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Texas Instruments LM2677SX-ADJ
- Part No.:
- LM2677SX-ADJ
- Manufacturer:
- Texas Instruments
- Package:
- TO-263-8, D2PAK (7 Leads + Tab), TO-263CA
- Datasheet:
-
LM2677SX-ADJ.pdf
- Description:
- IC REG BUCK ADJ 5A TO263
- Quantity:
- Payment:
- Shipping:
Inventory:1,699
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Product details
Overview
LM2677SX-ADJ from Texas Instruments is a monolithic step-down (buck) DC/DC switching regulator IC with integrated 100 mΩ DMOS power switch, delivering up to 5A output current across an adjustable output range of 1.2V to 37V. It operates from 8V to 40V input, achieves up to 92% efficiency, and features ±2% output voltage tolerance over full line/load/temperature conditions. It is used in high-efficiency pre-regulators for telecom power systems.
For engineers reviewing the LM2677SX-ADJ datasheet, LM2677SX-ADJ pinout, LM2677SX-ADJ application, or LM2677SX-ADJ equivalent, key selection criteria include its 260 kHz fixed-frequency PWM control, ON/OFF enable functionality, external sync capability (280–400 kHz), thermal shutdown, and current-limit protection - all critical for industrial and communications power supply design.
Technical Context
The LM2677SX-ADJ implements a voltage-mode PWM controller with internal 260 kHz oscillator and external sync input (Pin 5), enabling precise ripple frequency control for EMI-sensitive applications. Its feedback loop senses output voltage via resistive divider at Pin 6 (FB), referenced to 1.21 V typical VFB, supporting wide-range programmability.
It integrates a low-RDS(ON) (0.12–0.225 Ω) DMOS power switch, boost capacitor drive (Pin 3), and ON/OFF logic (Pin 7) that reduces quiescent current to 50 μA in shutdown. Thermal shutdown and cycle-by-cycle current limiting (6.1–8.75 A) provide robust fault protection without external circuitry.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Output Current | 5 A continuous - supports high-power industrial loads without external current boosting. |
| Input Voltage Range | 8 V to 40 V - compatible with 12 V, 24 V, and 36 V nominal bus systems including automotive and telecom inputs. |
| Output Voltage Range | 1.2 V to 37 V (adjustable) - set via external resistor divider on FB pin; enables single-IC flexibility across diverse system rails. |
| Feedback Reference Voltage | 1.21 V (±2.9%) - defines output accuracy; determines VOUT = 1.21 × (1 + R1/R2) with minimal drift over −40°C to +125°C. |
| Switching Frequency | 260 kHz fixed (internal) or 280–400 kHz (external sync) - balances efficiency, size, and EMI; allows consistent filter design across platforms. |
| Efficiency | Up to 92% - achieved via 100 mΩ RDS(ON) DMOS switch and optimized gate drive; reduces thermal load in enclosed enclosures. |
| Quiescent Current | 4.2 mA active / 50 μA standby - enables low-power hold-up modes during system sleep without auxiliary LDOs. |
Pinout & Package
LM2677SX-ADJ is packaged in DDPAK/TO-263 (Package Number KTW0007B), a thermally enhanced 7-pin surface-mount package with exposed die attach pad (DAP) for PCB ground connection and improved thermal dissipation (θJA as low as 26°C/W with 7.4× copper area).
