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Texas Instruments LM2738XSDX/NOPB
- Part No.:
- LM2738XSDX/NOPB
- Manufacturer:
- Texas Instruments
- Package:
- 8-WFDFN Exposed Pad
- Datasheet:
-
LM2738XSDX/NOPB.pdf
- Description:
- IC REG BUCK ADJ 1.5A 8WSON
- Quantity:
- Payment:
- Shipping:
Inventory:4,139
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Product details
Overview
LM2738XSDX/NOPB from Texas Instruments is a monolithic 1.6-MHz, current-mode PWM step-down DC-DC regulator delivering 1.5-A output current with 250-mΩ internal NMOS switch, 0.8-V ±2% reference, and 400-nA shutdown current. It operates from 3-V to 20-V input and supports 0.8-V to 18-V adjustable output voltage, targeting space-constrained point-of-load applications in USB-powered devices and DSL modems.
For engineers reviewing the LM2738XSDX/NOPB datasheet, LM2738XSDX/NOPB pinout, LM2738XSDX/NOPB application, or LM2738XSDX/NOPB equivalent, key selection considerations include verified 1.6-MHz fixed switching frequency, WSON-8 package thermal performance (RθJA = 45.9°C/W), cycle-by-cycle current limit (2.9 A typ), internal soft-start (600 µs ramp), and output overvoltage protection (16% above VREF).
Technical Context
The LM2738XSDX/NOPB implements constant-frequency current-mode control with internal compensation, enabling stable regulation across wide load and line variations without external loop components. Its architecture integrates a bootstrap gate-drive circuit (requiring external BOOST capacitor and diode) to sustain NMOS switch conduction at high duty cycles while maintaining VBOOST–VSW between 2.5 V and 5.5 V.
Functional safety features include undervoltage lockout (2.7 V rising threshold, 400 mV hysteresis), thermal shutdown (165°C trip, 150°C recovery), and cycle-by-cycle current limiting. The device uses a single-ended synchronous rectification topology with external Schottky catch diode and supports resistive feedback networks for precise output voltage setting via the FB pin.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Switching Frequency | 1.6 MHz (fixed, LM2738X variant) - enables use of sub-3-mm surface-mount inductors and ceramic capacitors |
| Output Current | 1.5 A continuous - supports local core power for HDDs and set-top boxes without external pass devices |
| Input Voltage Range | 3 V to 20 V - accommodates 5-V/12-V rails and battery inputs down to 3 V with UVLO margin |
| Feedback Reference | 0.8 V ±2% - sets output voltage accuracy via R1/R2 divider; enables 0.8-V minimum output |
| NMOS RDS(ON) | 250 mΩ (typ) - limits conduction loss at 1.5-A load; contributes to >90% efficiency at 12-VIN/3.3-VOUT |
| Shutdown Current | 400 nA (typ) - ensures ultra-low system standby power in battery-powered USB devices |
| Thermal Shutdown | 165°C (trip), 150°C (recovery) - protects against sustained overload or poor PCB thermal design |
Pinout & Package
LM2738XSDX/NOPB is housed in an 8-pin WSON package (3.0 mm × 3.0 mm, 0.65-mm pitch) with exposed thermal pad (DAP) connected to GND for enhanced heat dissipation. Package meets JEDEC MO-229 standard and supports reflow per J-STD-020.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 - BOOST | Bootstrap supply input | Drives NMOS gate during high-side conduction; requires external 0.1-µF X7R capacitor to SW |
| 2 - VIN | Main power input | Supplies power stage; must be bypassed with ≥10-µF ceramic capacitor near pin |
| 3 - VCC | Internal regulator input | Tied internally to VIN; shares same bypass requirement; not externally accessible |
| 4 - EN | Enable control | Logic-high (>1.4 V) enables operation; logic-low (<0.4 V) enters 400-nA shutdown mode |
| 5,7 - GND | Signal and power ground | Return path for feedback network and power stage; connects to exposed thermal pad (DAP) |
| 6 - FB | Voltage feedback input | Monitors output via resistor divider; regulates VOUT = 0.8 V × (1 + R1/R2) |
| 8 - SW | Switch node output | Connects to inductor and catch diode anode; swings from ~0 V to VIN during operation |
Key Features
| Feature | Design Value |
|---|---|
| Fixed 1.6-MHz switching | Enables compact 2.2-µH inductor and 22-µF ceramic output capacitor in typical 5-V-to-1.5-V designs |
| Internal soft-start | 600-µs reference ramp prevents in-rush current and output overshoot during power-up |
| Output overvoltage protection | Shuts off NMOS switch when FB exceeds 0.928 V (16% above 0.8-V reference), protecting downstream loads |
