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Texas Instruments LM34926SD/NOPB
- Part No.:
- LM34926SD/NOPB
- Manufacturer:
- Texas Instruments
- Package:
- 8-WDFN Exposed Pad
- Datasheet:
-
LM34926SD/NOPB.pdf
- Description:
- IC REG BUCK ADJ 300MA 8WSON
- Quantity:
- Payment:
- Shipping:
Inventory:2,579
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Product details
Overview
LM34926SD/NOPB from Texas Instruments is a high-voltage integrated secondary-side bias regulator for isolated DC-DC converters, featuring dual 100-V N-channel MOSFET switches (high-side buck and low-side synchronous), constant on-time (COT) control, and 7.5 V to 100 V input range. It delivers regulated output voltage adjustable from 1.225 V via external resistors, supports up to 1 MHz switching frequency, and targets isolated telecom and industrial bias supply applications.
For engineers reviewing the LM34926SD/NOPB datasheet, LM34926SD/NOPB pinout, LM34926SD/NOPB application, or LM34926SD/NOPB equivalent, key selection considerations include its integrated 300-mA high-side/low-side switches, programmable UVLO threshold, 1.225 V ±2% feedback reference, thermal shutdown at 165°C, and WSON-8 package with exposed thermal pad.
Technical Context
The LM34926SD/NOPB implements a constant on-time (COT) control architecture where on-time is inversely proportional to VIN and set by an external RON resistor, enabling near-constant operating frequency across input voltage variations. Its regulation relies on comparing FB voltage to a precision 1.225 V internal reference, with overvoltage protection triggered at 1.62 V.
It integrates a self-biased 7.6 V VCC regulator (with 4.5 V UVLO), bootstrap gate drive for the high-side switch (requiring 0.01 µF BST–SW capacitor), and intelligent peak current limiting (575 mA typical) with off-time scaling based on FB voltage and VIN - ensuring robust short-circuit protection without external compensation.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 7.5 V to 100 V - enables direct connection to 48 V telecom or automotive bus without pre-regulation. |
| Feedback Reference | 1.225 V ±2% - sets precise output voltage via RFB1/RFB2 divider; determines regulation accuracy. |
| Buck Switch RDS(ON) | 0.8 Ω (typ) - limits conduction loss in high-side FET at 200 mA test current. |
| Synchronous Rectifier RDS(ON) | 0.45 Ω (typ) - replaces Schottky diode, improving efficiency and eliminating need for external rectifier. |
| Current Limit Threshold | 575 mA (typ) - peak-limited protection; initiates intelligent off-time scaling to maintain safe operation during overload. |
| VCC Regulator Output | 7.6 V (typ), 6.25–8.55 V range - powers internal gate drivers and logic; disables when externally supplied 8.55–13 V applied. |
| Thermal Shutdown | 165°C (typ), 20°C hysteresis - forces reset state to prevent junction damage; resumes at ~145°C. |
Pinout & Package
LM34926SD/NOPB is housed in an 8-pin WSON package (4.00 mm × 4.00 mm) with exposed thermal pad (EP) electrically and thermally connected to RTN. The EP must be soldered to PCB ground plane for optimal thermal performance (RθJC(bot) = 3.2°C/W).
