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Monolithic Power Systems Inc. NB638DL-LF-Z
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- Part No.:
- NB638DL-LF-Z
- Manufacturer:
- Monolithic Power Systems Inc.
- Package:
- 20-VFQFN Exposed Pad
- Datasheet:
-
NB638DL-LF-Z.pdf
- Description:
- IC REG BUCK ADJ 7A 20QFN
- Quantity:
- Payment:
- Shipping:
Inventory:1,880
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Product details
Overview
NB638DL-LF-Z 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 for fast transient response, integrates 30mΩ/12mΩ HS/LS MOSFETs, and features comprehensive protection including SCP, OCP, OVP, UVP, and thermal shutdown. Used in notebook I/O power and distributed POL systems.
For engineers reviewing the NB638DL-LF-Z datasheet, NB638DL-LF-Z pinout, NB638DL-LF-Z application, or NB638DL-LF-Z equivalent, key selection considerations include its QFN20 (3×4mm) package footprint, programmable soft-start time via external capacitor, PGOOD open-drain signaling with 1ms–2ms delay, and COT-based stability requirements for ceramic vs. POSCAP output capacitors.
Technical Context
The NB638DL-LF-Z implements a proprietary COT control architecture where ON-time is dynamically set by input voltage and an external resistor on the FREQ pin, enabling stable operation from 200kHz to 1MHz without external compensation. Its internal 30mΩ high-side and 12mΩ low-side MOSFETs eliminate external power switches while supporting up to 7A load current at ≤125°C junction temperature.
Protection logic includes cycle-by-cycle over-current detection with 40μs hold-off before latch-off, immediate short-circuit latch-off when FB drops below 50% of VREF (0.408V), and non-latching thermal shutdown at 150°C with 25°C hysteresis. The PGOOD pin asserts high after FB reaches 90% of VREF with delay proportional to soft-start time plus 0.5ms.
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 high-density POL applications. |
| Feedback Reference | 815mV ±8mV - enables precise 0.8V–14V output setting with <1% regulation error over line/load/temperature. |
| Switching Frequency | 200kHz to 1MHz - user-programmable via FREQ pin resistor; higher frequencies allow smaller LC filter components. |
| HS/LS RDS(on) | 30mΩ / 12mΩ - integrated MOSFETs reduce BOM count and PCB area; enable >90% peak efficiency at mid-load. |
| Soft-Start Current | 8.5μA - charges external SS capacitor linearly; sets ramp time independently of output capacitance value. |
| PGOOD Thresholds | Rising: 90% VFB; Falling: 85% VFB - provides reliable power sequencing signal with configurable delay (1–2ms). |
| Thermal Shutdown | 150°C with 25°C hysteresis - protects die during sustained overload or poor airflow; auto-recovery at ~125°C. |
Pinout & Package
Package: QFN20 (3mm × 4mm, 0.5mm pitch), exposed thermal pad, RoHS-compliant and halogen-free.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1, 11–16 | AGND / PGND | Analog and power ground pins - require separate low-impedance copper pours tied at single point near IC for noise immunity. |
| 2 | FREQ | Frequency programming input - connects to IN via resistor to set switching frequency; decoupled with 1nF capacitor. |
| 3 | FB | Feedback node - senses output via resistor divider; slope-sensitive to ESR/external ramp for COT loop stability. |
| 4 | SS | Soft-start control - internal 8.5μA current source charges/discharges external capacitor for controlled ramp-up/down. |
| 5 | EN | Enable input - active-high with 1.05–1.60V threshold and 250–550mV hysteresis; includes 1MΩ internal pull-down. |
| 6 | PGOOD | Open-drain power-good flag - pulled low until FB ≥ 90% VREF; delay = 0.5 × TSS + 0.5ms. |
| 7 | BST | Bootstrap supply - requires 0.1–1μF capacitor between BST and SW to bias high-side gate driver. |
| 8, 19 | IN | Main input supply - accepts 4.5–28V; requires local ceramic decoupling and low-impedance PCB routing. |
