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Texas Instruments LM34914SD
- Part No.:
- LM34914SD
- Manufacturer:
- Texas Instruments
- Package:
- 10-WFDFN Exposed Pad
- Datasheet:
-
LM34914SD.pdf
- Description:
- IC REG BUCK ADJ 1.25A 10WSON
- Quantity:
- Payment:
- Shipping:
Inventory:2,253
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Product details
Overview
LM34914SD from Texas Instruments is a high-voltage, valley-current-mode synchronous buck controller IC with integrated 44V N-channel MOSFET switch, delivering up to 1.25A continuous output current. It operates from 8V to 40V input, features programmable on-time control via RON/SD pin, no external loop compensation required, and delivers ultra-fast transient response in a thermally enhanced 3 mm × 3 mm WSON-10 package - used in industrial point-of-load (POL) and secondary post-regulation systems.
For engineers reviewing the LM34914SD datasheet, LM34914SD pinout, LM34914SD application, or LM34914SD equivalent, key selection considerations include its VIN range (8–40V), valley current limit behavior vs. VFB/VIN, 1.3 MHz max switching frequency, thermal shutdown at 175°C, and soft-start programmability - all critical for high-reliability DC/DC conversion in constrained layouts.
Technical Context
The LM34914SD employs a constant on-time (COT) control architecture where tON scales inversely with VIN to maintain near-constant switching frequency across line and load variations. Its valley current limit threshold dynamically adjusts with both VIN and FB voltage, enabling smooth transition into constant-current mode during overload without foldback.
Internal circuitry includes a 7.0V startup regulator (VCC), gate-drive UVLO (4.2V BST–SW threshold), 2.5V precision reference, overvoltage protection at 2.9V on FB, and cycle-by-cycle current limiting with ~50% on-time reduction when triggered - all implemented without external compensation components.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 8.0V to 40V - supports wide industrial and automotive supply rails without pre-regulation. |
| Output Current Capability | 1.25A continuous - verified at TJ ≤ 125°C with proper PCB thermal design and 3 mm × 3 mm WSON-10 exposed pad grounding. |
| Switching Frequency | Up to 1.3 MHz - enables compact magnetics and low-profile filter design; remains stable across load and input variation due to COT control. |
| Current Limit Threshold | 0.9A to 1.4A (VIN/VFB dependent) - valley-sense scheme prevents inductor saturation under high-VIN/high-load conditions. |
| Feedback Reference Voltage | 2.50V ±20 mV - sets regulated output via resistor divider; overvoltage comparator triggers at 2.9V for fast fault response. |
| Thermal Shutdown | 175°C activation with 20°C hysteresis - protects against sustained overload or poor heatsinking without latch-up. |
| Soft-Start Control | Internally sourced 12.5 µA current charges external SS capacitor to 2.5V - ensures controlled VOUT ramp and limits inrush. |
Pinout & Package
LM34914SD is housed in a thermally enhanced 10-pin WSON package (3 mm × 3 mm) with an exposed thermal pad (EP) that must be soldered to PCB ground plane for reliable thermal performance. Pin numbering follows standard top-side view with Pin 1 at bottom-left corner.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 SW | Switching Node | Connects to inductor, freewheeling diode cathode, and BST capacitor - carries high dv/dt and peak switch current. |
| 2 BST | Bootstrap Supply | Drives high-side gate via 0.022 µF capacitor to SW; recharged each off-time through internal diode from VCC. |
| 3 ISEN | Valley Current Sense Input | Senses recirculating inductor current during off-time; determines current limit threshold based on VIN and VFB. |
| 4 SGND | Sense Ground Return | Return path for current-sense resistor; separate from RTN to avoid noise coupling into regulation loop. |
| 5 RTN | Circuit Ground Reference | Ground reference for internal comparators, regulators, and logic - connects to system ground near power return paths. |
| 6 FB | Feedback Input | Compares output voltage (via resistor divider) to 2.5V reference; also monitors overvoltage (2.9V trip). |
| 7 SS | Soft-Start Capacitor Terminal | Charged by internal 12.5 µA current source to 2.5V - controls VOUT ramp rate and startup inrush. |
