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Texas Instruments LM34926MRX/NOPB
- Part No.:
- LM34926MRX/NOPB
- Manufacturer:
- Texas Instruments
- Package:
- 8-PowerSOIC (0.154", 3.90mm Width)
- Datasheet:
-
LM34926MRX/NOPB.pdf
- Description:
- IC REG BUCK ADJ 300MA 8SOPWR
- Quantity:
- Payment:
- Shipping:
Inventory:2,811
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Product details
Overview
LM34926MRX/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, 7.5–100 V input range, 1.225 V precision feedback reference, and operation up to 1 MHz. It enables compact, low-component-count isolated bias supplies in telecom and industrial fly-buck topologies.
For engineers reviewing the LM34926MRX/NOPB datasheet, LM34926MRX/NOPB pinout, LM34926MRX/NOPB application, or LM34926MRX/NOPB equivalent, key selection criteria include input voltage range compatibility, COT-based transient response behavior, bootstrap gate drive requirements, UVLO programmability, and thermal performance in WSON-8 packaging.
Technical Context
The LM34926MRX/NOPB implements a constant on-time (COT) control architecture where switch on-time is inversely proportional to VIN and set by an external RON resistor - enabling near-constant switching frequency across 7.5–100 V input. Regulation relies on direct comparison of FB voltage to a 1.225 V internal reference, with overvoltage shutdown at 1.62 V.
It integrates a self-biased 7.6 V VCC regulator (with 4.5 V UVLO), intelligent peak current limiting (575 mA typ), thermal shutdown at 165°C, and dual-level UVLO via the UVLO pin (0.66 V shutdown, 1.225 V enable). The synchronous rectifier operates without diode emulation, maintaining continuous conduction mode across load conditions.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 7.5 V to 100 V - supports direct connection to 48 V telecom, 24/36 V automotive, and industrial HV rails without pre-regulation. |
| Feedback Reference | 1.225 V ±2% - sets output voltage via external resistor divider; enables precise regulation independent of line/load variation. |
| Switching Frequency | Up to 1 MHz - adjustable via RON; stable operation maintained across input and load changes due to COT architecture. |
| Buck Switch RDS(on) | 0.8–1.8 Ω - low conduction loss at 200 mA test current; optimized for efficiency in isolated bias applications. |
| Synchronous Rectifier RDS(on) | 0.45–1.0 Ω - eliminates Schottky diode, reducing heat and component count in secondary-side regulation. |
| Current Limit Threshold | 390–750 mA - peak-limited protection with adaptive off-time scaling based on FB voltage and VIN. |
| VCC Regulator Output | 7.6 V (6.25–8.55 V) - powers internal gate drivers and logic; disables when externally supplied 8.55–13 V applied. |
Pinout & Package
LM34926MRX/NOPB is packaged in an 8-pin WSON (NGU) package with 4.00 mm × 4.00 mm body size and exposed thermal pad connected to RTN.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 RTN | Ground reference | System ground return for all internal circuits; exposed pad must be soldered to PCB ground plane for thermal management. |
| 2 VIN | Main power input | Accepts 7.5–100 V; powers VCC regulator and high-voltage gate drivers; requires local 10 µF ceramic input capacitor. |
| 3 UVLO | Undervoltage lockout control | Programmable enable/disable threshold (0.66 V shutdown, 1.225 V start); hysteresis enabled via internal 20 µA current source. |
| 4 RON | On-time programming | Resistor-to-VIN sets minimum on-time; ensures >100 ns at max VIN for stable COT operation and frequency control. |
| 5 FB | Feedback input | Compares output-derived voltage to 1.225 V reference; requires ≥25 mV ripple for stable COT regulation. |
| 6 VCC | Internal bias supply output | 7.6 V regulated output powering gate drivers; requires 1.0 µF decoupling; UVLO at 4.5 V disables IC if undervolted. |
| 7 BST | Bootstrap supply node | Charged via internal diode from VCC during SW low phase; requires 0.01 µF ceramic capacitor to SW for high-side gate drive. |
| 8 SW | Power switching node | Drives external inductor; connects to BST capacitor; withstands VIN + 0.3 V transient; critical for EMI and layout integrity. |