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 RTN | Ground reference | System ground return for all internal circuits; EP must connect here for thermal management. |
| 2 VIN | Main power input | Accepts 7.5–100 V; supplies VCC regulator and high-voltage gate drive circuitry. |
| 3 UVLO | Undervoltage detection input | Resistor divider from VIN sets startup threshold; <0.66 V forces shutdown; >1.225 V enables operation. |
| 4 RON | On-time programming | Resistor to VIN sets COT duration; minimum 100 ns required at max VIN for stable operation. |
| 5 FB | Feedback input | Compares to 1.225 V reference; ripple ≥25 mV required for stable COT regulation. |
| 6 VCC | Internal bias supply output | 7.6 V regulated output; powers gate drivers; requires 1.0 µF decoupling capacitor. |
| 7 BST | Bootstrap supply | Charged from VCC via internal diode during SW low phase; drives high-side gate. |
| 8 SW | Switching node | Connects to inductor and BST capacitor; carries full switching waveform; referenced to RTN. |
Key Features
| Feature | Design Value |
|---|---|
| No loop compensation required | COT control eliminates external compensation components, reducing BOM count and design iteration time. |
| Integrated high-side + low-side switches | Dual 100-V N-MOSFETs replace discrete FETs and driver ICs, simplifying isolated fly-buck topology implementation. |
| No Schottky diode needed | Synchronous rectification improves efficiency >3% at light loads and eliminates reverse recovery losses. |
| Adjustable UVLO with hysteresis | Programmable input undervoltage lockout using external resistor divider ensures clean startup and brownout immunity. |
| Ultra-fast transient response | COT architecture provides immediate on-time adjustment to load steps, minimizing output voltage deviation. |
Applications
| Isolated Telecom Bias Supply | Automotive Infotainment Power Rail |
|---|---|
Use Scenario: Generating isolated 5 V or 3.3 V auxiliary bias for PoE-powered Ethernet switches or base station RF modules. IC Role / Device Role / Timing Role: Secondary-side synchronous buck controller regulating transformer-coupled output; provides stable bias independent of primary-side regulation. Use Value: Eliminates external Schottky and reduces component count by 4+ parts while maintaining >85% efficiency at 100 mA load. | Use Scenario: Deriving isolated 12 V bias for CAN transceivers or display backlight drivers in 12 V/24 V vehicle systems. IC Role / Device Role / Timing Role: Fly-buck secondary regulator accepting wide-input (7.5–100 V) transients; operates continuously across cold-crank and load-dump conditions. Use Value: Withstands 100 V surge events and maintains regulation down to 7.5 V, enabling single-bias solution across 12 V and 24 V platforms. |
| Industrial PLC I/O Module Isolation | Medical Imaging Sensor Bias |
Use Scenario: Providing galvanically isolated 5 V/3.3 V power to analog input/output channels in programmable logic controllers. IC Role / Device Role / Timing Role: Secondary-side bias regulator in fly-buck configuration; delivers low-noise, ripple-controlled output for precision ADC/DAC references. Use Value: 1.225 V ±2% reference and COT stability ensure <10 mV output deviation under 10–90% load step, meeting IEC 61000-4-5 compliance margins. | Use Scenario: Powering isolated analog front-end sensors in MRI or ultrasound equipment requiring ultra-low EMI and high reliability. IC Role / Device Role / Timing Role: Secondary-side regulator with thermal shutdown (165°C) and no external diode, minimizing heat generation near sensitive detectors. Use Value: Synchronous rectification reduces thermal dissipation by ~150 mW vs. Schottky solution, lowering local temperature rise critical for sensor calibration stability. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar secondary-side bias regulator applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LM5165QDGSRQ1 | Wide-input (3–65 V) buck regulator with integrated 500-mA FET; lacks synchronous rectifier and secondary-side isolation optimization. | Designed for primary-side non-isolated regulation; requires external transformer driver for isolation. | Choose when designing non-isolated point-of-load or when secondary-side integration is not required. |
| UCC28740DR | Primary-side sensing flyback controller with quasi-resonant operation; no integrated secondary-side switches. | Requires external secondary rectifier and feedback optocoupler; higher system-level complexity. | Prefer for cost-sensitive, lower-power (<5 W) isolated supplies where transformer utilization efficiency is prioritized. |
Compared with LM5165QDGSRQ1 and UCC28740DR, the LM34926SD/NOPB uniquely integrates both high-side and low-side 100-V switches optimized for secondary-side fly-buck operation - delivering lower component count, faster transient response, and elimination of Schottky losses in isolated bias applications.
Availability
LM34926SD/NOPB is available at Aetrix Electronics and suitable for isolated telecom bias supply, automotive infotainment power rails, and industrial PLC I/O module isolation requiring stable component supply, long-term lifecycle support, and traceable sourcing.
Supply support for LM34926SD/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 company specializing in analog, embedded processing, and power management technologies, with leadership in high-reliability power conversion ICs.
The LM34926SD/NOPB belongs to TI's isolated bias regulator product line, engineered specifically for secondary-side implementation in fly-buck and isolated buck-derived topologies to simplify high-voltage isolation power design.
