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onsemi FAN2108EMPX
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- Part No.:
- FAN2108EMPX
- Manufacturer:
- onsemi
- Package:
- 25-WQFN Exposed Pad
- Datasheet:
-
FAN2108EMPX.pdf
- Description:
- IC REG BUCK ADJ 8A 25MLP
- Quantity:
- Payment:
- Shipping:
Inventory:2,355
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Product details
Overview
FAN2108EMPX from ON Semiconductor is a fully integrated synchronous buck regulator delivering up to 8 A output current with 3–24 V input range, 0.8 V to 80% VIN adjustable output, and peak efficiency exceeding 95%. It integrates high- and low-side MOSFETs, controller, driver, internal bootstrap diode, and power-good signaling in a single 5 × 6 mm MLP package - designed for point-of-load regulation in graphics cards and high-end computing systems.
For engineers reviewing the FAN2108EMPX datasheet, pinout, applications, or equivalent options, key selection criteria include its -40°C to +85°C operating temperature range, programmable 200–600 kHz switching frequency via external RT resistor, lossless current-mode control architecture, pre-bias startup capability, and comprehensive protection suite including over-current, over-voltage, under-voltage, and thermal shutdown.
Technical Context
The FAN2108EMPX implements a summing current-mode modulator with voltage feedforward for stable operation across wide input voltage ranges. Its lossless current sensing enables accurate over-current protection and precise current limit programming via the ILIM pin using an external resistor.
It features an internal soft-start ramp (T0.8 = 5.3 ms, T1.0 = 6.7 ms), programmable frequency (200–600 kHz), and external compensation support for flexible loop tuning. The integrated Schottky diode on the low-side MOSFET and internal bootstrap diode reduce conduction losses and simplify layout.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 3 V to 24 V - supports wide-range industrial and computing power rails including 5 V, 12 V, and 24 V inputs. |
| Output Current | 8 A continuous - delivers high current density in compact 5 × 6 mm footprint without external MOSFETs. |
| Output Voltage Range | 0.8 V to 80% VIN - enables low-voltage core supplies (e.g., 1.8 V, 3.3 V) and adaptive scaling. |
| Switching Frequency | 200 kHz to 600 kHz - set by external RT resistor; higher frequencies allow smaller magnetics but increase switching loss. |
| Peak Efficiency | >95% - achieved via integrated low-RDS(ON) MOSFETs, synchronous rectification, and internal Schottky boost diode. |
| Operating Temperature | -40°C to +85°C - qualified for extended industrial environments and graphics card thermal profiles. |
| Protection Features | Over-current (latched after 16 cycles), over-voltage (2 consecutive cycles), under-voltage (16 cycles), thermal shutdown at ~155°C - ensures robust fault recovery in mission-critical loads. |
Pinout & Package
Package: 5 × 6 mm, 25-pin Molded Leadless Package (MLP) with three exposed thermal pads (P1, P2, P3) for enhanced heat dissipation. Thermal resistance junction-to-case is 4°C/W (P1/P3) and 7°C/W (P2).
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| SW (P1, 6–12) | Switching Node | Connects to inductor and high-side/low-side MOSFET drains; carries high di/dt; requires tight layout to minimize EMI and ringing. |
| VIN (P2, 2–5) | Main Input Supply | Accepts 3–24 V input; powers high-side gate drive and internal circuitry; decoupling capacitor must be placed near these pins. |
| PGND (P3, 21–23) | Power Ground Return | Low-impedance return path for Q2 source and power-stage currents; separate from AGND to avoid noise coupling. |
| BOOT (Pin 1) | High-Side Gate Drive Bootstrap | Connected via CBOOT to SW; internal bootstrap diode recharges capacitor when SW is low - eliminates need for external diode. |
| PGOOD (Pin 13) | Open-Drain Power-Good Flag | Pulls low when FB voltage deviates >±10% from 0.8 V reference; asserts high only after soft-start completes (T1.0). |
| EN (Pin 14) | Enable Control Input | Logic-high enable with internal 800 kΩ pull-up; toggling resets latched faults; discharge current sink (1 µA) enables auto-restart timing. |
| VCC (Pin 15) | Bias Supply Input | Requires ≥1.0 µF X5R/X7R capacitor to PGND; supplies IC logic, analog blocks, and gate drive energy (ICC ≈ 8–12 mA @ 600 kHz). |
| AGND (Pin 16) | Analog Ground Reference | Reference for FB, COMP, ILIM, R(T); must connect to low-noise ground island with minimal impedance to prevent control loop instability. |
| ILIM (Pin 17) | Current Limit Programming | Resistor to AGND sets trip threshold (12–18 A default); uses 10 µA current source - requires 1% tolerance resistor for accuracy. |
| R(T) (Pin 18) | Oscillator Frequency Setting | RT resistor to AGND determines fSW; 24 kΩ → 600 kHz, 50 kΩ → 300 kHz; open circuit prevents startup. |
