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Texas Instruments LM34923MM/NOPB
- Part No.:
- LM34923MM/NOPB
- Manufacturer:
- Texas Instruments
- Package:
- 10-TFSOP, 10-MSOP (0.118", 3.00mm Width)
- Datasheet:
-
LM34923MM/NOPB.pdf
- Description:
- IC REG BUCK ADJ 600MA 10VSSOP
- Quantity:
- Payment:
- Shipping:
Inventory:1,993
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Product details
Overview
LM34923MM/NOPB from Texas Instruments is a high-voltage, constant on-time synchronous-capable buck switching regulator with integrated 80-V N-channel MOSFET switch, 7.5-V internal VCC regulator, and programmable input UV detection. It operates from 6 V to 75 V input, delivers up to 600 mA output current, and regulates adjustable output voltages starting at 2.5 V - used in +42 V automotive systems and telecom secondary post-regulation.
For engineers reviewing the LM34923MM/NOPB datasheet, LM34923MM/NOPB pinout, LM34923MM/NOPB application, or LM34923MM/NOPB equivalent, key selection considerations include its no-loop-compensation architecture, VIN-inversely-proportional on-time control, intelligent foldback-free current limiting, bootstrap pre-charge for light-load stability, and 10-pin VSSOP package thermal performance (θJA = 200 °C/W).
Technical Context
The LM34923MM/NOPB implements a constant-frequency, constant-on-time control scheme where on-time (TON) scales inversely with VIN via external RT resistor, enabling stable operation across 6–75 V input without loop compensation. Its regulation relies on comparing FB voltage to a precision 2.5 V reference, with overvoltage protection triggered at 2.85 V.
Current limiting uses a forced off-time generator whose duration is inversely proportional to VOUT, ensuring short-circuit safety while minimizing foldback during moderate overloads. The integrated 80-V N-channel buck switch, bootstrap gate drive (BST–SW), and pre-charge switch enable reliable high-side switching with no external driver required.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 6 V to 75 V - supports wide-range industrial, telecom, and 42 V automotive bus inputs with 80 V transient tolerance. |
| Output Current | 600 mA - continuous load capability with current limit threshold of 700–1500 mA, validated across −40°C to +125°C. |
| Switching Control | Constant on-time, VIN-inversely proportional - maintains stable frequency under line/load variation; no external compensation needed. |
| Feedback Reference | 2.5 V ±2.5% - enables precise output setting via RFB1/RFB2 divider; overvoltage cutoff at 2.85 V protects downstream circuitry. |
| Integrated VCC Regulator | 7.5 V regulated output, 30 mA current limit - powers internal gate driver and logic; eliminates need for external bias supply. |
| UV Detection | Programmable via resistor divider on UV pin; 2.5 V threshold with 5 µA hysteresis current - provides configurable brown-out monitoring with open-drain UVO status flag. |
| Thermal Protection | 165°C shutdown with 20°C hysteresis - prevents catastrophic failure during overload or poor heatsinking; resumes at 145°C. |
Pinout & Package
LM34923MM/NOPB is housed in a thermally enhanced 10-pin VSSOP (Very Small Outline Package) with 0.5 mm pitch, optimized for high-voltage DC/DC conversion in space-constrained applications. Package dimensions: 3.0 mm × 3.0 mm × 1.0 mm (max height), exposed pad not present.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 SW | Switching Node | Power switching node connecting to inductor, freewheeling diode/synchronous FET, and BST capacitor; handles full switching current and voltage transitions. |
| 2 BST | Bootstrap Supply | Charged from VCC through internal diode when SW is low; requires ≥0.01 µF ceramic capacitor to SW for high-side gate drive. |
| 3 N/C | No Connect | Internally unused; must remain unconnected and floating per datasheet. |
| 4 RTN | Signal Ground | Reference ground for all analog and power circuits; separate from high-current return paths to minimize noise coupling. |
| 5 UV | UV Threshold Input | Accepts resistor-divider voltage for programmable input undervoltage detection; internal 5 µA sink enables hysteresis. |
| 6 UVO | UV Status Output | Open-drain flag active-low when UV < 2.5 V, VCC UVLO active, or RT/SD asserted - enables system-level fault reporting. |
| 7 FB | Feedback Input | Inverting input of regulation comparator; connected to resistor divider from VOUT; 1 nA bias current minimizes divider error. |
| 8 RT/SD | On-Time Set / Shutdown | Resistor sets on-time inversely vs VIN; pulled to GND disables regulator - dual-function pin simplifies design and reduces BOM count. |
| 9 VCC | Internal Bias Supply | 7.5 V regulated output powering gate driver and control logic; requires 1 µF ceramic capacitor to RTN for stability. |