Key Features
| Feature | Design Value |
|---|---|
| No loop compensation required | COT control eliminates need for external compensation network - reduces BOM count and design iteration time. |
| Integrated high- and low-side switches | Dual 100-V N-channel MOSFETs eliminate external FETs and driver ICs - simplifies isolated bias supply implementation. |
| No Schottky diode needed | Synchronous rectification replaces lossy external diode - improves efficiency and thermal performance at light loads. |
| Adjustable UVLO and shutdown | UVLO pin allows user-defined startup voltage and remote shutdown - enables sequencing and brownout protection in multi-rail systems. |
| Ultra-fast transient response | COT architecture provides immediate on-time adjustment to load steps - maintains tight output regulation without complex compensation. |
Applications
| Isolated Telecom Bias Supply | Automotive Isolated Auxiliary Rail |
|---|---|
Use Scenario: Generating a stable 10 V/100 mA auxiliary bias rail from a 48 V telecom bus using a fly-buck transformer configuration. IC Role / Device Role / Timing Role: Secondary-side controller regulating isolated output via COT feedback; manages synchronous rectification and bootstrap timing. Use Value: Eliminates optocoupler and TL431 feedback loop; achieves <1% output deviation under 50–100% load step with no compensation components. | Use Scenario: Powering isolated CAN transceiver and microcontroller peripherals from a 24 V vehicle battery in ADAS domain controllers. IC Role / Device Role / Timing Role: High-voltage secondary-side regulator providing clean, isolated 5 V/200 mA rail; handles cold-crank (6.5 V) to load-dump (40 V) transients via programmable UVLO. Use Value: Enables single-transformer dual-output design (e.g., 5 V + 3.3 V) while maintaining <150 mV output droop during 100 mA load steps. |
| Industrial Isolated Sensor Interface | Medical Equipment Auxiliary Power |
Use Scenario: Delivering galvanically isolated 3.3 V power to analog front-end sensors in PLC I/O modules operating from 24–48 V field buses. IC Role / Device Role / Timing Role: Secondary-side bias regulator implementing fly-buck topology; uses COT control to maintain regulation during rapid sensor sampling bursts. Use Value: Achieves <2% output error over –40°C to +125°C junction temperature; thermal shutdown prevents fault propagation during overtemperature events. | Use Scenario: Providing reinforced-isolation 12 V/50 mA bias for isolated ADCs and digital isolators in patient-connected monitoring equipment. IC Role / Device Role / Timing Role: Safety-critical secondary-side regulator with dual UVLO thresholds and thermal shutdown - ensures fail-safe disable under fault conditions. Use Value: Meets IEC 60601 creepage/clearance requirements via transformer isolation; 165°C thermal shutdown prevents hazardous overheating. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar isolated secondary-side bias regulator applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LM5160QPWPRQ1 | Wide-input (3–65 V) primary-side synchronous buck with integrated 100-V FET; requires optocoupler feedback for isolation. | Requires external isolation feedback path; less suitable for compact secondary-side-only designs. | Prefer when primary-side regulation and higher output current (>500 mA) are needed. |
| UCC28740DR | PSR flyback controller with quasi-resonant operation; no secondary-side sensing; 9–30 V VDD range. | Lacks integrated secondary-side switches; needs external MOSFETs and transformer auxiliary winding for bias. | Prefer for cost-sensitive, lower-power (<10 W) isolated supplies where BOM count is prioritized over layout simplicity. |
Compared with LM5160QPWPRQ1 and UCC28740DR, the LM34926MRX/NOPB uniquely integrates both high- and low-side switches on the secondary side, eliminating optocouplers, external FETs, and compensation networks - delivering the lowest component count and fastest transient response for fixed-output isolated bias rails up to 100 V input.