| FB (Pin 19) | Feedback Voltage Input | Monitors output via resistor divider; internal 0.8 V reference with ±5 mV tolerance at 25°C; bias current -650 nA enables open-circuit detection. |
| COMP (Pin 20) | Error Amplifier Output | Drives external type-II or type-III compensation network between COMP and FB; output swing 0.4–3.2 V supports wide gain margin. |
| RAMP (Pin 25) | Voltage Feedforward Input | RRAMP resistor to VIN sets ramp amplitude for improved line transient response and duty-cycle stability across input range. |
| NC (Pin 24) | No Connect | Not internally bonded; must remain unconnected and unpopulated on PCB. |
Key Features
| Feature | Design Value |
|---|---|
| Integrated Synchronous MOSFETs | Eliminates external high- and low-side FETs and associated gate drivers - reduces BOM count and layout complexity while enabling 8 A in 5×6 mm. |
| Pre-Bias Startup | Allows safe startup into pre-charged output (e.g., hot-swap or multi-rail sequencing) without discharging downstream capacitance. |
| External Compensation Support | Enables precise loop tuning for diverse output capacitors (ceramic, polymer, electrolytic) and load transient requirements. |
| Programmable Current Limit | Adjustable over-current threshold via ILIM pin resistor - supports system-level current budgeting and fault containment. |
| Internal Soft-Start with Fault Inhibition | Gradual output ramp (5.3 ms to 0.8×VREF) prevents inrush; fault latch remains disabled until full ramp completion (6.7 ms), avoiding false trips. |
Applications
| Graphics Card VRM | Server Point-of-Load |
|---|---|
Use Scenario: Regulating GPU core voltage (e.g., 0.8–1.2 V) from 12 V rail under dynamic 0–8 A load transients. IC Role / Device Role / Timing Role: Primary synchronous buck controller with integrated power stage, providing fast transient response and thermal resilience in constrained space. Use Value: Delivers >95% efficiency at 8 A, minimizing heatsink size and airflow requirements while supporting PCIe hot-plug sequencing via pre-bias startup. | Use Scenario: Providing stable 3.3 V or 1.8 V supply to ASIC/FPGA I/O banks in 1U rack servers with strict thermal limits. IC Role / Device Role / Timing Role: High-density POL regulator with programmable frequency (300–500 kHz) to avoid noise coupling with clock domains and memory interfaces. Use Value: Enables compact, low-profile VRM design with ceramic output capacitors and no external MOSFET layout constraints - reducing board area by >40% vs discrete solutions. |
| Battery-Powered Test Equipment | Set-Top Box Power Management |
Use Scenario: Converting 12–24 V battery input to 5 V/3.3 V for portable oscilloscopes or signal analyzers requiring low-noise, stable supplies. IC Role / Device Role / Timing Role: Main DC-DC converter with wide-input capability and under-voltage lockout to prevent brownout during battery discharge. Use Value: Maintains regulation down to 3 V input and provides clean, ripple-free output with <±1% load regulation - critical for precision analog front-ends. | Use Scenario: Generating 1.2 V core and 3.3 V I/O rails from 12 V adapter input in consumer STB platforms with cost-sensitive BOM targets. IC Role / Device Role / Timing Role: Dual-rail POL solution leveraging single FAN2108EMPX per rail with shared layout and thermal management. Use Value: Reduces total solution cost by eliminating discrete controllers, MOSFETs, and gate drivers while meeting ENERGY STAR standby power requirements (<150 mW) via ultra-low shutdown current (7 µA). |
Equivalent & Alternatives
The following parts are listed as comparable options for similar synchronous buck regulator applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| MP2315DJ-LF-Z | 4 A max output, 4.5–26 V input, 20-pin QFN, no ILIM pin, fixed 500 kHz fSW | Suitable for lower-current loads; lacks programmable current limit and wide-frequency tuning. | Select when 4 A suffices and design simplicity outweighs flexibility; not drop-in due to lower current rating and missing ILIM/RT pins. |
| TPS54821RHLR | 8 A, 4.5–20 V input, 20-pin QFN, integrated MOSFETs, but requires external bootstrap capacitor and lacks internal Schottky diode. | Better suited for designs needing PMBus interface or tighter output voltage accuracy (±0.5%); higher BOM count due to external components. | Choose for TI ecosystem compatibility or digital monitoring needs; pinout and compensation differ significantly - redesign required. |
Compared with MP2315DJ-LF-Z and TPS54821RHLR, the FAN2108EMPX offers higher current (8 A), wider input (3–24 V), integrated Schottky boost diode, and true pre-bias startup - making it optimal for thermally constrained, high-transient POL applications where layout area and reliability are prioritized over digital control.