| 10 VIN | Main Power Input | Primary input connection for 6–75 V supply; withstands 80 V transients; feeds internal VCC regulator and buck switch. |
Key Features
| Feature | Design Value |
|---|---|
| No loop compensation required | Constant on-time architecture eliminates external compensation network - reduces component count, layout sensitivity, and startup tuning effort. |
| Ultra-fast transient response | On-time control with no integrator delay enables immediate reaction to load steps - critical for burst-mode or dynamic load applications. |
| Intelligent current limit | Off-time scales inversely with VOUT - ensures robust short-circuit protection while minimizing foldback during partial overloads. |
| Pre-charge switch for bootstrap | 150 ns pulse during minimum off-time recharges BST capacitor - prevents gate drive dropout during light-load or pre-biased start-up conditions. |
| Programmable input UV detector | Resistor-programmable threshold with open-drain UVO flag - enables flexible brown-out management without external supervisor IC. |
Applications
| Non-Isolated Telecom Buck Regulator | +42 V Automotive Systems |
|---|---|
Use Scenario: Regulating 48 V telecom bus down to 3.3 V or 5 V for baseband processors and interface ICs in central office equipment. IC Role / Device Role / Timing Role: Primary non-isolated step-down converter providing stable, efficient bias power with minimal external components. Use Value: Eliminates need for isolated flyback or external LDO stages - reduces cost, board area, and thermal stress in high-density telecom modules. | Use Scenario: Converting 42 V battery rail to 5 V for infotainment head units, ADAS camera modules, or body control ECUs in next-gen vehicles. IC Role / Device Role / Timing Role: High-input-voltage buck regulator with robust UVLO and thermal shutdown for automotive-grade reliability. Use Value: Withstands load dump transients up to 80 V and operates continuously from −40°C to +125°C junction temperature. |
| Secondary High Voltage Post Regulator | Industrial 24–75 V DC Power Distribution |
Use Scenario: Tight-regulation post-converter after a front-end AC/DC or isolated DC/DC stage supplying 24–60 V intermediate bus. IC Role / Device Role / Timing Role: Precision-adjustable buck regulator delivering low-noise, low-ripple outputs for sensitive analog or RF subsystems. Use Value: 2.5 V ±2.5% reference and 2.85 V OV protection ensure consistent output accuracy and prevent downstream damage during fault events. | Use Scenario: Powering PLC I/O modules, motor drives, or fieldbus nodes from unregulated 24–75 V industrial DC rails. IC Role / Device Role / Timing Role: Robust, self-contained buck controller supporting wide input range and programmable brown-out detection. Use Value: Integrated VCC regulator and pre-charge switch maintain gate drive integrity even under intermittent or low-duty-cycle loads. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar buck regulator applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LM5164QDDARQ1 | Automotive-grade (AEC-Q100), 100 V max input, 300 mA output, current-mode control with external compensation. | Requires loop compensation; higher VIN rating but lower output current; designed for automotive safety-critical systems. | Choose for AEC-Q100 compliance and 100 V transient immunity; avoid if no-compensation simplicity is required. |
| TPS54260DGQR | 60 V max input, 2.5 A output, current-mode control, integrated high-side FET, requires external compensation. | Higher current capability and lower RDS(on), but lacks programmable UV detection and pre-charge switch. | Choose for >600 mA loads or tighter thermal constraints; avoid if UV flag or light-load bootstrap stability is essential. |
Compared with LM34923MM/NOPB, LM5164QDDARQ1 adds automotive qualification and higher voltage margin but sacrifices no-compensation simplicity and integrated UV flag functionality; TPS54260DGQR offers higher output current and better efficiency at heavy loads but increases design complexity with mandatory compensation and lacks the intelligent current-limit off-time behavior.
Availability
LM34923MM/NOPB is available at Aetrix Electronics and suitable for non-isolated telecom buck regulators, +42 V automotive systems, and secondary high-voltage post regulators requiring stable component supply, long-term lifecycle support, and traceable sourcing.
Supply support for LM34923MM/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 delivering analog, embedded processing, and connectivity solutions for industrial, automotive, and communications markets.
The LM34923MM/NOPB belongs to TI's high-voltage DC/DC converter product line, engineered specifically for cost-sensitive, high-reliability buck applications operating directly from 6–75 V input rails without external bias supplies.
FAQ
What is the minimum on-time specification for LM34923MM/NOPB and why does it matter?
