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Texas Instruments LM34927SDX/NOPB
- Part No.:
- LM34927SDX/NOPB
- Manufacturer:
- Texas Instruments
- Package:
- 8-WDFN Exposed Pad
- Datasheet:
-
LM34927SDX/NOPB.pdf
- Description:
- IC REG BUCK ADJ 600MA 8WSON
- Quantity:
- Payment:
- Shipping:
Inventory:4,825
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Product details
Overview
LM34927SDX/NOPB from Texas Instruments is a high-voltage integrated secondary-side bias regulator for isolated DC-DC converters, featuring dual 100-V N-channel MOSFETs (high-side buck + low-side synchronous switch), constant on-time (COT) control, and operation across 7.5 V to 100 V input. It delivers adjustable output voltage starting at 1.225 V with ±2% reference accuracy and supports up to 1 MHz switching frequency in telecom and industrial isolated power supplies.
For engineers reviewing the LM34927SDX/NOPB datasheet, LM34927SDX/NOPB pinout, LM34927SDX/NOPB application, or LM34927SDX/NOPB equivalent, key selection considerations include its 100-V input rating, integrated dual-switch architecture, COT control eliminating loop compensation, programmable UVLO and on-time, and thermal shutdown with 165°C trip point.
Technical Context
The LM34927SDX/NOPB implements a constant on-time (COT) control scheme where on-time is inversely proportional to VIN and set by an external RON resistor - enabling near-constant frequency across wide input ranges. 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 two 100-V N-channel MOSFETs: a high-side buck switch (RDS(ON) = 0.8–1.8 Ω) and a low-side synchronous rectifier (RDS(ON) = 0.45–1 Ω), both driven by an internal bootstrap circuit requiring a 0.01-μF BST–SW capacitor. An intelligent peak current limit (1.02 A typ.) initiates a variable off-time inversely proportional to VFB and VIN for short-circuit and overload protection.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 7.5 V to 100 V - enables direct connection to 48 V telecom buses and automotive 24/48 V systems without pre-regulation. |
| Output Voltage Accuracy | ±2% at FB pin (1.225 V reference) - ensures tight regulation of isolated bias rails under line/load/temperature variation. |
| Switching Frequency | Adjustable up to 1 MHz via RON - allows optimization of size vs. efficiency in space-constrained isolated designs. |
| Buck Switch RDS(ON) | 0.8–1.8 Ω (at ITEST = 200 mA, BST–SW = 7 V) - defines conduction loss and thermal performance at full load. |
| Synchronous Rectifier RDS(ON) | 0.45–1 Ω (at ITEST = 200 mA) - eliminates external Schottky diode, improving efficiency and reducing BOM count. |
| Current Limit Threshold | 0.7–1.3 A (peak) - provides robust short-circuit protection while maintaining fast transient recovery via adaptive off-time. |
| Thermal Shutdown | 165°C trip, 20°C hysteresis - prevents catastrophic failure during sustained overload or poor PCB thermal design. |
Pinout & Package
LM34927SDX/NOPB is packaged in an 8-pin WSON (4.00 mm × 4.00 mm) with exposed thermal pad, optimized for high-voltage isolation and thermal dissipation in compact bias supplies.