| 9, 10, 17, 18 | SW | Power switch node - high di/dt path; must use wide traces, multiple vias, and minimal loop area to reduce EMI. |
| 20 | VCC | Internal bias regulator output - supplies internal circuitry; requires 1μF ceramic decoupling placed adjacent to pin. |
Key Features
| Feature | Design Value |
|---|---|
| Constant-On-Time (COT) Control | Enables sub-10μs load transient response without external compensation; simplifies design for ceramic-output systems. |
| Integrated Power MOSFETs | 30mΩ HS + 12mΩ LS devices eliminate external switches, reduce layout complexity, and improve thermal performance. |
| Programmable Soft Start | External capacitor sets ramp time precisely - prevents inrush current and avoids current-limit triggering during startup. |
| Comprehensive Protection Suite | SCP latch-off, OCP with 40μs hold-off, OVP/UVP, UVLO (4.0V rising), and thermal shutdown ensure robust field operation. |
| Adjustable Output Range | 0.8V to 14V via FB resistor divider - supports DDR memory, ASIC cores, and multi-rail embedded subsystems. |
| QFN20 (3×4mm) Package | Space-constrained footprint with exposed thermal pad - enables high-power density in ultra-thin notebooks and optical modules. |
Applications
| Notebook I/O Power | Optical Communication Modules |
|---|---|
|
Use Scenario: Supplies 1.05V/5A to PCIe Gen4/Gen5 retimers and SerDes PHYs in thin-and-light laptops. IC Role / Device Role / Timing Role: Primary synchronous buck regulator providing tightly regulated, low-noise I/O voltage with fast transient recovery. Use Value: Maintains signal integrity under burst traffic loads; COT control ensures <5% output deviation during 3A/μs load steps. |
Use Scenario: Powers laser driver bias circuits and transimpedance amplifiers in 100G QSFP28 optical modules. IC Role / Device Role / Timing Role: High-efficiency POL converter delivering stable 3.3V/4A from 12V backplane with minimal thermal rise. Use Value: Integrated MOSFETs and QFN20 package enable compact layout within tight module height constraints (<2.5mm). |
| Distributed POL Systems | Networking Switch ASIC Rails |
|
Use Scenario: Provides localized 1.2V/7A supply for FPGA I/O banks in modular telecom baseband units. IC Role / Device Role / Timing Role: Point-of-load regulator with programmable frequency to avoid noise coupling into sensitive RF sections. Use Value: 200kHz–1MHz range allows optimal trade-off between efficiency and EMI filtering component size. |
Use Scenario: Generates 0.85V/6A core voltage for multi-core network processors in Layer 3 switches. IC Role / Device Role / Timing Role: High-current buck converter with PGOOD sequencing and thermal monitoring for system-level fault management. Use Value: PGOOD delay synchronized to soft-start ensures orderly power-up of downstream logic and memory interfaces. |
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, SOIC-8 package - lower current, wider VIN, no integrated LS-FET. | Suitable for low-power auxiliary rails only; lacks 7A capability and COT transient performance. | Select only if output current ≤0.6A and board space permits SOIC-8; not drop-in for NB638DL-LF-Z designs. |
| MPQ4572GQ-AEC1-Z | AEC-Q100 qualified, 4.5–36V, 7A, QFN20 (4×4mm), 1.2MHz fixed frequency - automotive-grade, larger footprint, no FREQ pin. | Designed for automotive infotainment and ADAS; includes enhanced ESD and AEC-Q100 stress testing. | Choose for automotive programs requiring qualification; not recommended for cost-sensitive consumer designs. |
Compared with MP2451DT-LF-Z, NB638DL-LF-Z delivers 11.7× higher output current and integrated dual MOSFETs; versus MPQ4572GQ-AEC1-Z, it offers programmable frequency and smaller 3×4mm footprint but lacks automotive qualification.
Availability
NB638DL-LF-Z is available at Aetrix Electronics and suitable for notebook I/O power, optical communication modules, and distributed POL systems requiring stable component supply with full traceability and lifecycle support.