Availability
LM34926MRX/NOPB is available at Aetrix Electronics and suitable for isolated telecom bias supply, automotive auxiliary rail generation, and industrial sensor interface applications requiring stable component supply, long-term lifecycle support, and traceable sourcing.
Supply support for LM34926MRX/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 industrial and automotive power solutions.
The LM34926MRX/NOPB belongs to TI's isolated DC-DC bias regulator product line, designed specifically to simplify secondary-side power delivery in fly-buck and isolated buck-derived topologies while minimizing component count and layout complexity.
FAQ
What is the recommended minimum on-time for stable operation of the LM34926MRX/NOPB?
The LM34926MRX/NOPB requires a minimum on-time greater than 100 ns at maximum input voltage (100 V) to ensure reliable COT control. This is achieved by selecting the RON resistor per the TON = K × RON/VIN equation - for example, 250 kΩ at 100 V yields ~370 ns typical on-time. Using smaller RON values risks cycle skipping or instability.
Can the LM34926MRX/NOPB operate without an external bootstrap capacitor?
No - the LM34926MRX/NOPB requires a 0.01 µF ceramic capacitor between BST and SW pins to sustain high-side gate drive. Without it, the bootstrap voltage collapses after the first switching cycle, disabling the buck switch. The internal diode charges this capacitor only when SW is low, making the capacitor essential for continuous operation.
How does the LM34926MRX/NOPB handle short-circuit protection?
The LM34926MRX/NOPB implements intelligent peak current limiting: if inductor current exceeds 575 mA (typ), the on-time terminates immediately and a non-resettable off-timer activates. Off-time scales with FB voltage - e.g., 16 µs at FB = 0 V (short circuit) versus shorter durations at higher FB - enabling safe, foldback-free recovery without latch-off.
Is the LM34926MRX/NOPB compatible with external VCC biasing?
Yes - applying 8.55–13 V to the VCC pin disables the internal 7.6 V regulator, reducing power dissipation at high VIN. This is especially beneficial in 48–100 V applications where internal VCC regulation would dissipate >300 mW. External bias must be well-regulated and bypassed with ≥1 µF capacitance.
What is the purpose of the 25 mV ripple requirement at the FB pin of the LM34926MRX/NOPB?
The LM34926MRX/NOPB's COT control requires ≥25 mV of monotonic resistive ripple at FB to reliably detect the end of off-time and trigger the next on-pulse. Capacitive ripple alone is insufficient because it lacks phase alignment with inductor current; adding RC series resistance to the feedback divider ensures stable regulation and prevents burst-mode oscillation.
LM34926MRX/NOPB Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- -
- Package/Case:
- 8-PowerSOIC (0.154", 3.90mm Width)
- 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-SO PowerPad
LM34926MRX/NOPB FAQ
1.How can I place an order for LM34926MRX/NOPB through Aetrix?
Please submit a Request for Quotation (RFQ) for LM34926MRX/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 LM34926MRX/NOPB reliable?
The price and inventory of LM34926MRX/NOPB are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LM34926MRX/NOPB is usually 5 days.
3.What payment methods are accepted for LM34926MRX/NOPB?
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4.How is shipping managed for LM34926MRX/NOPB?
LM34926MRX/NOPB orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LM34926MRX/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 LM34926MRX/NOPB?
For technical support, including LM34926MRX/NOPB datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LM34926MRX/NOPB requirements.
6.How does Aetrix verify that LM34926MRX/NOPB is sourced from the original manufacturer or authorized distributors?
All LM34926MRX/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 LM34926MRX/NOPB meets industry standards.
7.What is the process for return or replacement of LM34926MRX/NOPB?
All LM34926MRX/NOPB units undergo pre-shipment inspection (PSI). If there is an issue with LM34926MRX/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 LM34926MRX/NOPB part is unused and in its original packaging.
Return procedure for LM34926MRX/NOPB:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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