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Monolithic Power Systems Inc. NB638DL-LF-P
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- Part No.:
- NB638DL-LF-P
- Manufacturer:
- Monolithic Power Systems Inc.
- Package:
- 20-VFQFN Exposed Pad
- Datasheet:
-
NB638DL-LF-P.pdf
- Description:
- IC REG BUCK ADJ 7A 20QFN
- Quantity:
- Payment:
- Shipping:
Inventory:2,271
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Product details
Overview
NB638DL-LF-P from Monolithic Power Systems is a fully integrated, high-frequency synchronous step-down DC/DC converter delivering 7A continuous output current across 4.5V–28V input and 0.8V–14V adjustable output. It employs Constant-On-Time (COT) control, integrates 30mΩ high-side and 12mΩ low-side MOSFETs, and features SCP/OCP/OVP/UVP/thermal shutdown in a QFN20 (3×4mm) package-used in notebook I/O power and distributed POL systems.
For engineers reviewing the NB638DL-LF-P datasheet, NB638DL-LF-P pinout, NB638DL-LF-P application, or NB638DL-LF-P equivalent, key selection criteria include COT-based transient response, programmable soft-start timing, PGOOD open-drain signaling, bootstrap gate drive architecture, and thermal shutdown hysteresis of 25°C.
Technical Context
The NB638DL-LF-P uses proprietary COT control with line feed-forward via the FREQ pin, enabling stable regulation without external compensation while achieving fast load-step response. Its internal 30mΩ/12mΩ MOSFET pair supports up to 12A peak current limit and operates in both CCM (heavy load) and skip-mode (light load) for efficiency optimization.
Feedback is sensed at the FB pin with 815mV ±8mV reference voltage; output voltage is set by an external resistor divider. The SS pin enables 8.5μA-controlled soft-start/stop ramping, and PGOOD provides open-drain status with 50% SS-time + 0.5ms delay relative to VFB reaching 90% of VREF.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 4.5V to 28V - supports wide industrial and computing rail inputs including 5V, 12V, and 24V systems. |
| Output Current | 7A continuous - sufficient for CPU core I/O, FPGA auxiliary rails, and ASIC power domains. |
| Switching Frequency | 200kHz to 1MHz - adjustable via FREQ pin resistor; enables compact LC filter design with ceramic output caps. |
| Feedback Reference | 815mV ±8mV - tight tolerance enables accurate output regulation down to 0.8V for low-voltage logic rails. |
| Protection Features | SCP, OCP, OVP (125% VREF), UVP (70% VREF), thermal shutdown (150°C, 25°C hysteresis) - full fault coverage without external circuitry. |
| Soft-Start Current | 8.5μA - linear ramp control allows precise startup timing; SS capacitor value directly sets ramp duration per equation (11). |
| Power Good Delay | 0.5ms + 50% of SS time - ensures reliable system sequencing and avoids false assertions during output settling. |
Pinout & Package
Package: QFN20 (3mm × 4mm, 0.5mm pitch), thermally enhanced with exposed PGND pad (pins 11–16). RoHS-compliant, lead-free, halogen-free.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 AGND | Analog Ground | Reference for feedback, soft-start, and enable comparators; must be isolated from noisy PGND paths. |
| 2 FREQ | Frequency Set Input | Resistor-to-IN connection sets ON-time and switching frequency; enables line feed-forward for improved transient immunity. |
| 3 FB | Feedback Input | Senses output voltage via resistor divider; 815mV reference enables 0.8V–14V output programming. |
| 4 SS | Soft-Start Control | 8.5μA internal current source charges/discharges external capacitor for controlled ramp-up/down of output voltage. |
| 5 EN | Enable Input | Active-high with 1.05–1.60V threshold and 250–550mV hysteresis; includes 1MΩ internal pull-down. |
| 6 PGOOD | Power-Good Output | Open-drain signal asserted high when VFB ≥ 90% VREF, delayed by 0.5ms + 50% SS time. |
| 7 BST | Bootstrap Supply | Connects 0.1–1μF capacitor between SW and BST to generate floating gate drive for high-side MOSFET. |
| 8,19 IN | Main Input Supply | Accepts 4.5–28V; requires local ceramic decoupling; wide traces and multiple vias recommended. |
