?
The price and inventory of LM2677SX-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 LM2677SX-3.3 is usually 5 days.
3.What payment methods are accepted for LM2677SX-3.3?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LM2677SX-3.3 transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LM2677SX-3.3?
LM2677SX-3.3 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LM2677SX-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 LM2677SX-3.3?
For technical support, including LM2677SX-3.3 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LM2677SX-3.3 requirements.
6.How does Aetrix verify that LM2677SX-3.3 is sourced from the original manufacturer or authorized distributors?
All LM2677SX-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 LM2677SX-3.3 meets industry standards.
7.What is the process for return or replacement of LM2677SX-3.3?
All LM2677SX-3.3 units undergo pre-shipment inspection (PSI). If there is an issue with LM2677SX-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 LM2677SX-3.3 part is unused and in its original packaging.
Return procedure for LM2677SX-3.3:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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