| 8 RON/SD | On-Time Programming / Shutdown | Resistor-to-VIN sets tON; grounding disables regulator and discharges SS capacitor. |
| 9 VCC | Startup Regulator Output | 7.0V regulated supply for internal circuits; can be externally biased (8–14V) to reduce dissipation. |
| 10 VIN | Main Input Supply | Accepts 8–40V; powers internal circuits via VCC regulator and drives buck switch directly. |
| EP | Exposed Thermal Pad | Internally connected to substrate; must be soldered to PCB ground plane with ≥4 thermal vias for θJA = 30°C/W. |
Key Features
| Feature | Design Value |
|---|---|
| No loop compensation required | Constant on-time control eliminates need for external RC network - simplifies layout and improves transient response. |
| Valley current limit with VIN/VFB scaling | Prevents inductor saturation under high-line/high-load by lowering limit threshold as VIN rises or VOUT drops. |
| Programmable soft-start | External capacitor on SS pin sets precise VOUT ramp time - avoids overshoot and reduces stress on downstream components. |
| Integrated 44V N-channel buck switch | RDS(on) = 0.33Ω (typ) enables high-efficiency conversion without external MOSFET or driver complexity. |
| Ultra-fast transient response | Regulation loop reacts within 150 ns of load step - maintains tight VOUT regulation during dynamic CPU or FPGA load changes. |
Applications
| Industrial Point-of-Load (POL) | Automotive Secondary Post-Regulator |
|---|---|
|
Use Scenario: Powering FPGA I/O banks or microcontroller peripherals from a 24V vehicle bus or factory 24/48V rail. IC Role / Device Role / Timing Role: Primary buck regulator providing tightly regulated 3.3V or 5V with fast load-step response and robust overcurrent protection. Use Value: Eliminates need for external compensation and reduces BOM count while maintaining <±1% output accuracy across -40°C to +125°C. |
Use Scenario: Stepping down 12V/24V battery-derived supply to 5V for infotainment display controllers or ADAS sensor interfaces. IC Role / Device Role / Timing Role: High-input-voltage buck controller with valley current limiting to survive cold-crank transients and load dumps. Use Value: Dynamic current limit adjustment prevents false trips during battery voltage sag while sustaining >1.25A output. |
| High-Voltage Industrial Sensor Hub | Telecom Line Card Bias Supply |
|
Use Scenario: Providing isolated 3.3V bias to multiple analog front-end sensors powered from a 36V industrial fieldbus. IC Role / Device Role / Timing Role: Compact, thermally efficient POL regulator operating continuously at full load in confined enclosures. Use Value: Exposed thermal pad and 3×3 mm footprint enable >1.25A delivery in space-constrained modules without forced air cooling. |
Use Scenario: Generating 3.3V/5V auxiliary supplies from 48V telecom central office distribution rails. IC Role / Device Role / Timing Role: High-reliability buck converter with thermal shutdown and VCC UVLO for unattended operation. Use Value: 175°C thermal shutdown with 20°C hysteresis ensures graceful recovery after temporary overheating events. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar buck regulator applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LM5164QWRXMRQ1 | Wider VIN range (4.5–100V), higher 1.5A output, but requires external MOSFETs and loop compensation. | Better suited for 48V telecom or HEV battery systems needing >40V input; less integrated than LM34914SD. | Select when input exceeds 40V or when higher output current with external FET flexibility is needed. |
| TPS54240DGQR | Adjustable frequency (100kHz–2.5MHz), integrated compensation, but only 2.5A max and 36V max VIN. | Preferred for designs requiring EMI-controlled spread-spectrum or tighter output tolerance (<±0.5%). | Choose if frequency tuning or lower output ripple is prioritized over ultra-small footprint and zero-compensation simplicity. |
Compared with LM5164QWRXMRQ1 and TPS54240DGQR, the LM34914SD offers the smallest solution size (no external FETs or compensation), fastest transient response (no loop tuning), and most direct implementation for 8–40V inputs delivering ≤1.25A - ideal for space- and time-constrained industrial and automotive POL designs.