| 9,10,17,18 SW | Switch Node | High dv/dt node connecting internal HS/LS MOSFETs; demands low-inductance layout and thermal relief. |
| 11–16 PGND | Power Ground | Primary return path for switch current and output; must connect directly to exposed thermal pad. |
| 20 VCC | Bias Supply | Internal 5V regulator output; requires 1μF ceramic decoupling close to pin for gate driver stability. |
Key Features
| Feature | Design Value |
|---|---|
| Integrated Power Stage | 30mΩ high-side + 12mΩ low-side MOSFETs eliminate external discrete switches and reduce BOM count. |
| Constant-On-Time Control | Enables <10μs load transient response without loop compensation components; simplifies design for dynamic loads. |
| Programmable Soft Start | Adjustable ramp time via external SS capacitor prevents inrush current and avoids current-limit triggering. |
| Proprietary Switching Loss Reduction | Optimized dead-time control and gate drive timing minimize shoot-through and conduction losses at high frequency. |
| Full Protection Suite | Non-latching UVLO, cycle-by-cycle OCP, latch-off SCP, OVP/UVP, and thermal shutdown ensure robust field operation. |
Applications
| Notebook I/O Power | Networking System POL |
|---|---|
|
Use Scenario: Providing regulated 1.05V/3A power to DDR memory interfaces and PCIe controller I/O banks in ultrabook platforms. IC Role / Device Role / Timing Role: Primary synchronous buck regulator with COT control ensuring sub-10μs response to burst memory access transients. Use Value: Eliminates need for external compensation and reduces solution size by 35% vs. traditional voltage-mode controllers. |
Use Scenario: Delivering 3.3V/5A to Ethernet PHYs and packet buffer ICs in enterprise switches with strict ripple requirements. IC Role / Device Role / Timing Role: Point-of-load regulator with PGOOD sequencing and soft-start coordination for multi-rail power-up. Use Value: 815mV reference tolerance and 7A capability meet IEEE 802.3bt compliance for PoE-powered network edge devices. |
| Optical Transceiver Modules | Distributed Power Architecture |
|
Use Scenario: Generating 1.8V/2.5A for laser driver bias and DSP cores in SFP+/QSFP+ optical modules operating at -40°C to +85°C. IC Role / Device Role / Timing Role: High-efficiency buck converter supporting skip-mode operation to maintain >85% efficiency at 10mA light load. Use Value: Thermal shutdown with 25°C hysteresis ensures reliability under sealed module thermal constraints. |
Use Scenario: Local 5V/7A conversion from 12V intermediate bus in server backplanes with dense component placement. IC Role / Device Role / Timing Role: Compact POL regulator using QFN20 (3×4mm) footprint to minimize PCB area in space-constrained slots. Use Value: Integrated 30mΩ/12mΩ MOSFETs achieve >92% peak efficiency at 12V→5V/5A, reducing thermal management complexity. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar synchronous step-down converter applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| MP2451DT-LF-Z | 4.5–36V input, 0.8–28V output, 0.6A max, fixed 2MHz frequency, no PGOOD or soft-start programmability. | Targeted at low-current sensor nodes and microcontroller rails-not suitable for 7A loads or sequencing-critical systems. | Select only for cost-sensitive, low-power applications where 7A capability and PGOOD are unnecessary. |
| MPQ4470AGL-Z | 4.5–36V input, 0.8–24V output, 7A continuous, integrated MOSFETs (25mΩ/15mΩ), but uses voltage-mode control with external compensation. | Requires full Type-II/III compensation network and lacks COT's inherent transient speed; larger solution size. | Prefer when design requires precise frequency synchronization or compatibility with legacy voltage-mode layouts. |
Compared with NB638DL-LF-P, MP2451DT-LF-Z lacks current capability and protection granularity, while MPQ4470AGL-Z trades COT's simplicity and speed for greater loop tuning flexibility-making NB638DL-LF-P optimal for compact, high-transient-response POL designs.
Availability
NB638DL-LF-P is available at Aetrix Electronics and suitable for notebook I/O power, networking POL systems, optical transceiver modules, and distributed power architectures requiring stable component supply and long-term lifecycle support.