| Cycle-by-cycle current limit | Clamps peak switch current at 2.9 A (typ), preventing damage during short-circuit or startup overload |
| Thermal shutdown with hysteresis | Disables switching at 165°C junction temperature; resumes only after cooling to ~150°C, avoiding thermal oscillation |
Applications
| Local Point-of-Load Regulation | Core Power in HDDs |
|---|---|
Use Scenario: Regulating 1.5-V or 1.8-V core voltage from 5-V or 12-V backplane in embedded storage controllers. IC Role / Device Role / Timing Role: Primary buck converter providing tightly regulated, low-noise core supply with fast transient response. Use Value: 1.6-MHz operation minimizes output ripple and enables small 2.2-µH inductors, reducing PCB area by >40% vs. lower-frequency alternatives. | Use Scenario: Supplying 3.3-V logic and 1.2-V servo motor driver in 2.5-inch hard disk drives with strict size constraints. IC Role / Device Role / Timing Role: High-efficiency step-down regulator delivering 1.5-A continuous current with <100-µs load transient recovery. Use Value: 250-mΩ RDS(ON) and internal compensation reduce component count to just 6 external parts (inductor, diode, BOOST cap, input/output caps, feedback resistors). |
| DSL Modems | USB-Powered Devices |
Use Scenario: Generating 3.3-V and 1.8-V rails from 12-V adapter input in residential broadband gateways. IC Role / Device Role / Timing Role: Dual-rail power management IC supporting isolated analog and digital sections with independent enable control. Use Value: 400-nA shutdown current extends standby time during deep-sleep modes mandated by TR-111 energy standards. | Use Scenario: Converting 5-V USB power to 1.5-V or 3.3-V for portable media players, Bluetooth headsets, or USB-C accessories. IC Role / Device Role / Timing Role: Single-chip DC-DC solution meeting USB-IF voltage tolerance and ripple requirements without LDO post-regulation. Use Value: 0.8-V reference and 2% tolerance ensure output stays within ±3% of target across temperature, satisfying USB PD sink compliance. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar step-down regulator applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LM2738YSDX/NOPB | 550-kHz switching frequency, 95% max duty cycle, higher light-load efficiency at 12-VIN | Better suited for high-input-voltage, low-output-voltage designs where EMI filtering is critical | Select LM2738YSDX/NOPB when board layout allows larger inductors and lower-frequency operation improves conducted EMI compliance |
| TPS5430DDAR | 3-A output, 500-kHz fixed frequency, integrated high-side FET, no external BOOST diode required | Supports higher current loads but requires larger PCB area and lacks 1.6-MHz option for ultra-compact designs | Choose TPS5430DDAR when system load exceeds 1.5 A or when eliminating the BOOST diode simplifies BOM and layout verification |
Compared with LM2738YSDX/NOPB, the LM2738XSDX/NOPB trades lower light-load efficiency for significantly smaller magnetics and reduced footprint; versus TPS5430DDAR, it offers superior power density at 1.5-A loads but requires careful BOOST circuit design and external diode placement.
Availability
LM2738XSDX/NOPB is available at Aetrix Electronics and suitable for local point-of-load regulation, core power in HDDs, and USB-powered devices requiring stable component supply, long-term manufacturability, and TI-qualified automotive-grade traceability.
Supply support for LM2738XSDX/NOPB 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 over 50 years of innovation in high-reliability power conversion solutions.
The LM2738 product line delivers compact, high-frequency buck regulators optimized for space-constrained consumer, computing, and communications equipment where minimal external component count and fast transient response are critical.
FAQ
What is the exact switching frequency of LM2738XSDX/NOPB and how is it set?
The LM2738XSDX/NOPB has a factory-trimmed fixed switching frequency of 1.6 MHz, specific to the 'X' variant designation. This frequency is internally generated by a precision oscillator and cannot be adjusted externally. It is confirmed in the Electrical Characteristics table (FSW = 1.28–1.92 MHz, typ 1.6 MHz) and distinguishes LM2738XSDX/NOPB from the 550-kHz LM2738Y variant. The LM2738XSDX/NOPB achieves this high frequency using TI's 0.5-µm BiCMOS process, enabling smaller passive components without sacrificing regulation stability.