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| VIN (Pin 2) | Power Input | Primary DC input (8–40 V); supplies both load energy and internal bias; requires local 0.1–0.47 µF ceramic + bulk capacitor. |
| VSW (Pin 1) | Switch Node | Drain of internal DMOS switch; connects to inductor and catch diode anode; swings between VIN and ~−0.5 V. |
| CBOOST (Pin 3) | Bootstrap Capacitor Terminal | Connects 0.01 µF/50 V ceramic capacitor to VSW; generates gate drive >VIN to fully enhance internal MOSFET. |
| GND (Pin 4) | Power Ground | Common return for power path and internal circuits; must be tied to low-impedance ground plane to minimize noise coupling. |
| SYNC (Pin 5) | External Clock Input | Accepts TTL/CMOS clock (280–400 kHz); resets internal oscillator on rising edge; disables current limit foldback when active. |
| FB (Pin 6) | Feedback Input | Senses output voltage via resistor divider; regulates VOUT to 1.21 V reference; high-impedance (85 nA bias current). |
| ON/OFF (Pin 7) | Enable Control | Active-high logic input; <0.8 V disables regulator (50 µA IQ); internal 20 µA pull-up; max 6 V absolute rating. |
Key Features
| Feature | Design Value |
|---|---|
| Integrated 100 mΩ DMOS Power Switch | Eliminates need for external high-current MOSFET and driver; reduces BOM count and layout complexity in 5 A buck designs. |
| Adjustable Output (1.2 V to 37 V) | Single part replaces multiple fixed-output variants; simplifies inventory and enables flexible rail generation in multi-voltage systems. |
| External Sync Capability (280–400 kHz) | Enables deterministic EMI placement and synchronized switching across multiple converters - essential for radio and comms equipment. |
| Thermal Shutdown & Cycle-by-Cycle Current Limit | Provides autonomous fault recovery without external sensing; protects against overload, short-circuit, and overheating in unattended operation. |
| 50 µA Standby Quiescent Current | Supports ultra-low-power system states; enables battery-backed or energy-harvesting applications where idle consumption matters. |
Applications
| Industrial Power Pre-regulator | Telecom DC-DC Converter |
|---|---|
|
Use Scenario: Converts 24 V or 48 V telecom rectified bus to intermediate 5 V or 12 V rail feeding point-of-load regulators. IC Role / Device Role / Timing Role: Primary step-down regulator providing stable, high-current intermediate voltage with tight line/load regulation. Use Value: Delivers 5 A at >92% efficiency, reducing heat sink requirements and improving system power density in compact chassis. |
Use Scenario: Powers baseband processing modules in wireless infrastructure equipment requiring clean, regulated 3.3 V or adjustable rails. IC Role / Device Role / Timing Role: Synchronized buck converter operating at 350 kHz to avoid interference with RF bands and simplify EMI filtering. Use Value: External SYNC input enables co-location with other converters without beat-frequency ripple; ±2% output tolerance ensures signal integrity. |
| Battery Charger Front-End | Programmable Lab Power Supply |
|
Use Scenario: Regulates variable-input voltage (e.g., 12–36 V solar or vehicle battery) to constant-current/constant-voltage charging profile. IC Role / Device Role / Timing Role: Adjustable-output buck stage controlling charge voltage (e.g., 14.4 V for LiFePO4) with ON/OFF sequencing. Use Value: 1.21 V feedback reference and wide VOUT range allow precise, temperature-compensated charging voltages using standard resistor networks. |
Use Scenario: Core regulation stage in benchtop power supplies requiring user-adjustable output from 1.2 V to 30 V at 5 A. IC Role / Device Role / Timing Role: Main DC-DC controller with front-panel potentiometer-based feedback divider and remote ON/OFF control. Use Value: Integrated current limit and thermal shutdown provide inherent overcurrent/overtemperature protection without added comparators or sensors. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar step-down regulator applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LM2678-ADJ | Same architecture but rated for 3 A output; lower RDS(ON) (0.11 Ω typ) and higher efficiency at light loads; no SYNC pin. | Best suited for space-constrained or lower-current (<3 A) designs where sync is not required and thermal budget is tighter. | Select LM2678-ADJ only if load current ≤3 A and external synchronization is unnecessary. |
| TPS54560B | 60 V input, 5 A, adjustable output; 100 kHz–2.5 MHz sync-capable; integrated soft-start and precision enable threshold (1.22 V). | Preferred for wider input ranges (e.g., 8–60 V), higher-frequency operation (>400 kHz), or designs needing programmable soft-start and tighter enable control. | Choose TPS54560B when input exceeds 40 V, higher switching frequencies are needed, or advanced sequencing features are required. |
Compared with LM2677SX-ADJ, LM2678-ADJ offers lower conduction loss at reduced current but lacks sync capability, while TPS54560B extends input voltage and frequency range at the cost of higher BOM complexity and different compensation behavior.