Supply support for NB638DL-LF-P 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
Monolithic Power Systems (MPS) is a fabless semiconductor company specializing in high-performance analog and power ICs, with over two decades of leadership in DC/DC conversion technology.
The NB638 belongs to MPS's high-efficiency synchronous buck converter product line, designed specifically for space-constrained, fast-transient applications in computing, communications, and industrial equipment where minimal external components and robust protection are critical.
FAQ
What is the maximum allowable input voltage for NB638DL-LF-P?
The absolute maximum input voltage is 30V, but the recommended operating range is 4.5V to 28V. Exceeding 28V risks violating the 30V VIN rating and may trigger overvoltage stress on internal circuitry-even if thermal limits are not exceeded. Operation above 28V voids guaranteed performance and reliability specifications.
Does NB638DL-LF-P support forced PWM mode?
No-NB638DL-LF-P operates exclusively in automatic CCM/skip-mode based on load current. It does not include a MODE pin or external control to force continuous PWM operation. Light-load efficiency is maintained via skip-mode, and no external signal can override this behavior.
How is the switching frequency set, and what resistor value yields 500kHz?
Frequency is set via resistor R7 from FREQ to IN. Using Equation (3) from the datasheet, a 182kΩ resistor yields ~500kHz at VIN = 12V. The relationship is non-linear due to VIN feed-forward; actual frequency varies ±10% across input range and temperature.
Can NB638DL-LF-P drive ceramic output capacitors without external ramp compensation?
Yes-but only with careful attention to ESR and ramp design. For low-ESR ceramics, external ramp compensation (R4/C4) is required per Equation (5) and (9); omitting it causes subharmonic oscillation and instability in CCM. POSCAPs with sufficient ESR (>15mΩ) stabilize internally.
What is the thermal resistance θJA for the QFN20 (3×4mm) package?
The measured junction-to-ambient thermal resistance is 48°C/W on a standard 4-layer JEDEC PCB (JESD51-7). This value assumes proper thermal vias under the exposed PGND pad and 1-in² copper pour; inadequate layout can increase θJA by >20°C/W.
Is NB638DL-LF-P recommended for new designs?
No-the official datasheet states "NOT RECOMMENDED FOR NEW DESIGNS." While fully functional and supported, MPS advises migration to newer-generation alternatives such as the MPQ4470 or MPQ4572 for enhanced efficiency, lower quiescent current, and extended lifetime availability.
NB638DL-LF-P Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Monolithic Power Systems Inc.
- Series:
- -
- Package/Case:
- 20-VFQFN 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):
- 4.5V
- Voltage - Input (Max):
- 28V
- Voltage - Output (Min/Fixed):
- 0.8V
- Voltage - Output (Max):
- 13V
- Current - Output:
- 7A
- Frequency - Switching:
- 200kHz ~ 1MHz
- Synchronous Rectifier:
- Yes
- Operating Temperature:
- -40°C ~ 125°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 20-QFN (3x4)
NB638DL-LF-P FAQ
1.How can I place an order for NB638DL-LF-P through Aetrix?
Please submit a Request for Quotation (RFQ) for NB638DL-LF-P 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 NB638DL-LF-P reliable?
The price and inventory of NB638DL-LF-P are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for NB638DL-LF-P is usually 5 days.
3.What payment methods are accepted for NB638DL-LF-P?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for NB638DL-LF-P transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for NB638DL-LF-P?
NB638DL-LF-P orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your NB638DL-LF-P 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 NB638DL-LF-P?
For technical support, including NB638DL-LF-P datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your NB638DL-LF-P requirements.
6.How does Aetrix verify that NB638DL-LF-P is sourced from the original manufacturer or authorized distributors?
All NB638DL-LF-P 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 NB638DL-LF-P meets industry standards.
7.What is the process for return or replacement of NB638DL-LF-P?
All NB638DL-LF-P units undergo pre-shipment inspection (PSI). If there is an issue with NB638DL-LF-P, 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 NB638DL-LF-P part is unused and in its original packaging.
Return procedure for NB638DL-LF-P:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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