The LM34923MM/NOPB specifies a minimum on-time of 200 ns at maximum input voltage (75 V). This parameter directly limits the maximum achievable switching frequency - for example, at 75 V input and 5 V output, the theoretical max frequency is ~667 kHz. Violating this minimum can cause loss of current limit functionality and unstable regulation. Designers must select the RT resistor to ensure on-time stays above this threshold across the full VIN range, as confirmed in the LM34923MM/NOPB datasheet Section 8.2.1.
Does LM34923MM/NOPB require an external bootstrap capacitor, and what are its requirements?
Yes, LM34923MM/NOPB requires an external ceramic capacitor between BST and SW pins. The datasheet specifies a minimum value of 0.01 µF, with X7R or C0G dielectric recommended for stability. This capacitor supplies gate drive voltage for the internal N-channel high-side switch during on-time. Placement must be adjacent to the BST and SW pins to minimize parasitic inductance - poor placement can cause gate drive droop and erratic switching in the LM34923MM/NOPB.
How does the programmable UV detection work on LM34923MM/NOPB, and what is the role of the UVO pin?
The LM34923MM/NOPB uses an external resistor divider from VIN to set the UV threshold on the UV pin, with a fixed 2.5 V internal comparator reference. When UV falls below 2.5 V, the open-drain UVO pin pulls low, signaling undervoltage condition. UVO also asserts low during VCC UVLO or RT/SD shutdown - making it a unified fault flag. The internal 5 µA hysteresis current ensures clean release when input recovers, and the LM34923MM/NOPB datasheet provides exact resistor calculation formulas in Section 9.2.3.
Can LM34923MM/NOPB operate in discontinuous conduction mode (DCM), and how does it affect efficiency?
Yes, LM34923MM/NOPB automatically transitions into DCM at light loads, reducing switching frequency to maintain high efficiency - typical efficiency remains >80% even at 10 mA output. In DCM, inductor current fully discharges each cycle, eliminating reverse recovery losses in the freewheeling diode. This behavior is inherent to the constant on-time architecture and requires no mode-select configuration; the LM34923MM/NOPB datasheet confirms DCM operation down to zero load in Figure 2 and Section 8.3.4.
What is the purpose of the pre-charge switch in LM34923MM/NOPB, and when is it active?
The pre-charge switch in LM34923MM/NOPB applies a 150 ns pulse across BST–SW during the minimum off-time period to replenish charge lost from the bootstrap capacitor - critical during very light loads or long off-times where leakage could drop BST voltage below the gate drive UVLO threshold (2.15–3.8 V). It also activates during current-limit forced off-time and startup, preventing bootstrap collapse when output is pre-biased. This feature is unique to the LM34923MM/NOPB among TI's high-voltage buck regulators and is documented in Section 8.3.7.
LM34923MM/NOPB Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- -
- Package/Case:
- 10-TFSOP, 10-MSOP (0.118", 3.00mm Width)
- Packaging:
- Tape & Reel (TR)
- Product Status:
- Active
- Function:
- Step-Down
- Output Configuration:
- Positive
- Topology:
- Buck
- Output Type:
- Adjustable
- Number of Outputs:
- 1
- Voltage - Input (Min):
- 6V
- Voltage - Input (Max):
- 75V
- Voltage - Output (Min/Fixed):
- 2.5V
- Voltage - Output (Max):
- 75V
- Current - Output:
- 600mA
- Frequency - Switching:
- -
- Synchronous Rectifier:
- No
- Operating Temperature:
- -40°C ~ 125°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 10-VSSOP
LM34923MM/NOPB FAQ
1.How can I place an order for LM34923MM/NOPB through Aetrix?
Please submit a Request for Quotation (RFQ) for LM34923MM/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 LM34923MM/NOPB reliable?
The price and inventory of LM34923MM/NOPB are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LM34923MM/NOPB is usually 5 days.
3.What payment methods are accepted for LM34923MM/NOPB?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LM34923MM/NOPB transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LM34923MM/NOPB?
LM34923MM/NOPB orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LM34923MM/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 LM34923MM/NOPB?
For technical support, including LM34923MM/NOPB datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LM34923MM/NOPB requirements.
6.How does Aetrix verify that LM34923MM/NOPB is sourced from the original manufacturer or authorized distributors?
All LM34923MM/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 LM34923MM/NOPB meets industry standards.
7.What is the process for return or replacement of LM34923MM/NOPB?
All LM34923MM/NOPB units undergo pre-shipment inspection (PSI). If there is an issue with LM34923MM/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 LM34923MM/NOPB part is unused and in its original packaging.
Return procedure for LM34923MM/NOPB:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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