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Texas Instruments LMR51420XFDDCR
- Part No.:
- LMR51420XFDDCR
- Manufacturer:
- Texas Instruments
- Package:
- SOT-23-6 Thin, TSOT-23-6
- Datasheet:
-
LMR51420XFDDCR.pdf
- Description:
- IC REG BUCK ADJ 2A SOT23
- Quantity:
- Payment:
- Shipping:
Inventory:4,333
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Product details
Overview
LMR51420XFDDCR from Texas Instruments is a synchronous buck DC-DC converter IC delivering up to 2-A continuous output current with 4.5-V to 36-V input range, fixed 500-kHz switching frequency, FPWM operation mode, and ±1.5% reference voltage accuracy in a 6-pin SOT-23 package - used for industrial power conditioning in motor drives and building automation systems.
For engineers reviewing the LMR51420XFDDCR datasheet, LMR51420XFDDCR pinout, LMR51420XFDDCR application, or LMR51420XFDDCR equivalent, key selection considerations include its FPWM mode for constant-frequency low-ripple regulation, 70-ns minimum on-time, internal compensation, precision enable with adjustable UVLO, and thermal/short-circuit protection with hiccup recovery.
Technical Context
The LMR51420XFDDCR employs fixed-frequency peak-current mode control with internal slope compensation and an integrated error amplifier. It uses synchronous rectification with separate high-side (0.12 Ω) and low-side (0.07 Ω) MOSFETs, enabling efficient CCM operation across wide VIN and load ranges.
Its FPWM mode maintains constant 500-kHz switching frequency from light to full load, ensuring tight output voltage regulation (±1.5% over temperature), low ripple, and predictable EMI behavior. Frequency foldback activates below 150-ns off-time or below 70-ns on-time to extend duty cycle range while preserving regulation down to 0.6-V output.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 4.5 V to 36 V - supports unregulated industrial rails including 12-V, 24-V, and 36-V battery or bus supplies. |
| Output Current | 2 A continuous - delivers full rated current without external current-sense resistors or heatsinking at TJ ≤ 125°C. |
| Switching Frequency | 500 kHz (fixed) - enables compact magnetics with typical 2.2–4.7 µH inductors and reduces EMI filter size. |
| Reference Voltage | 0.6 V ±1.5% - sets output via resistor divider; enables precise 3.3-V, 5-V, or custom outputs with minimal drift over –40°C to 150°C. |
| Min. On-Time | 70 ns - supports high step-down ratios (e.g., 36 V → 3.3 V) without requiring frequency foldback at light loads. |
| Thermal Shutdown | 163°C with 22°C hysteresis - protects against sustained overload or poor PCB thermal design; recovers automatically at 141°C. |
| Enable Threshold | 1.227 V (typ.) rising, 1.08 V (typ.) falling - allows accurate system-level UVLO using external resistor divider on EN pin. |
Pinout & Package
LMR51420XFDDCR is housed in a 6-pin SOT-23 (DBV) package measuring 2.90 mm × 1.60 mm, optimized for space-constrained industrial PCBs with thermal pad omitted - thermal performance relies on copper area under GND and VIN pins per JEDEC 4-layer board guidelines.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| GND | Power ground | Internal low-side FET source node; must connect directly to system ground plane and CIN/COUT ground pads with minimal trace length. |
| SW | Power switch node | Drain of low-side FET and source of high-side FET; connects to inductor; requires tight layout to minimize ringing and EMI. |
| VIN | Input supply | Bias and high-side gate drive source; bypassed with ≥10 µF ceramic capacitor placed adjacent to pin and GND. |
| FB | Feedback input | High-impedance analog input sensing output voltage via resistor divider; sensitive to noise - keep trace short and away from SW/VIN. |
| EN | Enable control | Logic-level precision enable; tied to VIN for self-start or configured with RENT/RENB for programmable UVLO; not floating. |
| CB | Bootstrap capacitor | Connects 100-nF X7R/X5R ceramic capacitor to SW; supplies gate drive for high-side FET during each switching cycle. |
Key Features
| Feature | Design Value |
|---|---|
| FPWM operation mode | Ensures constant 500-kHz frequency and low output voltage ripple across entire 0–2-A load range - critical for noise-sensitive analog or communication circuits. |