| 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 and electrical integrity. |
| 2 VIN | Main HV input | Accepts 7.5–100 V DC; powers internal VCC regulator and high-side switch; requires local ceramic input capacitance. |
| 3 UVLO | Undervoltage enable | Resistor-divider programmable startup threshold (1.225 V rising); pulled below 0.66 V forces shutdown mode. |
| 4 RON | On-time programming | Resistor-to-VIN sets minimum on-time (≥100 ns at max VIN); determines operating frequency and stability margin. |
| 5 FB | Voltage feedback | Compares output divider voltage to 1.225 V reference; requires ≥25 mV ripple for stable COT operation. |
| 6 VCC | Internal bias supply | 7.6 V regulated output (6.25–8.55 V); powers gate drivers and logic; requires 1.0 μF decoupling capacitor. |
| 7 BST | Bootstrap supply | Charged from VCC via internal diode when SW is low; supplies floating gate drive for high-side N-MOSFET. |
| 8 SW | Power switching node | Drives external inductor; connects to BST capacitor; voltage swings from RTN to VIN during operation. |
Key Features
| Feature | Design Value |
|---|---|
| No loop compensation required | Constant on-time (COT) architecture eliminates external compensation network - reduces design time and component count. |
| No Schottky diode needed | Integrated low-side synchronous MOSFET replaces lossy external diode - improves efficiency by ~3–5% at light-to-moderate loads. |
| Ultra-fast transient response | COT control enables immediate on-time retriggering upon FB dip - achieves <10 µs recovery from 50% load step in typical designs. |
| Intelligent peak current limit | Off-time scales inversely with FB voltage and VIN - minimizes foldback during overload while ensuring safe short-circuit handling up to 100 V. |
| Programmable UVLO and shutdown | External resistor divider on UVLO pin sets custom start-up voltage and enables remote shutdown - supports system-level sequencing and fault management. |
Applications
| Isolated Telecom Bias Supply | Automotive Isolated Auxiliary Rail |
|---|---|
|
Use Scenario: Generating a stable 5 V or 3.3 V bias rail from a 48 V intermediate bus in telecom base station power modules. IC Role / Device Role / Timing Role: Secondary-side synchronous buck controller regulating isolated auxiliary voltage using transformer-coupled winding feedback. Use Value: Eliminates optocoupler and TL431, reduces component count by ≥4 parts, and maintains ±2% output accuracy across –40°C to +125°C. |
Use Scenario: Providing isolated 12 V bias for CAN transceivers and microcontrollers in EV battery management systems (BMS). IC Role / Device Role / Timing Role: High-reliability secondary-side regulator deriving power from main DC-DC converter's auxiliary winding. Use Value: Withstands 100 V transients per ISO 7637-2; thermal shutdown protects against enclosure overheating; 7.5 V min start-up supports cold-cranking conditions. |
| Industrial PLC Isolated I/O Power | Medical Equipment Auxiliary Supply |
|
Use Scenario: Delivering isolated 15 V/200 mA bias for analog front-end op-amps and ADCs in programmable logic controllers. IC Role / Device Role / Timing Role: Compact, self-contained bias regulator replacing discrete MOSFET + controller solutions in space-limited DIN-rail modules. Use Value: WSON-8 package with exposed pad achieves 41.3°C/W θJA - enables convection-cooled operation without heatsink at ≤1 W output. |
Use Scenario: Generating isolated 3.3 V for digital logic in patient-connected diagnostic devices requiring reinforced insulation. IC Role / Device Role / Timing Role: Safety-certified secondary-side controller supporting creepage/clearance compliance via transformer isolation. Use Value: No external Schottky or compensation components simplifies safety certification; 1.225 V reference tolerance meets IEC 60601-1 ripple and accuracy requirements. |
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 | Wider 3–65 V input range; integrated 150-mA LDO instead of dual switches; requires external high-side FET for >100 V operation. | Designed for automotive AEC-Q100 Grade 1; lacks 100-V capability and synchronous rectification - unsuitable for telecom 48 V+ or industrial 100 V inputs. | Select LM5165QDGSRQ1 only if input stays ≤65 V and system requires AEC-Q100 qualification; not a drop-in replacement for LM34927SDX/NOPB. |
| UCC28740DR | Primary-side quasi-resonant flyback controller; no secondary-side integration; requires optocoupler and TL431 for regulation. | Targets cost-sensitive AC-DC adapters; lacks integrated secondary switches and COT control - higher BOM count and slower transient response. | Choose UCC28740DR for primary-side-controlled flyback topologies; LM34927SDX/NOPB is preferred when secondary-side regulation, simplicity, and speed are critical. |
Compared with LM5165QDGSRQ1 and UCC28740DR, the LM34927SDX/NOPB uniquely combines 100-V input tolerance, integrated dual N-MOSFETs, and COT control - delivering lower component count, faster transient response, and simpler layout for isolated bias supplies above 48 V.
