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Texas Instruments LM21305SQE/NOPB
- Part No.:
- LM21305SQE/NOPB
- Manufacturer:
- Texas Instruments
- Package:
- 28-WFQFN Exposed Pad
- Datasheet:
-
LM21305SQE/NOPB.pdf
- Description:
- IC REG BUCK ADJ 5A 28WQFN
- Quantity:
- Payment:
- Shipping:
Inventory:667
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Product details
Overview
LM21305SQE/NOPB from Texas Instruments is a monolithic synchronous buck DC-DC converter delivering up to 5 A output current with input voltage range 3 V to 18 V, adjustable switching frequency from 300 kHz to 1.5 MHz, 0.598-V reference accuracy, and integrated high-side (44 mΩ) and low-side (22 mΩ) MOSFETs. It serves as a core voltage regulator for FPGA, DSP, and telecom POL applications.
For engineers reviewing the LM21305SQE/NOPB datasheet, LM21305SQE/NOPB pinout, LM21305SQE/NOPB application, or LM21305SQE/NOPB equivalent, key selection criteria include minimum on-time (70 ns), diode emulation mode for light-load efficiency, PGOOD status signaling, thermal shutdown with 10°C hysteresis, and WQFN-28 package thermal performance (θJA = 36.9°C/W).
Technical Context
The LM21305SQE/NOPB implements peak current-mode control with adaptive slope compensation scaled to switching frequency, enabling stable operation across 0.598-V to 18-V output ranges and duty cycles up to 95%. Its internal error amplifier (65 dB gain, 2400 µS transconductance) drives COMP for loop compensation, while cycle-by-cycle overcurrent protection monitors both high-side (7 A typ) and low-side (8 A typ) MOSFETs.
It integrates dual LDO sub-regulators (2.5 V/2.47 V and 5.0 V/4.88 V), supports external frequency synchronization via FREQ pin with ±10%–+50% tolerance, and features monotonic soft-start (2.7 ms typ 10%–90% VFB) into pre-biased loads. UVLO thresholds on AVIN (2.93 V rising, 2.73 V falling) and OVP (109.5% VOUT) provide robust rail sequencing and fault containment.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 3 V to 18 V - supports direct interface to 3.3-V, 5-V, and 12-V intermediate bus rails |
| Output Current | 5 A continuous - enables single-chip core supply for mid-range FPGAs and DSPs |
| Switching Frequency | 300 kHz to 1.5 MHz - programmable via RFRQ resistor or external sync clock for EMI control |
| Feedback Reference | 0.598 V ±10 mV - enables precise low-VOUT regulation down to sub-1-V levels |
| Min On/Off Time | TON-MIN = 70 ns, TOFF-MIN = 50 ns - supports high duty-cycle operation at low VOUT |
| RDS(on) HS/LS | 44 mΩ / 22 mΩ at 5 A - reduces conduction loss and improves full-load efficiency |
| Quiescent Current | 4.1 µA in shutdown - minimizes standby power in always-on systems |
Pinout & Package
LM21305SQE/NOPB is housed in a thermally enhanced 5.0 mm × 5.0 mm WQFN-28 package with 0.5-mm pitch and exposed thermal pad (PAD) requiring connection to PGND via multiple vias for optimal thermal performance (θJB = 9.9°C/W).
