My Inquiry
My Account
Texas Instruments LM34926SDX/NOPB
- Part No.:
- LM34926SDX/NOPB
- Manufacturer:
- Texas Instruments
- Package:
- 8-WDFN Exposed Pad
- Datasheet:
-
LM34926SDX/NOPB.pdf
- Description:
- IC REG BUCK ADJ 300MA 8WSON
- Quantity:
- Payment:
- Shipping:
Inventory:3,372
Please send an inquiry. Send us your inquiry, and we will respond immediately.
Product details
Overview
LM34926SDX/NOPB from Texas Instruments is a high-voltage, constant-on-time (COT) synchronous buck controller IC designed for isolated secondary-side bias regulation in fly-buck and transformer-coupled DC-DC converters. It integrates 100-V N-channel high-side and low-side switches, operates from 7.5 V to 100 V input, delivers up to 300 mA output current, features 1.225 V ±2% precision feedback reference, and supports adjustable switching frequency up to 1 MHz - enabling compact, low-component-count telecom and automotive auxiliary supplies.
For engineers reviewing the LM34926SDX/NOPB datasheet, LM34926SDX/NOPB pinout, LM34926SDX/NOPB application, or LM34926SDX/NOPB equivalent, key selection criteria include its integrated dual-MOSFET architecture, bootstrap-based gate drive, UVLO programmability via external resistor divider, COT control eliminating loop compensation, and thermal shutdown with 165°C trip point - all critical for robust isolated bias design under wide-input-voltage transients.
Technical Context
The LM34926SDX/NOPB implements a constant-on-time control scheme where on-time is inversely proportional to VIN and set by an external RON resistor, enabling near-constant operating frequency across 7.5–100 V input range. Its internal 7.6 V VCC regulator powers gate drivers and logic, with UVLO at 4.5 V and hysteresis of 300 mV.
It uses a precision 1.225 V feedback reference and overvoltage comparator (1.62 V threshold) to terminate on-time during fault conditions. Current limiting is peak-based (575 mA typical), with intelligent off-time scaling dependent on FB voltage and VIN - ensuring fast short-circuit response while minimizing foldback during moderate overloads.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 7.5 V to 100 V - supports direct connection to 48 V telecom, 24/48 V industrial, and 12–60 V automotive bus rails without pre-regulation. |
| Feedback Reference | 1.225 V ±2% - enables accurate output voltage setting (e.g., 5 V, 12 V, 15 V) using standard resistor dividers with minimal drift. |
| Switch RDS(on) | Buck switch: 0.8–1.8 Ω; Sync switch: 0.45–1.0 Ω - reduces conduction loss and improves efficiency at 300 mA load in WSON-8 package. |
| Current Limit Threshold | 390–750 mA - provides peak-current protection scalable with load and input conditions; triggers forced off-time for safe short-circuit handling. |
| VCC Regulator Output | 7.6 V (6.25–8.55 V) - self-biases internal circuitry and charges BST capacitor; disables when externally supplied 8.55–13 V applied. |
| Thermal Shutdown | 165°C trip, 145°C hysteresis - prevents permanent damage during sustained overload or poor PCB thermal design. |
| Operating Junction Temp | –40°C to +125°C - qualified for extended temperature operation in automotive under-hood and industrial control environments. |
Pinout & Package
LM34926SDX/NOPB is packaged in an 8-pin WSON (NGU) thermally enhanced exposed-pad package measuring 4.00 mm × 4.00 mm, with the EP pad electrically and thermally connected to RTN.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 RTN | Ground Reference | Primary GND return for internal circuits and exposed pad; must be solidly connected to system ground plane for thermal and EMI performance. |
| 2 VIN | Main Input Supply | High-voltage input node (7.5–100 V); connects directly to primary-side bus or transformer secondary rectified output. |
| 3 UVLO | Undervoltage Sense Input | Resistor-divider input to enable/disable operation; 0.66 V shutdown threshold and 1.225 V start-up threshold with internal hysteresis current source. |