FAQ
What is the recommended minimum output capacitor ESR for stable operation of the LM34926SD/NOPB?
The LM34926SD/NOPB requires ≥25 mV of ripple voltage at the FB pin for stable constant on-time (COT) regulation. This mandates sufficient output capacitor ESR to generate resistive ripple in phase with inductor current. If ceramic capacitors with low ESR are used, a series RC network (RC ≥ 25 mV / ΔIL(MIN)) must be added between COUT and FB to meet this requirement - otherwise, multiple on-time bursts and instability occur.
Can the LM34926SD/NOPB operate without an external bootstrap capacitor?
No, the LM34926SD/NOPB requires a 0.01 µF ceramic capacitor between BST and SW pins. This capacitor supplies gate drive voltage to the high-side N-MOSFET during its on-time. During SW low phase, it recharges from the internal VCC regulator via an integrated diode. Omitting it causes gate drive failure and immediate functional loss.
How does the LM34926SD/NOPB implement undervoltage lockout (UVLO) control?
The LM34926SD/NOPB uses a dual-threshold UVLO circuit on the UVLO pin: below 0.66 V triggers shutdown mode (50–225 µA quiescent current); between 0.66 V and 1.225 V enables VCC regulator only (standby); above 1.225 V enables full regulation. Hysteresis is achieved via a 20 µA internal current source switched into the external resistor divider, ensuring clean turn-on/turn-off transitions.
What is the maximum achievable switching frequency of the LM34926SD/NOPB and what limits it?
The LM34926SD/NOPB supports up to 1 MHz switching frequency, but actual maximum is constrained by minimum on-time: at VIN = 100 V, RON must be selected so on-time ≥100 ns (per datasheet). For example, with RON = 250 kΩ, TON ≈ 500 ns at 100 V - limiting max frequency to ~2 MHz theoretical, but practical limit is ~1 MHz due to gate drive timing and layout constraints.
Does the LM34926SD/NOPB support discontinuous conduction mode (DCM) operation?
No, the LM34926SD/NOPB is designed to operate exclusively in continuous conduction mode (CCM) due to its synchronous rectifier architecture and lack of diode emulation. Even at light loads, the low-side N-MOSFET remains active, preventing inductor current reversal and ensuring monotonic FB ripple - a requirement for stable COT control.
LM34926SD/NOPB Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- -
- Package/Case:
- 8-WDFN Exposed Pad
- Packaging:
- Tape & Reel (TR)
- Product Status:
- Active
- Function:
- Step-Down
- Output Configuration:
- Positive, Isolation Capable
- Topology:
- Buck
- Output Type:
- Adjustable
- Number of Outputs:
- 1
- Voltage - Input (Min):
- 7.5V
- Voltage - Input (Max):
- 100V
- Voltage - Output (Min/Fixed):
- 1.225V
- Voltage - Output (Max):
- 100V
- Current - Output:
- 300mA
- Frequency - Switching:
- Adj to 1MHz
- Synchronous Rectifier:
- Yes
- Operating Temperature:
- -40°C ~ 125°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 8-WSON (4x4)
LM34926SD/NOPB FAQ
1.How can I place an order for LM34926SD/NOPB through Aetrix?
Please submit a Request for Quotation (RFQ) for LM34926SD/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 LM34926SD/NOPB reliable?
The price and inventory of LM34926SD/NOPB are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LM34926SD/NOPB is usually 5 days.
3.What payment methods are accepted for LM34926SD/NOPB?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LM34926SD/NOPB transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LM34926SD/NOPB?
LM34926SD/NOPB orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LM34926SD/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 LM34926SD/NOPB?
For technical support, including LM34926SD/NOPB datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LM34926SD/NOPB requirements.
6.How does Aetrix verify that LM34926SD/NOPB is sourced from the original manufacturer or authorized distributors?
All LM34926SD/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 LM34926SD/NOPB meets industry standards.
7.What is the process for return or replacement of LM34926SD/NOPB?
All LM34926SD/NOPB units undergo pre-shipment inspection (PSI). If there is an issue with LM34926SD/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 LM34926SD/NOPB part is unused and in its original packaging.
Return procedure for LM34926SD/NOPB:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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