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| PVIN (1,2,27,28) | Power Input | Primary high-current input rail connection for internal MOSFETs; must be decoupled with ≥10 µF ceramic |
| SW (3–6) | Switch Node | Drives external inductor; swings between PVIN and PGND; requires low-inductance layout to minimize ringing |
| PGND (7–10) | Power Ground | High-current return path for MOSFETs; separate from AGND to avoid noise coupling into analog circuitry |
| AGND (14,17–20,24) | Analog Ground | Reference for FB, COMP, FREQ, and internal bias circuits; must be star-connected to avoid ground bounce |
| FB (13) | Voltage Feedback | Senses regulated output via resistor divider; 0.598-V reference sets VOUT = 0.598 × (1 + R1/R2) |
| COMP (11) | Error Amplifier Output | Connects external RC network to set loop crossover frequency and phase margin for transient stability |
| FREQ (16) | Frequency Control | Accepts resistor-to-AGND (RFRQ) for oscillator setting or AC-coupled external clock (300 kHz–1.5 MHz) |
| EN (15) | Enable Input | Logic-level control with 1.2 V threshold and 200 mV hysteresis; allows programmable UVLO using external divider |
| PGOOD (12) | Power-Good Indicator | Open-drain output asserting high when VOUT is within ±4.2% of target; requires external pull-up to 5V0 or system rail |
| CBOOT (26) | Bootstrap Supply | Connects 100-nF capacitor to SW to generate gate drive voltage for high-side MOSFET |
| 2V5 (21), 5V0 (25) | Internal LDO Outputs | Provide 2.47 V and 4.88 V bias rails; bypassed with 100 nF and 1 µF ceramics respectively; loading not recommended |
| AVIN (22,23) | Analog Power Input | Supplies internal LDOs; can be tied to PVIN via RC filter or isolated rail to reduce noise injection |
Key Features
| Feature | Design Value |
|---|---|
| Diode Emulation Mode | Enables discontinuous conduction at light loads to eliminate reverse inductor current and boost efficiency below ~0.5 A |
| Adaptive Dead-Time Control | Prevents shoot-through by dynamically adjusting high/low-side gate timing based on MOSFET characteristics and load |
| Monotonic Soft-Start | Guarantees controlled ramp-up even into pre-biased outputs, avoiding negative current surges during power-up |
| Integrated Dual LDOs | Eliminates need for external 2.5-V and 5-V bias supplies, reducing BOM count and PCB area in multi-rail systems |
| Thermal Shutdown with Hysteresis | Shuts down at 160°C and restarts at 150°C, preventing thermal cycling damage during sustained overload conditions |
Applications
| Telecom Point-of-Load | FPGA Core Supply |
|---|---|
Use Scenario: Regulating 12-V backplane to 1.2-V core rail for 5G baseband processors in compact RRUs. IC Role / Device Role / Timing Role: Primary synchronous buck regulator providing tightly regulated, low-noise core voltage with fast load transient response. Use Value: 70-ns minimum on-time enables stable 1.2-V output at high duty cycle; PGOOD enables safe power sequencing with FPGA configuration logic. | Use Scenario: Delivering 5-A peak current to Xilinx Artix-7 FPGA core under dynamic logic switching. IC Role / Device Role / Timing Role: High-density DC-DC converter managing rapid current transients (0.1 A → 5 A in <10 µs) without output droop. Use Value: Peak current-mode control with high-bandwidth error amplifier achieves <±1% load regulation and <100-µs recovery from 90% load step. |
| Server Memory DIMM | Industrial Embedded Controller |
Use Scenario: Generating 1.8-V DDR3/DDR4 termination voltage from 5-V intermediate rail in space-constrained server modules. IC Role / Device Role / Timing Role: Compact, thermally optimized POL regulator supporting JEDEC-compliant voltage accuracy and ripple specs. Use Value: WQFN-28 package with exposed pad achieves θJB = 9.9°C/W, enabling 5-A operation without heatsink in 85°C ambient. | Use Scenario: Powering ARM Cortex-A53 SoC and peripheral I/O in fanless industrial gateway with wide input range (12 V ±20%). IC Role / Device Role / Timing Role: Robust, fault-protected buck converter handling line transients and thermal stress in uncontrolled environments. Use Value: Integrated OVP (109.5% trip), UVLO hysteresis (195 mV), and thermal shutdown with 10°C hysteresis ensure reliable operation across temperature and input variation. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar synchronous buck converter applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| TPS54560RGTT | Lower max current (5 A vs 6 A), fixed 500-kHz frequency, no FREQ sync capability, larger SOIC-8 package | Lacks diode emulation mode and programmable frequency; less suitable for EMI-sensitive or ultra-dense layouts | Choose for cost-sensitive, fixed-frequency designs where board space and light-load efficiency are secondary |
| MP2315GJ-Z | Higher RDS(on) (HS 65 mΩ, LS 35 mΩ), lower max frequency (1.2 MHz), no internal LDOs, smaller QFN-10 package | Requires external bias rails; lacks PGOOD and OVP; limited thermal performance (no exposed pad) | Choose for ultra-compact, low-cost applications with moderate current (<3.5 A) and relaxed protection requirements |
Compared with TPS54560RGTT and MP2315GJ-Z, LM21305SQE/NOPB delivers superior thermal management via its exposed-pad WQFN-28, full protection suite (OVP, UVLO, OTP), and design flexibility through frequency synchronization and dual-LDO integration-making it optimal for high-reliability, high-density POL systems.
Availability
LM21305SQE/NOPB is available at Aetrix Electronics and suitable for telecom infrastructure, FPGA power delivery, and industrial embedded computing requiring stable component supply, long-term lifecycle support, and traceable sourcing.
Supply support for LM21305SQE/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 ICs, with decades of expertise in high-efficiency DC-DC conversion.