| 4 RON | On-Time Programming | Resistor-to-VIN sets minimum on-time; determines switching frequency - e.g., 100 kΩ yields ~750 kHz at 48 V input. |
| 5 FB | Feedback Input | Inverting input of regulation comparator referenced to 1.225 V; requires ≥25 mV ripple for stable COT operation. |
| 6 VCC | Internal Bias Rail | 7.6 V regulated output powering gate drivers; requires 1.0 µF ceramic decoupling; UVLO at 4.5 V enables IC startup. |
| 7 BST | Bootstrap Supply | Charged via internal diode from VCC during SW low phase; supplies floating gate drive for high-side N-MOSFET. |
| 8 SW | Power Switch Node | Drain of integrated high-side MOSFET; connects to inductor, BST capacitor, and transformer secondary winding in fly-buck topology. |
Key Features
| Feature | Design Value |
|---|---|
| No Schottky required | Integrated synchronous rectifier eliminates external body-diode conduction loss and associated heat, reducing BOM count and improving light-load efficiency. |
| No loop compensation needed | COT architecture inherently stabilizes control loop without external compensation components - simplifies layout and accelerates design iteration. |
| Ultra-fast transient response | On-time retriggering based on FB falling below 1.225 V enables sub-microsecond recovery from load steps - critical for digital IC bias rails. |
| Adjustable UVLO | Programmable start-up and shutdown thresholds via external resistor divider on UVLO pin - allows custom brown-in/brown-out behavior for system-level sequencing. |
| Intelligent peak current limit | Off-time scales inversely with FB voltage - longer off-time during hard shorts (FB ≈ 0 V), shorter off-time during mild overloads - minimizes output droop and speeds recovery. |
Applications
| Isolated Telecom Bias Supply | Automotive Infotainment Power |
|---|---|
Use Scenario: Generating isolated 5 V or 12 V auxiliary bias for PoE-powered Ethernet PHYs, optical modules, or remote management controllers in telecom infrastructure. IC Role / Device Role / Timing Role: Secondary-side synchronous buck controller regulating transformer-coupled output; provides precise, ripple-sensitive feedback timing via COT control. Use Value: Eliminates need for optocoupler feedback or TL431 shunt regulator - reduces component count, improves reliability, and maintains tight regulation across –40°C to +85°C ambient. | Use Scenario: Providing isolated 3.3 V or 5 V supply for MCU, CAN transceiver, and display backlight driver in vehicle infotainment head units. IC Role / Device Role / Timing Role: Fly-buck secondary regulator deriving bias from main 12 V battery rail through coupled inductor; leverages COT for immunity to battery voltage sag during cranking. Use Value: Sustains regulation down to 7.5 V input - avoids system reset during cold-crank events; thermal shutdown protects against enclosure overheating in sealed dash-mount designs. |
| Industrial PLC I/O Module Bias | Medical Isolated Sensor Interface |
Use Scenario: Delivering isolated 15 V and 5 V rails for analog front-end op-amps, ADC references, and digital isolators in programmable logic controller I/O modules. IC Role / Device Role / Timing Role: Dual-output bias generator using transformer windings; LM34926SDX/NOPB controls primary winding while secondary taps provide multiple isolated outputs. Use Value: Integrated high- and low-side switches reduce footprint vs discrete solutions; 100 V rating accommodates 48 V DC fieldbus surges per IEC 61000-4-5 Level 3. | Use Scenario: Powering isolated signal-conditioning circuitry for patient-connected biosensors requiring reinforced galvanic isolation per IEC 60601-1. IC Role / Device Role / Timing Role: Secondary-side regulator in transformer-isolated DC-DC stage; COT control ensures stable operation despite variable sensor load currents and EMI-rich hospital environments. Use Value: Precision 1.225 V reference and 2% tolerance enable <±1% output accuracy - critical for calibrated medical measurements; no external compensation simplifies safety-certified layout. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar isolated bias regulator applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LM5165RGET | Wider 3–65 V input; integrated 150 mA LDO instead of synchronous buck; no BST/SW pins; fixed 1.22 V reference. | Suitable for non-isolated, low-power bias; lacks secondary-side fly-buck capability and high-side switch for transformer-coupled topologies. | Select LM5165RGET only for simpler, lower-current, non-isolated auxiliary rails where transformer coupling is unnecessary. |