Availability
LM34914SD is available at Aetrix Electronics and suitable for industrial point-of-load (POL) regulation, automotive secondary post-regulation, and high-voltage sensor hub power management requiring stable component supply, long-term lifecycle support, and traceable sourcing.
Supply support for LM34914SD 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 ICs, with decades of expertise in high-reliability power conversion solutions.
The LM34914SD belongs to TI's high-voltage buck regulator product line, designed specifically for compact, high-efficiency DC/DC conversion in industrial automation, automotive subsystems, and telecom infrastructure where input voltages exceed 24V.
FAQ
What is the maximum allowable input voltage for the LM34914SD?
The LM34914SD has an absolute maximum VIN rating of 44V, but its specified operating input voltage range is 8.0V to 40V. Exceeding 40V may trigger internal protection or degrade reliability. The device integrates a 44V N-channel buck switch, and the BST pin withstands up to 52V - however, sustained operation above 40V is not characterized or guaranteed per the SNVS453B datasheet.
How does the LM34914SD implement current limiting without external sense resistors?
The LM34914SD uses internal valley current sensing via the ISEN pin, which monitors recirculating inductor current during the off-time. The current limit threshold varies with VIN and FB voltage - for example, it ranges from 0.9A to 1.4A depending on operating conditions - eliminating the need for external sense resistors while preventing inductor saturation under high-line/high-load scenarios.
Can the LM34914SD operate without an external bootstrap capacitor?
No - the LM34914SD requires a 0.022 µF ceramic capacitor between BST and SW pins to supply gate drive voltage for the internal N-channel MOSFET. Without this capacitor, the high-side gate cannot be properly charged, resulting in failure to switch and no output regulation. The BST capacitor is recharged each off-time through an internal diode from VCC.
What is the purpose of the SGND and RTN pins being separate on the LM34914SD?
SGND provides a dedicated low-noise return path for the current-sense amplifier, isolating it from power-ground noise on RTN. This separation prevents switching transients from corrupting valley current measurement - ensuring accurate, stable current limiting and regulation. RTN serves as the reference for all other internal circuits including FB, VCC, and logic.
Does the LM34914SD support adjustable switching frequency, and how is it set?
Yes - the LM34914SD's switching frequency is programmable via an external resistor (RON) connected between VIN and the RON/SD pin. For example, a 200 kΩ resistor yields ~275 kHz at VIN = 12V. The on-time formula tON = (VIN − 1.5) / (1.15 × 10⁻¹⁰ × (RON + 1.4k)) + 50 ns defines the relationship, enabling predictable frequency selection across input voltage range.
LM34914SD Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- -
- Package/Case:
- 10-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):
- 8V
- Voltage - Input (Max):
- 40V
- Voltage - Output (Min/Fixed):
- 2.5V
- Voltage - Output (Max):
- 37V
- Current - Output:
- 1.25A
- Frequency - Switching:
- 1.3MHz
- Synchronous Rectifier:
- No
- Operating Temperature:
- -40°C ~ 125°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 10-WSON (3x3)
LM34914SD FAQ
1.How can I place an order for LM34914SD through Aetrix?
Please submit a Request for Quotation (RFQ) for LM34914SD 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 LM34914SD reliable?
The price and inventory of LM34914SD are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LM34914SD is usually 5 days.
3.What payment methods are accepted for LM34914SD?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LM34914SD transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LM34914SD?
LM34914SD orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LM34914SD 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 LM34914SD?
For technical support, including LM34914SD datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LM34914SD requirements.
6.How does Aetrix verify that LM34914SD is sourced from the original manufacturer or authorized distributors?
All LM34914SD 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 LM34914SD meets industry standards.
7.What is the process for return or replacement of LM34914SD?
All LM34914SD units undergo pre-shipment inspection (PSI). If there is an issue with LM34914SD, 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 LM34914SD part is unused and in its original packaging.
Return procedure for LM34914SD:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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