The LM21305SQE/NOPB belongs to TI's high-density synchronous buck converter product line, engineered for space-constrained, high-performance point-of-load applications demanding wide VIN, precision VOUT, and comprehensive fault protection.
FAQ
What is the minimum output voltage supported by the LM21305SQE/NOPB?
The LM21305SQE/NOPB supports output voltages as low as 0.598 V, set by its internal precision feedback reference. This enables direct regulation of sub-1-V FPGA core rails and advanced processor cores. The 0.598-V reference has ±10 mV tolerance over temperature, ensuring tight regulation accuracy across –40°C to +125°C junction range. External resistor dividers scale this reference to higher output voltages while maintaining proportional accuracy.
How does the LM21305SQE/NOPB achieve high efficiency at light loads?
The LM21305SQE/NOPB achieves high light-load efficiency through diode emulation mode (DEM), which disables the low-side MOSFET when inductor current reaches zero, preventing reverse current flow and associated conduction losses. This mode activates automatically below ~0.5 A, transitioning the converter into discontinuous conduction mode (DCM). DEM is complemented by ultra-low shutdown quiescent current (4.1 µA) and optimized gate drivers that minimize switching losses at reduced frequencies.
Can the LM21305SQE/NOPB be synchronized to an external clock, and what are the requirements?
Yes, the LM21305SQE/NOPB supports external clock synchronization via the FREQ pin using a 100-pF AC-coupling capacitor (CFRQ). The external clock must operate between 300 kHz and 1.5 MHz, have peak-to-peak amplitude >1.5 V, duty cycle 20%–80%, and edge rate faster than 100 ns. The device retains a backup resistor (RFRQ) on FREQ to default to free-running mode if the external clock fails, ensuring uninterrupted operation without system reset.
What thermal management features does the LM21305SQE/NOPB include?
The LM21305SQE/NOPB incorporates thermal shutdown at 160°C with 10°C hysteresis for automatic recovery, plus a thermally enhanced WQFN-28 package featuring an exposed PAD connected to PGND. Thermal metrics include θJB = 9.9°C/W and θJA = 36.9°C/W (JEDEC standard board), enabling 5-A operation in 85°C ambient with proper PCB layout. Multiple vias under the PAD and copper pour on inner layers are required to realize specified thermal resistance.
Does the LM21305SQE/NOPB require external components for basic operation?
Yes, the LM21305SQE/NOPB requires external components for functional operation: an inductor (3.3 µH typical), input/output capacitors (10 µF CIN, 47 µF COUT ceramic), bootstrap capacitor (100 nF), frequency-setting resistor (RFRQ), and optional compensation network on COMP. While internal LDOs eliminate need for external bias rails, 2V5 and 5V0 pins must be bypassed with 100 nF and 1 µF ceramics respectively. No external MOSFETs or drivers are needed due to full monolithic integration.
LM21305SQE/NOPB Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- -
- Package/Case:
- 28-WFQFN Exposed Pad
- 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):
- 3V
- Voltage - Input (Max):
- 18V
- Voltage - Output (Min/Fixed):
- 0.598V
- Voltage - Output (Max):
- 18V
- Current - Output:
- 5A
- Frequency - Switching:
- 300kHz ~ 1.5MHz
- Synchronous Rectifier:
- Yes
- Operating Temperature:
- -40°C ~ 85°C (TA)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 28-WQFN (5x5)
LM21305SQE/NOPB FAQ
1.How can I place an order for LM21305SQE/NOPB through Aetrix?
Please submit a Request for Quotation (RFQ) for LM21305SQE/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 LM21305SQE/NOPB reliable?
The price and inventory of LM21305SQE/NOPB are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LM21305SQE/NOPB is usually 5 days.
3.What payment methods are accepted for LM21305SQE/NOPB?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LM21305SQE/NOPB transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LM21305SQE/NOPB?
LM21305SQE/NOPB orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LM21305SQE/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 LM21305SQE/NOPB?
For technical support, including LM21305SQE/NOPB datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LM21305SQE/NOPB requirements.
6.How does Aetrix verify that LM21305SQE/NOPB is sourced from the original manufacturer or authorized distributors?
All LM21305SQE/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 LM21305SQE/NOPB meets industry standards.
7.What is the process for return or replacement of LM21305SQE/NOPB?
All LM21305SQE/NOPB units undergo pre-shipment inspection (PSI). If there is an issue with LM21305SQE/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 LM21305SQE/NOPB part is unused and in its original packaging.
Return procedure for LM21305SQE/NOPB:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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