| UCC28740DR | Primary-side QR flyback controller with opto-coupled feedback; no integrated power switches; requires external MOSFET and transformer. | Targets higher-power isolated supplies (>1 W); adds complexity but enables tighter cross-regulation across multiple outputs. | Choose UCC28740DR when multi-output isolation, tighter cross-regulation, or >500 mW output is required - not a drop-in replacement for LM34926SDX/NOPB's secondary-side integration. |
Compared with LM5165RGET and UCC28740DR, the LM34926SDX/NOPB uniquely combines high-voltage input tolerance (up to 100 V), integrated dual-MOSFET switching, and secondary-side COT control - making it the only option among the three that enables compact, low-component-count isolated bias generation without optocouplers or primary-side sensing.
Availability
LM34926SDX/NOPB is available at Aetrix Electronics and suitable for isolated telecom bias supply, automotive infotainment power, and industrial PLC I/O module applications requiring stable component supply, long-term lifecycle support, and guaranteed traceable sourcing.
Supply support for LM34926SDX/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 decades of expertise in high-reliability power conversion ICs.
The LM34926 product line targets cost-sensitive, space-constrained isolated DC-DC bias applications - specifically engineered to replace discrete MOSFET + controller solutions in fly-buck and transformer-coupled topologies across telecom, automotive, and industrial markets.
FAQ
What is the recommended minimum on-time for stable operation of the LM34926SDX/NOPB?
The LM34926SDX/NOPB requires a minimum on-time greater than 100 ns at maximum input voltage (100 V) for reliable COT control. This is enforced by selecting RON such that TON = K × RON / VIN remains above 100 ns - for example, RON = 250 kΩ yields ~370 ns at 75 V, satisfying the requirement. Operating below this threshold risks erratic switching or failure to regulate.
Can the LM34926SDX/NOPB operate without an external bootstrap capacitor?
No - the LM34926SDX/NOPB requires a 0.01 µF ceramic capacitor between BST and SW pins to sustain high-side gate drive. The internal diode charges this capacitor during each SW low phase; omitting it prevents proper high-side MOSFET turn-on and causes immediate functional failure. TI specifies X7R or better dielectric with low ESR for stability.
How does the LM34926SDX/NOPB achieve constant frequency across varying input voltage?
The LM34926SDX/NOPB achieves nearly constant frequency by implementing a constant-on-time (COT) control scheme where on-time is inversely proportional to VIN - TON = K × RON / VIN. As VIN increases, TON decreases, compensating for longer off-times and maintaining stable fSW. For example, with RON = 100 kΩ, fSW varies only ~15% across 7.5–100 V input, enabling predictable EMI filtering.
What is the purpose of the RC network in the LM34926SDX/NOPB feedback path?
The RC network (series resistor + capacitor from VOUT to FB) generates ≥25 mV resistive ripple at the FB pin - essential for stable COT operation. Since capacitive ripple is out-of-phase with inductor current, the RC network ensures monotonic FB voltage decay during off-time. Without sufficient ripple, the LM34926SDX/NOPB exhibits burst-mode instability or erratic switching, especially with low-ESR ceramic output capacitors.
Does the LM34926SDX/NOPB support remote shutdown functionality?
