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Home > Products > Integrated Circuits (ICs) > Power Management (PMIC) > Voltage Regulators - DC DC Switching Regulators

onsemi FAN5307S18X

Name: FAN5307S18X
Brand: onsemi
SKU: FAN5307S18X
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: FAN5307S18X

Manufacturer:: onsemi

Category:: Voltage Regulators - DC DC Switching Regulators

Package:: SC-74A, SOT-753

Datasheet:: FAN5307S18X.pdf

Description:: IC REG BUCK 1.8V 300MA SOT23-5

Quantity:: RFQ Add To RFQ list

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Product details

Overview

FAN5307S18X from Fairchild Semiconductor is a high-efficiency, synchronous step-down DC-DC converter delivering 1.8 V at up to 300 mA output current, operating from 2.5 V to 5.5 V input, with 1 MHz fixed-frequency PWM and power-save (PFM) mode, designed for battery-powered portable electronics.

For engineers reviewing the FAN5307S18X datasheet, pinout, applications, or equivalent options, this device offers verified 15 µA quiescent current in Power-Save mode, ±4% output voltage accuracy over temperature and load, 100% duty-cycle low-dropout operation, dynamic voltage positioning for transient headroom, and SOT-23-5 package compatibility for space-constrained designs.

Technical Context

The FAN5307S18X employs current-mode PWM control with automatic transition to pulse-frequency modulation (PFM) below ~80 mA load, enabling high efficiency across light-to-heavy loads. Its internal 0.5 V reference and fixed 1.8 V output eliminate external feedback resistors.

It integrates P-channel and N-channel MOSFETs with typical R_DS(on) of 690 mΩ (P) and 540 mΩ (N) at 3.6 V, supports 100% duty cycle operation near V_IN ≈ V_OUT, and features digital soft-start limiting inrush current with ~500 µs typical startup time into 10 µF C_OUT.

Key Specifications

Parameter	Value and Actual Design Meaning
Output Voltage	Fixed 1.8 V ±4% over -40°C to +85°C, eliminating external resistor divider and reducing BOM count.
Input Voltage Range	2.5 V to 5.5 V - supports single-cell Li-ion (3.0–4.2 V), Li-polymer, and dual-cell alkaline/NiMH systems.
Max Output Current	300 mA continuous - sufficient for core logic rails in portable microcontrollers and low-power DSPs.
Switching Frequency	1 MHz ±20% - enables use of compact 10 µH inductors and 10 µF ceramic output capacitors.
Quiescent Current	15 µA in Power-Save mode - extends battery runtime in standby/sleep states of handheld devices.
Efficiency Peak	95% at 200 mA / 3.6 V_IN - minimizes thermal rise and power loss in thermally constrained enclosures.
Load Regulation	0.0022% / mA (SOT-23) - ensures stable 1.8 V supply under dynamic load steps typical in digital baseband ICs.

Pinout & Package

Package: 5-Lead SOT-23 (JEDEC MO-178, variation AA), 2.9 mm × 1.6 mm × 1.1 mm body, exposed pad not present.

Pin/Terminal	Circuit Role	Design Meaning
1 - VIN	Supply Input	Accepts 2.5–5.5 V; requires ≥4.7 µF low-ESR ceramic capacitor placed adjacent to pin for stability.
2 - GND	Reference Ground	Common return for feedback amplifier and control logic; must be connected to low-impedance ground plane.
3 - EN	Enable Input	Active-high logic interface; <1 µA shutdown current when pulled low; must not be left floating.
4 - FB	Feedback Input	Internally tied to 1.8 V output; no external resistor required - simplifies layout and improves noise immunity.
5 - LX	Switch Node	Connects to inductor and internal P/N-MOSFET switches; high di/dt node requiring short, wide trace routing.

Key Features

Feature	Design Value
Synchronous Rectification	Integrated P/N-MOSFETs reduce conduction losses vs. external diode solutions, enabling >90% efficiency at 10 mA.
Dynamic Voltage Positioning	Shifts output +0.8% during light-load PFM mode to provide headroom against load transients, minimizing undershoot.
100% Duty-Cycle Operation	Maintains regulation down to V_IN − V_OUT ≈ I_LOAD × R_DS(on), critical for Li-ion discharge tail-end performance.
Digital Soft-Start	Four-step current ramp limits inrush; achieves 500 µs typical startup into 200 mA load without input droop or overshoot.
Cycle-by-Cycle Current Limit	Internal 520 mA peak switch current limit provides robust short-circuit protection without external sensing components.