Availability
LM2677SX-ADJ is available at Aetrix Electronics and suitable for industrial power pre-regulators, telecom DC-DC converters, and battery charger front-ends requiring stable component supply, long-lifecycle support, and traceable sourcing.
Supply support for LM2677SX-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 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 non-isolated buck applications, minimizing external components while maintaining high efficiency and ruggedness for industrial and communications systems.
FAQ
What is the maximum output voltage supported by the LM2677SX-ADJ?
The LM2677SX-ADJ supports an adjustable output voltage range from 1.2 V to 37 V, set by an external resistor divider connected to the FB pin. This range is validated per the datasheet's "LM2677-ADJ Electrical Characteristics" table, with feedback reference voltage specified as 1.21 V (min 1.174 V, max 1.246 V) across −40°C to +125°C junction temperature.
Does the LM2677SX-ADJ require an external bootstrap capacitor?
Yes, the LM2677SX-ADJ requires a 0.01 µF/50 V ceramic capacitor connected between the CBOOST pin (Pin 3) and the VSW pin (Pin 1). This capacitor provides gate-boost voltage above VIN to fully enhance the internal DMOS switch, ensuring low RDS(ON) and high efficiency - a requirement explicitly stated in the "APPLICATION HINTS" section of the SNVS077I datasheet.
Can the LM2677SX-ADJ synchronize to an external clock, and what is the valid frequency range?
Yes, the LM2677SX-ADJ supports external synchronization via the SYNC pin (Pin 5) over 280 kHz to 400 kHz. The datasheet specifies that the external clock must exceed the internal oscillator's upper limit (280 kHz) to prevent erroneous reset; it also notes that current limit foldback is disabled during sync mode - a critical design consideration confirmed in the "APPLICATION HINTS" section.
What thermal performance can be expected from the LM2677SX-ADJ in DDPAK/TO-263 package?
In the DDPAK/TO-263 (KTW) package, the LM2677SX-ADJ achieves a junction-to-ambient thermal resistance (θJA) as low as 26°C/W when mounted on 1.0064 in² copper area with vias - per the "All Output Voltage Versions Electrical Characteristics" table. This enables reliable 5 A operation at ambient temperatures up to +85°C without forced airflow, assuming proper PCB copper layout per TI Application Note AN-1187.
How does the ON/OFF pin function on the LM2677SX-ADJ, and what is its threshold voltage?
The ON/OFF pin (Pin 7) is an active-high enable input with a typical threshold voltage of 1.4 V (min 0.8 V, max 2.0 V). Driving this pin below 0.8 V disables the regulator, reducing quiescent current to 50 µA. The pin features an internal 20 µA pull-up and 7 V clamp zener, allowing direct microcontroller GPIO control without level-shifting - details verified in the "All Output Voltage Versions Electrical Characteristics" and "APPLICATION HINTS" sections.
LM2677SX-ADJ 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:
- Adjustable
- Number of Outputs:
- 1
- Voltage - Input (Min):
- 8V
- Voltage - Input (Max):
- 40V
- Voltage - Output (Min/Fixed):
- 1.21V
- Voltage - Output (Max):
- 37V
- 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-ADJ FAQ
1.How can I place an order for LM2677SX-ADJ through Aetrix?
Please submit a Request for Quotation (RFQ) for LM2677SX-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 LM2677SX-ADJ reliable?
The price and inventory of LM2677SX-ADJ are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LM2677SX-ADJ is usually 5 days.
3.What payment methods are accepted for LM2677SX-ADJ?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LM2677SX-ADJ transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LM2677SX-ADJ?
LM2677SX-ADJ orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LM2677SX-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 LM2677SX-ADJ?
For technical support, including LM2677SX-ADJ datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LM2677SX-ADJ requirements.
6.How does Aetrix verify that LM2677SX-ADJ is sourced from the original manufacturer or authorized distributors?
All LM2677SX-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 LM2677SX-ADJ meets industry standards.
7.What is the process for return or replacement of LM2677SX-ADJ?
All LM2677SX-ADJ units undergo pre-shipment inspection (PSI). If there is an issue with LM2677SX-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 LM2677SX-ADJ part is unused and in its original packaging.
Return procedure for LM2677SX-ADJ:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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