Yes - the LM34926SDX/NOPB supports remote shutdown via the UVLO pin. Pulling UVLO below 0.66 V (typical) forces the device into low-current shutdown mode (<225 µA), disabling switching and VCC regulation. This feature enables system-level power sequencing and fault recovery without removing input voltage - verified in Electrical Characteristics Table (Section 6.5) of the SNVS847F datasheet.
LM34926SDX/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)
LM34926SDX/NOPB FAQ
1.How can I place an order for LM34926SDX/NOPB through Aetrix?
Please submit a Request for Quotation (RFQ) for LM34926SDX/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 LM34926SDX/NOPB reliable?
The price and inventory of LM34926SDX/NOPB are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LM34926SDX/NOPB is usually 5 days.
3.What payment methods are accepted for LM34926SDX/NOPB?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LM34926SDX/NOPB transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LM34926SDX/NOPB?
LM34926SDX/NOPB orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LM34926SDX/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 LM34926SDX/NOPB?
For technical support, including LM34926SDX/NOPB datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LM34926SDX/NOPB requirements.
6.How does Aetrix verify that LM34926SDX/NOPB is sourced from the original manufacturer or authorized distributors?
All LM34926SDX/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 LM34926SDX/NOPB meets industry standards.
7.What is the process for return or replacement of LM34926SDX/NOPB?
All LM34926SDX/NOPB units undergo pre-shipment inspection (PSI). If there is an issue with LM34926SDX/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 LM34926SDX/NOPB part is unused and in its original packaging.
Return procedure for LM34926SDX/NOPB:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
LM34926SDX/NOPB Tags
-
TPS562201DDCR
Texas Instruments
-
MC34063ABD-TR
STMicroelectronics
-
TPS561201DDCR
Texas Instruments
-
MC33063ADR
Texas Instruments
-
MC34063ADR
Texas Instruments
-
TPS560200DBVR
Texas Instruments
-
AP3012KTR-G1
Diodes Incorporated
-
TLV61048DBVR
Texas Instruments
-
AZ34063UMTR-G1
Diodes Incorporated
-
TPS562200DDCR
Texas Instruments
-
AP62300TWU-7
Diodes Incorporated
-
MC34063EBD-TR
STMicroelectronics
Tech Hub
A practical engineering guide to 3.3V and 5V logic compatibility, input thresholds, resistor dividers, translator ICs, MOSFET level shifting, I2C pull-ups, timing limits and power-sequencing risks.
The 74HC595 uses push-pull logic outputs, while the TPIC6B595 uses 50 V open-drain DMOS sinks for higher-power loads. This guide compares timing, current limits, 3.3 V interfacing, load wiring, thermal…
The 74HC595 converts serial data into eight stable parallel outputs. This guide covers pin functions, shift and storage timing, OE and MR behavior, drive-current limits, cascading, voltage compatibilit…
A technical comparison of level-sensitive latches and edge-triggered flip-flops, covering timing windows, setup and hold limits, master–slave operation, time borrowing, race-through, HDL inference and…
A D latch stores one bit while Enable controls when data can pass. This reference covers gate-level operation, truth tables, transparency, setup and hold timing, LE versus OE, common ICs and practical …
An SR latch stores one bit through cross-coupled feedback. This engineering reference covers NOR and NAND implementations, truth tables, forbidden-state recovery, gated operation, switch debouncing, fa…
Latch circuits retain one bit through feedback. This technical reference covers SR and D latches, truth tables, transparency, timing limits, latch-versus-flip-flop behavior, applications and common log…
An engineering guide to LED driver operation, constant-current and constant-voltage outputs, linear and switching topologies, dimming, IC selection, calculations, replacement compatibility, and fault c…
Operational amplifier guide covering op amp basics, feedback, ideal vs real op amps, common configurations, buffer circuits, offset, bias current, gain-bandwidth, slew rate, rail-to-rail limits and sel…
Jumper cables guide covering safe connection order, red and black clamp placement, final ground connection, cable gauge, length, clamp quality, copper vs CCA cables, jump starter comparison and battery…