Applications

Pocket PC Core Rail	Cell Phone Baseband Supply
Use Scenario: Powers ARM9/ARM11 application processors and SRAM in sub-500 g handheld PDAs with single-cell Li-ion battery. IC Role / Device Role / Timing Role: Primary 1.8 V core regulator delivering clean, dynamically responsive power to CPU and memory subsystems. Use Value: Dynamic voltage positioning prevents brownout during burst processing; 15 µA quiescent current extends idle battery life by >30% vs. legacy LDOs.	Use Scenario: Supplies 1.8 V to GSM/GPRS baseband ICs during transmit/receive cycles with rapid 0–300 mA load transitions. IC Role / Device Role / Timing Role: High-transient-response buck converter maintaining regulation during RF power amplifier switching events. Use Value: <10 µs load transient recovery time and ±4% output accuracy ensure reliable digital logic timing margins under RF interference.
Digital Camera Image Sensor Bias	Low-Power DSP Core Supply
Use Scenario: Provides regulated 1.8 V to CMOS image sensor analog front-end and column ADC during exposure readout. IC Role / Device Role / Timing Role: Low-noise, fast-settling power source for precision analog signal chain elements. Use Value: 1 MHz switching frequency places noise beyond sensitive analog bandwidth; <1% output ripple preserves SNR in 12-bit imaging pipelines.	Use Scenario: Powers TI TMS320C55x or ADI SHARC DSP cores in portable audio recorders and voice-enabled IoT edge nodes. IC Role / Device Role / Timing Role: Efficient, compact DC-DC solution replacing discrete buck controllers and external MOSFETs. Use Value: SOT-23-5 footprint saves >40% PCB area vs. controller+MOSFET solutions; integrated current limit eliminates external sense resistor.

Pocket PC Core Rail

Cell Phone Baseband Supply

Use Scenario: Powers ARM9/ARM11 application processors and SRAM in sub-500 g handheld PDAs with single-cell Li-ion battery.

IC Role / Device Role / Timing Role: Primary 1.8 V core regulator delivering clean, dynamically responsive power to CPU and memory subsystems.

Use Value: Dynamic voltage positioning prevents brownout during burst processing; 15 µA quiescent current extends idle battery life by >30% vs. legacy LDOs.

Use Scenario: Supplies 1.8 V to GSM/GPRS baseband ICs during transmit/receive cycles with rapid 0–300 mA load transitions.

IC Role / Device Role / Timing Role: High-transient-response buck converter maintaining regulation during RF power amplifier switching events.

Use Value: <10 µs load transient recovery time and ±4% output accuracy ensure reliable digital logic timing margins under RF interference.

Digital Camera Image Sensor Bias

Low-Power DSP Core Supply

Use Scenario: Provides regulated 1.8 V to CMOS image sensor analog front-end and column ADC during exposure readout.

IC Role / Device Role / Timing Role: Low-noise, fast-settling power source for precision analog signal chain elements.

Use Value: 1 MHz switching frequency places noise beyond sensitive analog bandwidth; <1% output ripple preserves SNR in 12-bit imaging pipelines.

Use Scenario: Powers TI TMS320C55x or ADI SHARC DSP cores in portable audio recorders and voice-enabled IoT edge nodes.

IC Role / Device Role / Timing Role: Efficient, compact DC-DC solution replacing discrete buck controllers and external MOSFETs.

Use Value: SOT-23-5 footprint saves >40% PCB area vs. controller+MOSFET solutions; integrated current limit eliminates external sense resistor.

Equivalent & Alternatives

The following parts are listed as comparable options for similar step-down DC-DC converter applications.

Alternative Part	Technical Difference	Application Difference	Selection Advice
Texas Instruments TPS62231DRYR	1.8 V fixed, 300 mA, 2.05–6.0 V input, 3 MHz switching, 22 µA IQ, 6-pin WSON (2×2 mm).	Higher frequency allows smaller magnetics but increases EMI sensitivity; no dynamic voltage positioning.	Preferred where board space is tighter and higher-frequency filtering is feasible; not drop-in due to different pinout and package.
Analog Devices ADP2105ACBZ-1.8-R7	1.8 V fixed, 300 mA, 2.3–5.5 V input, 3 MHz, 25 µA IQ, 6-pin WLCSP (1.28×1.28 mm).	Smaller WLCSP package requires microvia routing; lacks 100% duty-cycle mode and soft-start programmability.	Selected for ultra-compact wearables; requires redesign for thermal relief and solder mask-defined pads.

Compared with FAN5307S18X, the TPS62231DRYR offers higher switching frequency but sacrifices transient headroom control, while the ADP2105ACBZ-1.8-R7 reduces footprint at the cost of thermal dissipation capability and startup behavior - making FAN5307S18X optimal for cost-sensitive, thermally constrained portable designs needing proven light-load efficiency and robust transient response.

Availability

FAN5307S18X is available at Aetrix Electronics and suitable for pocket PCs, cell phones, and digital cameras requiring stable component supply, long-term lifecycle support, and RoHS-compliant packaging in tape-and-reel format.