Does LM2738XSDX/NOPB require an external bootstrap diode, and why?
Yes, LM2738XSDX/NOPB requires an external Schottky diode (e.g., BAT54WS) between VIN and the BOOST pin to charge the external BOOST capacitor. This diode enables bootstrapping: during the SW low phase, VIN charges CBOOST through D2; during the SW high phase, CBOOST supplies gate drive to the NMOS switch. Without it, the internal switch cannot turn on fully, causing excessive RDS(ON) loss and potential thermal shutdown. The LM2738XSDX/NOPB datasheet explicitly specifies this in Figure 26 and Section 7.3.1.
What is the maximum output voltage achievable with LM2738XSDX/NOPB?
The LM2738XSDX/NOPB supports an output voltage range of 0.8 V to 18 V, as specified in the Features section and Recommended Operating Conditions table. This is achieved using the FB pin with an external resistor divider where VOUT = 0.8 V × (1 + R1/R2). At VIN = 20 V, the 18-V upper limit ensures safe operation within the absolute maximum SW voltage rating (24 V) and maintains sufficient headroom for the internal NMOS switch. Output voltages above 12 V require careful attention to BOOST voltage generation and thermal management.
How does the current limit function in LM2738XSDX/NOPB during overload conditions?
The LM2738XSDX/NOPB employs cycle-by-cycle current limiting that monitors switch current via an internal sense amplifier. When sensed current exceeds 2.9 A (typical), the NMOS switch is immediately turned off for that cycle, preventing damage during short circuits or heavy transient loads. This is distinct from hiccup or foldback modes - the device continues switching at full frequency but clamps peak current each cycle. The current limit is confirmed in Section 7.3.5 and Electrical Characteristics (ICL = 2 A min, 2.9 A typ), and remains active across the full operating temperature range (–40°C to +125°C).
Can LM2738XSDX/NOPB operate with a 3.3-V input, and what are the limitations?
Yes, LM2738XSDX/NOPB supports a minimum input voltage of 3 V per Recommended Operating Conditions. However, at 3.3-VIN, the maximum achievable output is limited by the minimum dropout condition: VOUT ≤ VIN – (IOUT × RDS(ON)) ≈ 3.3 V – (1.5 A × 0.25 Ω) = 2.925 V. Additionally, BOOST voltage generation becomes marginal - VBOOST–VSW must remain ≥2.5 V, so VIN-derived BOOST requires careful diode selection (low VF) and capacitor sizing. Efficiency drops below 80% in this region, as shown in Figure 13 (line regulation curves).
LM2738XSDX/NOPB Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- -
- Package/Case:
- 8-WFDFN Exposed Pad
- 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):
- 3V
- Voltage - Input (Max):
- 20V
- Voltage - Output (Min/Fixed):
- 0.8V
- Voltage - Output (Max):
- 18V
- Current - Output:
- 1.5A
- Frequency - Switching:
- 1.6MHz
- Synchronous Rectifier:
- No
- Operating Temperature:
- -40°C ~ 125°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 8-WSON (3x3)
LM2738XSDX/NOPB FAQ
1.How can I place an order for LM2738XSDX/NOPB through Aetrix?
Please submit a Request for Quotation (RFQ) for LM2738XSDX/NOPB 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 LM2738XSDX/NOPB reliable?
The price and inventory of LM2738XSDX/NOPB are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LM2738XSDX/NOPB is usually 5 days.
3.What payment methods are accepted for LM2738XSDX/NOPB?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LM2738XSDX/NOPB transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LM2738XSDX/NOPB?
LM2738XSDX/NOPB orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LM2738XSDX/NOPB 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 LM2738XSDX/NOPB?
For technical support, including LM2738XSDX/NOPB datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LM2738XSDX/NOPB requirements.
6.How does Aetrix verify that LM2738XSDX/NOPB is sourced from the original manufacturer or authorized distributors?
All LM2738XSDX/NOPB 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 LM2738XSDX/NOPB meets industry standards.
7.What is the process for return or replacement of LM2738XSDX/NOPB?
All LM2738XSDX/NOPB units undergo pre-shipment inspection (PSI). If there is an issue with LM2738XSDX/NOPB, 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 LM2738XSDX/NOPB part is unused and in its original packaging.
Return procedure for LM2738XSDX/NOPB:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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