| Internal compensation | Eliminates need for external compensation network; supports stable operation with wide variety of output capacitors (including low-ESR ceramics) and simplifies BOM. |
| Start-up with prebiased output | Allows safe power-up into existing output voltage (e.g., hot-swap or backup rail scenarios) without reverse current or latch-up risk. |
| Hiccup-mode short-circuit protection | Disables switching for 135 ms after fault detection, then retries - prevents thermal runaway during sustained shorts while enabling automatic recovery. |
| 98% maximum duty cycle | Supports ultra-low dropout operation (e.g., 5.5-V input → 5-V output); extends usable input range in brownout conditions. |
Applications
| Motor Drives | Building Automation |
|---|---|
Use Scenario: Powering microcontrollers, gate drivers, and sensors in HVAC actuators and smart valve controllers operating from 24-V DC bus. IC Role / Device Role / Timing Role: Primary 3.3-V or 5-V point-of-load regulator converting noisy 24-V industrial rail to clean logic supply. Use Value: FPWM mode ensures stable MCU clocking and ADC reference despite variable motor load transients; 150°C junction rating supports enclosed enclosures. | Use Scenario: Supplying wireless sensor nodes (Zigbee, BLE) and occupancy detectors deployed in lighting control panels and fire alarm interfaces. IC Role / Device Role / Timing Role: Compact, rugged DC-DC converter powering mixed-signal SoCs and RF transceivers from 12-V or 24-V building power backbone. Use Value: 2.9 mm × 1.6 mm SOT-23 footprint saves board space in dense sensor modules; PFM/FPWM option allows efficiency vs. ripple trade-off per node requirement. |
| Appliances | General Purpose Wide VIN |
Use Scenario: Providing isolated 5-V and 3.3-V rails for control boards in washing machines, dishwashers, and refrigerators with variable AC-DC front-end outputs. IC Role / Device Role / Timing Role: Secondary regulator downstream of bulk 12–36-V intermediate bus, handling line and load transients from compressor or pump cycling. Use Value: 70-ns min on-time and frequency foldback maintain regulation during deep input dips; hiccup protection survives relay contact bounce or solenoid inrush. | Use Scenario: Flexible power solution for test equipment, portable diagnostics, and field-deployable instrumentation requiring operation from multiple input sources (battery, USB PD, wall adapter). IC Role / Device Role / Timing Role: Universal input buck converter supporting 4.5–36-V inputs and adjustable outputs via FB divider - used where single BOM serves multiple platforms. Use Value: Precision enable with external UVLO divider enables seamless switchover between power sources; ±1.5% VREF ensures accurate sensor biasing and DAC references. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar synchronous buck converter applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LMR51420XDDCR | Same 500-kHz frequency but PFM mode instead of FPWM - no constant-frequency operation at light load. | Higher light-load efficiency but larger output ripple and variable frequency; unsuitable for noise-sensitive or timing-critical loads. | Select when >90% efficiency at 1-mA load is prioritized over EMI control or ADC reference stability. |
| TPS54202DRCT | Pin-to-pin compatible; 4.5–28-V input, 2-A, 500-kHz, FPWM; lacks 36-V rating and 150°C junction rating. | Valid for 24-V systems only; not rated for 36-V automotive or industrial transients; lower thermal robustness limits high-ambient use. | Choose only if input never exceeds 28 V and ambient stays <105°C - verify thermal margin with actual layout. |
Compared with LMR51420XFDDCR, LMR51420XDDCR trades ripple and frequency stability for light-load efficiency, while TPS54202DRCT offers identical pinout but reduced input voltage and thermal capability - making LMR51420XFDDCR the sole choice for 36-V, high-temperature, constant-frequency designs.
Availability
LMR51420XFDDCR is available at Aetrix Electronics and suitable for motor drives, building automation, appliance control, and general-purpose wide-VIN power supplies requiring stable component supply, long-term lifecycle support, and consistent parametric performance across production batches.