Supply support for FAN5307S18X 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

Fairchild Semiconductor was a U.S.-based semiconductor company specializing in power management, analog, and discrete components before its acquisition by ON Semiconductor in 2016; its legacy products remain widely deployed in industrial and consumer systems.

The FAN5307 series was developed specifically for battery-powered portable electronics demanding high light-load efficiency, small footprint, and seamless mode transition - targeting design-in longevity in handheld computing and communications devices.

FAQ

What is the recommended input and output capacitor configuration for FAN5307S18X?

The FAN5307S18X requires a minimum 4.7 µF low-ESR ceramic input capacitor placed adjacent to the VIN pin and a 10 µF ceramic output capacitor. Recommended values are 4.7 µF (e.g., Taiyo Yuden JMK212BY475MG) at input and 10–22 µF (e.g., TDK C3216X5ROJ106M) at output. These values ensure stable 1 MHz operation, minimize voltage ripple, and support fast load transient response per the datasheet's Figure 6 and Table 2.

Does FAN5307S18X require external feedback resistors to set the output voltage?

No, FAN5307S18X does not require external feedback resistors. It is a fixed 1.8 V output variant with internal feedback network connecting the FB pin directly to the regulated output. This eliminates resistor tolerance errors, reduces component count, and improves noise immunity compared to adjustable versions like FAN5307SX. The FB pin must be connected to VOUT per the pin definition in the datasheet.

What is the shutdown current and enable logic behavior of FAN5307S18X?

FAN5307S18X draws less than 1 µA shutdown current when the EN pin is pulled low. The EN pin is active-high with V_ENH = 1.3 V (min) and V_ENL = 0.5 V (max); it must never be left floating. If tied to VIN, the input supply must ramp at >5 V/ms to ensure proper regulation startup. This behavior is confirmed in the "Pin Definitions" section (page 3) and Electrical Characteristics table (page 5) of the FAN5307 Rev. 1.0.5 datasheet.

How does FAN5307S18X handle load transients, and what is its typical recovery time?

FAN5307S18X uses current-mode control and dynamic voltage positioning to achieve excellent load transient response: output voltage deviation is limited to ±30 mV for 0–300 mA steps (per Figure 6), with recovery settling within 10–20 µs. The 0.8% PFM-mode voltage boost provides headroom, while the 1 MHz PWM loop ensures fast correction. This performance is validated across -40°C to +85°C and supports real-time baseband and imaging workloads.

Is FAN5307S18X compatible with 10 µH inductors, and what is the maximum recommended DC resistance?

Yes, FAN5307S18X is optimized for 10 µH inductors, as specified in the Recommended Operating Conditions (page 4) and Application Information (page 10). The maximum recommended DC resistance is ≤150 mΩ to maintain >90% efficiency at 300 mA. Inductors such as Sumida CDRH5D28-100 or Murata LQH66SN100M01L meet this requirement and are listed in Table 1 of the datasheet for highest efficiency implementation.

FAN5307S18X Specifications

Product attributes: Attribute value

Manufacturer:: onsemi

Series:: -

Package/Case:: SC-74A, SOT-753

Packaging:: Tape & Reel (TR)

Product Status:: Obsolete

Function:: Step-Down

Output Configuration:: Positive

Topology:: Buck

Output Type:: Fixed

Number of Outputs:: 1

Voltage - Input (Min):: 2.5V

Voltage - Input (Max):: 5.5V

Voltage - Output (Min/Fixed):: 1.8V

Voltage - Output (Max):: -

Current - Output:: 300mA

Frequency - Switching:: 1MHz

Synchronous Rectifier:: Yes

Operating Temperature:: -40°C ~ 85°C (TA)

Grade:: -

Qualification:: -

Mounting Type:: Surface Mount

Supplier Device Package:: SOT-23-5

FAN5307S18X FAQ

1.How can I place an order for FAN5307S18X through Aetrix?

Please submit a Request for Quotation (RFQ) for FAN5307S18X 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 FAN5307S18X reliable?

The price and inventory of FAN5307S18X are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for FAN5307S18X is usually 5 days.

3.What payment methods are accepted for FAN5307S18X?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for FAN5307S18X transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for FAN5307S18X?

FAN5307S18X orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your FAN5307S18X 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 FAN5307S18X?

For technical support, including FAN5307S18X datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your FAN5307S18X requirements.

6.How does Aetrix verify that FAN5307S18X is sourced from the original manufacturer or authorized distributors?

All FAN5307S18X 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 FAN5307S18X meets industry standards.

7.What is the process for return or replacement of FAN5307S18X?

All FAN5307S18X units undergo pre-shipment inspection (PSI). If there is an issue with FAN5307S18X, 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 FAN5307S18X part is unused and in its original packaging.

Return procedure for FAN5307S18X:

1.Submit a request within 90 days.

2.Obtain a Return Material Authorization (RMA) from Aetrix.

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