Availability
FAN2108EMPX is available at Aetrix Electronics and suitable for server power delivery, graphics card VRMs, and industrial embedded systems requiring stable component supply across extended temperature ranges (-40°C to +85°C).
Supply support for FAN2108EMPX 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
ON Semiconductor is a global semiconductor manufacturer specializing in power management, analog, sensor, and logic solutions for automotive, industrial, cloud, and IoT applications.
The FAN2108EMPX belongs to the TinyBuck™ family of integrated synchronous buck regulators, engineered for high-current, space-constrained point-of-load conversion in computing and graphics infrastructure where thermal performance and design simplicity are critical.
FAQ
What is the minimum input voltage supported by the FAN2108EMPX?
The FAN2108EMPX supports a minimum input voltage of 3 V, verified across its full -40°C to +85°C operating temperature range. This enables use with partially discharged 5 V or 12 V battery systems and low-voltage industrial rails. Below 3 V, the device enters under-voltage lockout and ceases switching - ensuring reliable start-up behavior without erratic operation.
Does the FAN2108EMPX require an external bootstrap diode?
No, the FAN2108EMPX does not require an external bootstrap diode. It integrates an internal synchronous bootstrap diode that recharges the BOOT capacitor when the SW node is low. This eliminates one external component, reduces layout area, and improves reliability - confirmed in the Pin Definitions section (Pin 1: BOOT) and Features list of the datasheet.
How is the output voltage programmed on the FAN2108EMPX?
The output voltage of the FAN2108EMPX is programmed using a resistor divider from VOUT to AGND, connected to the FB pin. With an internal 0.8 V reference and -650 nA bias current, the divider ratio sets VOUT = 0.8 V × (1 + R1/RBIAS). The datasheet provides Equation (3) for precise calculation, and typical circuits use 2.49 kΩ and 10 kΩ resistors for 1.8 V output - validated in Figure 10 and Circuit Description.
What protection features are built into the FAN2108EMPX?
The FAN2108EMPX includes over-current (latched after 16 pulse-by-pulse cycles), over-voltage (2 consecutive cycles), under-voltage (16 cycles), thermal shutdown (~155°C), and input under-voltage lockout (VCC UVLO at 4.3 V). All protections are active during normal operation and soft-start, and fault recovery is managed via EN pin discharge/recharge or VCC cycling - detailed in Sections 5 and 12 of the datasheet.
Can the FAN2108EMPX start up into a pre-biased output?
Yes, the FAN2108EMPX supports pre-bias startup, explicitly stated in the Features list and Circuit Description. It prevents output discharge during startup by inhibiting low-side MOSFET conduction until the internal soft-start ramp reaches ~0.76 V, avoiding negative voltage undershoot. This behavior is validated in Figure 16 (Startup with 1 V Pre-Bias) and enables safe integration in multi-rail or hot-swap systems.
FAN2108EMPX Specifications
- Product attributes
- Attribute value
- Manufacturer:
- onsemi
- Series:
- TinyBuck®
- Package/Case:
- 25-WQFN Exposed Pad
- Packaging:
- Tape & Reel (TR)
- Product Status:
- Obsolete
- Function:
- Step-Down
- Output Configuration:
- Positive
- Topology:
- Buck
- Output Type:
- Adjustable
- Number of Outputs:
- 1
- Voltage - Input (Min):
- 3V
- Voltage - Input (Max):
- 24V
- Voltage - Output (Min/Fixed):
- 0.8V
- Voltage - Output (Max):
- 19.2V
- Current - Output:
- 8A
- Frequency - Switching:
- 300kHz ~ 600kHz
- Synchronous Rectifier:
- Yes
- Operating Temperature:
- -40°C ~ 85°C (TA)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 25-MLP (6x5)
FAN2108EMPX FAQ
1.How can I place an order for FAN2108EMPX through Aetrix?
Please submit a Request for Quotation (RFQ) for FAN2108EMPX 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 FAN2108EMPX reliable?
The price and inventory of FAN2108EMPX are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for FAN2108EMPX is usually 5 days.
3.What payment methods are accepted for FAN2108EMPX?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for FAN2108EMPX transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for FAN2108EMPX?
FAN2108EMPX orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your FAN2108EMPX 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 FAN2108EMPX?
For technical support, including FAN2108EMPX datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your FAN2108EMPX requirements.
6.How does Aetrix verify that FAN2108EMPX is sourced from the original manufacturer or authorized distributors?
All FAN2108EMPX 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 FAN2108EMPX meets industry standards.
7.What is the process for return or replacement of FAN2108EMPX?
All FAN2108EMPX units undergo pre-shipment inspection (PSI). If there is an issue with FAN2108EMPX, 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 FAN2108EMPX part is unused and in its original packaging.
Return procedure for FAN2108EMPX:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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