Availability
LM34927SDX/NOPB is available at Aetrix Electronics and suitable for isolated telecom bias supplies, automotive auxiliary rails, and industrial PLC I/O power requiring stable component supply, long-term lifecycle support, and guaranteed traceable sourcing.
Supply support for LM34927SDX/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 designing analog ICs, embedded processors, and power management solutions for industrial, automotive, and communications markets.
The LM34927SDX/NOPB belongs to TI's high-voltage DC-DC controller product line, engineered specifically for simplified, efficient secondary-side bias regulation in isolated power architectures - targeting reduced design cycle time and improved reliability in harsh-input environments.
FAQ
What is the minimum input voltage required for LM34927SDX/NOPB to start regulation?
The LM34927SDX/NOPB requires a minimum input voltage of 7.5 V to initiate regulation. This is enabled once the internal VCC regulator reaches its 4.5 V UVLO threshold and the UVLO pin voltage exceeds 1.225 V. Below 7.5 V, the device remains in shutdown or standby mode, drawing only 50–225 µA quiescent current.
Does LM34927SDX/NOPB require an external Schottky diode?
No, the LM34927SDX/NOPB does not require an external Schottky diode. It integrates a low-side synchronous N-channel MOSFET rectifier (RDS(ON) = 0.45–1 Ω) that replaces the diode entirely, improving efficiency and eliminating reverse recovery losses. This is explicitly stated in the Features section of the datasheet.
How is the switching frequency set on LM34927SDX/NOPB?
The switching frequency of LM34927SDX/NOPB is determined by the external RON resistor and input voltage (VIN), per the equation TON = K × RON / VIN (K = 9×10⁻¹¹). Since on-time is inversely proportional to VIN, frequency remains nearly constant across the 7.5–100 V input range - enabling predictable EMI behavior and filter design.
What thermal protection features does LM34927SDX/NOPB include?
The LM34927SDX/NOPB includes thermal shutdown with a 165°C trip point and 20°C hysteresis. When junction temperature exceeds 165°C, the controller disables the buck switch and VCC regulator, entering a low-power reset state. Operation resumes automatically when temperature falls below 145°C, preventing permanent damage during overload or poor thermal design.
Can LM34927SDX/NOPB operate without output voltage ripple at the FB pin?
No, LM34927SDX/NOPB requires ≥25 mV of monotonic ripple at the FB pin for stable constant-on-time (COT) operation. This ripple must be resistive (ESR-based) or generated via external RC/Cr networks - capacitive-only ripple causes instability. The datasheet specifies three validated ripple generation methods to ensure reliable regulation.
LM34927SDX/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:
- 600mA
- 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)
LM34927SDX/NOPB FAQ
1.How can I place an order for LM34927SDX/NOPB through Aetrix?
Please submit a Request for Quotation (RFQ) for LM34927SDX/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 LM34927SDX/NOPB reliable?
The price and inventory of LM34927SDX/NOPB are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LM34927SDX/NOPB is usually 5 days.
3.What payment methods are accepted for LM34927SDX/NOPB?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LM34927SDX/NOPB transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LM34927SDX/NOPB?
LM34927SDX/NOPB orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LM34927SDX/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 LM34927SDX/NOPB?
For technical support, including LM34927SDX/NOPB datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LM34927SDX/NOPB requirements.
6.How does Aetrix verify that LM34927SDX/NOPB is sourced from the original manufacturer or authorized distributors?
All LM34927SDX/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 LM34927SDX/NOPB meets industry standards.
7.What is the process for return or replacement of LM34927SDX/NOPB?
All LM34927SDX/NOPB units undergo pre-shipment inspection (PSI). If there is an issue with LM34927SDX/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 LM34927SDX/NOPB part is unused and in its original packaging.
Return procedure for LM34927SDX/NOPB:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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