Supply support for NB638DL-LF-Z 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 design centers in the US, China, and Taiwan.
The NB638 belongs to MPS's high-efficiency synchronous buck converter product line, engineered for compact, high-current POL applications in computing, networking, and optical infrastructure where thermal density and transient response are critical.
FAQ
What is the maximum allowable input voltage for NB638DL-LF-Z?
The absolute maximum input voltage is 30V, but the recommended operating range is 4.5V to 28V. Exceeding 28V risks violating the 30V absolute rating and may trigger overvoltage protection or cause permanent damage. Operation above 28V is not guaranteed and voids reliability specifications.
Can NB638DL-LF-Z operate with ceramic output capacitors?
Yes, but external ramp compensation (R4/C4) is required for stability in PWM mode due to low ESR. The datasheet specifies design equations for R4 and C4 values based on switching frequency, inductor value, and desired VFB slope. Without ramp, ceramic outputs cause subharmonic oscillation.
How does the soft-start time relate to the SS capacitor value?
Soft-start time (TSS) in milliseconds equals (CSS in nF) × (0.815V) ÷ 8.5μA. For example, a 10nF capacitor yields ~0.96ms ramp time. Minimum recommended CSS is 4.7nF when output capacitance exceeds 330μF to prevent current-limit triggering during startup.
What triggers the NB638DL-LF-Z short-circuit protection (SCP)?
SCP activates immediately when FB voltage falls below 50% of VREF (≤0.408V) *and* the current limit is detected - indicating a dead short. This causes immediate latch-off; recovery requires full power cycle, unlike OCP which allows automatic restart after 40μs hold-off.
Is NB638DL-LF-Z pin-compatible with other MPS buck converters?
No - NB638DL-LF-Z uses a unique QFN20 (3×4mm) pinout optimized for its COT control and integrated power stage. Pin functions like FREQ, SS, and BST differ from MP2315 or MP2451. Layout redesign and schematic updates are required for substitution.
What is the thermal resistance θJA for NB638DL-LF-Z in standard layout?
θJA is 48°C/W when mounted on a 4-layer JEDEC-standard PCB per JESD51-7. Achieving this requires proper thermal pad soldering, ≥4 thermal vias under the pad, and connection to inner ground plane. Poor layout can raise θJA above 65°C/W, limiting usable output current.
Why is NB638DL-LF-Z marked "NOT RECOMMENDED FOR NEW DESIGNS"?
MPS issued this notice in Rev. 1.19 (2017) due to newer-generation alternatives (e.g., MPQ4572, MP2459) offering improved efficiency, lower quiescent current, and enhanced protection. Existing designs may continue using NB638DL-LF-Z, but new projects should evaluate successors for long-term supply assurance.
NB638DL-LF-Z Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Monolithic Power Systems Inc.
- Series:
- -
- Package/Case:
- 20-VFQFN Exposed Pad
- Packaging:
- Cut Tape (CT)
- Product Status:
- Discontinued at Digi-Key
- 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-Z FAQ
1.How can I place an order for NB638DL-LF-Z through Aetrix?
Please submit a Request for Quotation (RFQ) for NB638DL-LF-Z 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-Z reliable?
The price and inventory of NB638DL-LF-Z 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-Z is usually 5 days.
3.What payment methods are accepted for NB638DL-LF-Z?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for NB638DL-LF-Z transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for NB638DL-LF-Z?
NB638DL-LF-Z orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your NB638DL-LF-Z 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-Z?
For technical support, including NB638DL-LF-Z datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your NB638DL-LF-Z requirements.
6.How does Aetrix verify that NB638DL-LF-Z is sourced from the original manufacturer or authorized distributors?
All NB638DL-LF-Z 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-Z meets industry standards.
7.What is the process for return or replacement of NB638DL-LF-Z?
All NB638DL-LF-Z units undergo pre-shipment inspection (PSI). If there is an issue with NB638DL-LF-Z, 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-Z part is unused and in its original packaging.
Return procedure for NB638DL-LF-Z:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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