Supply support for LMR51420XFDDCR 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 industrial and automotive power conversion.
The LMR51420 family was designed specifically for rugged industrial point-of-load applications demanding wide input range, small solution size, and functional safety readiness - targeting systems where reliability, thermal resilience, and ease of design are critical.
FAQ
What is the switching frequency of the LMR51420XFDDCR and is it adjustable?
The LMR51420XFDDCR operates at a fixed 500-kHz switching frequency and is not user-adjustable. This frequency is factory-trimmed and remains constant across load, line, and temperature in FPWM mode - enabling predictable EMI filtering and consistent inductor sizing. Unlike PFM variants, it does not enter burst mode or skip cycles at light load.
Does the LMR51420XFDDCR support start-up into a prebiased output voltage?
Yes, the LMR51420XFDDCR supports start-up with a prebiased output. Its control architecture prevents reverse current flow during power-up when VOUT is already present, making it suitable for hot-swap, redundant supply, or backup-battery applications. No external diode or circuitry is required to enable this feature in the LMR51420XFDDCR.
What is the maximum output voltage that can be set using the feedback divider on the LMR51420XFDDCR?
The LMR51420XFDDCR supports output voltages up to 95% of VIN, with practical upper limit constrained by minimum off-time and duty cycle. For example, at VIN = 36 V, maximum regulated VOUT is approximately 34.2 V. However, standard configurations target ≤12 V outputs; higher voltages require careful dead-time and loop-stability validation per the LMR51420XFDDCR datasheet Section 9.2.
How does the hiccup-mode short-circuit protection work in the LMR51420XFDDCR?
In hiccup mode, the LMR51420XFDDCR disables switching for 135 ms upon detecting a sustained short circuit, then attempts restart. If the fault persists, it repeats the cycle. This prevents thermal damage during indefinite overload while enabling automatic recovery once the fault clears - a key reliability feature confirmed in the LMR51420XFDDCR's electrical characteristics table and functional description.
Can the LMR51420XFDDCR be used with ceramic output capacitors only, or is an electrolytic capacitor required?
The LMR51420XFDDCR is fully compatible with ceramic-only output capacitors. Its internally compensated architecture and stable FPWM operation eliminate the need for bulk electrolytic capacitance. Designs commonly use 22–47 µF X5R/X7R ceramics with low ESR; total output capacitance ≥47 µF is recommended for transient response and ripple suppression per the LMR51420XFDDCR application guidelines.
LMR51420XFDDCR Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- SIMPLE SWITCHER®
- Package/Case:
- SOT-23-6 Thin, TSOT-23-6
- 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):
- 4.5V
- Voltage - Input (Max):
- 36V
- Voltage - Output (Min/Fixed):
- 0.6V
- Voltage - Output (Max):
- 34.2V
- Current - Output:
- 2A
- Frequency - Switching:
- 500kHz
- Synchronous Rectifier:
- Yes
- Operating Temperature:
- -40°C ~ 150°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- SOT-23-THIN
LMR51420XFDDCR FAQ
1.How can I place an order for LMR51420XFDDCR through Aetrix?
Please submit a Request for Quotation (RFQ) for LMR51420XFDDCR 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 LMR51420XFDDCR reliable?
The price and inventory of LMR51420XFDDCR are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LMR51420XFDDCR is usually 5 days.
3.What payment methods are accepted for LMR51420XFDDCR?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LMR51420XFDDCR transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LMR51420XFDDCR?
LMR51420XFDDCR orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LMR51420XFDDCR 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 LMR51420XFDDCR?
For technical support, including LMR51420XFDDCR datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LMR51420XFDDCR requirements.
6.How does Aetrix verify that LMR51420XFDDCR is sourced from the original manufacturer or authorized distributors?
All LMR51420XFDDCR 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 LMR51420XFDDCR meets industry standards.
7.What is the process for return or replacement of LMR51420XFDDCR?
All LMR51420XFDDCR units undergo pre-shipment inspection (PSI). If there is an issue with LMR51420XFDDCR, 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 LMR51420XFDDCR part is unused and in its original packaging.
Return procedure for LMR51420XFDDCR:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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