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onsemi FAN4855MTC
- Part No.:
- FAN4855MTC
- Manufacturer:
- onsemi
- Package:
- 8-TSSOP (0.173", 4.40mm Width)
- Datasheet:
-
FAN4855MTC.pdf
- Description:
- IC REG BOOST ADJ 500MA 8TSSOP
- Quantity:
- Payment:
- Shipping:
Inventory:2,284
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Product details
Overview
FAN4855MTC from Fairchild Semiconductor is a 500mA synchronous boost regulator with adjustable output (3V–5V), low-battery detection, and logic-controlled shutdown. It operates from 1.6V–4.5V input, achieves 95% efficiency at 200mA load, and features internal NFET/PFET switches with 0.35Ω ON resistance. Used in portable Li-Ion and multi-cell alkaline systems for powering 3.3V/5V peripherals.
For engineers reviewing the FAN4855MTC datasheet, pinout, applications, or equivalent options, key selection criteria include startup voltage (1.35V), quiescent current (80µA), feedback reference (1.243V), LBI threshold (0.39V), and TSSOP-8 thermal resistance (124°C/W).
Technical Context
The FAN4855MTC uses variable on-time Pulse Frequency Modulation (PFM) without an oscillator, enabling load-dependent switching up to 430kHz. Its control architecture transitions between discontinuous and continuous conduction modes to maintain high efficiency across light-to-heavy loads.
It integrates synchronous rectification via internal PFET Q2, eliminating external diode losses. The error amplifier compares FB voltage against 1.243V reference, triggering NMOS Q1 gate pulses whose duration scales with VIN to stabilize inductor ripple current and maximize conversion efficiency.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 1.6V to 4.5V - supports single-cell Li-Ion (2.7–4.2V) and 2–3 AA/AAA (2.4–4.5V) operation |
| Output Voltage Range | 3.0V to 5.0V - adjustable via external resistor divider; nominal 3.3V or 5V outputs |
| Max Output Current | 500mA at VOUT=3.3V/VIN=2.5V - sufficient for LCD bias, SD card, or USB peripheral rails |
| Peak Efficiency | 95% at ILOAD=200mA, VIN=3V, VOUT=3.3V - reduces thermal stress and extends battery runtime |
| Feedback Reference | 1.243V ±1.5% - sets output accuracy; enables precise VOUT programming with ≤0.1% resistor tolerance |
| LBI Threshold | 0.390V ±25mV - triggers LBO active-low flag when scaled battery voltage drops below setpoint |
| Quiescent Current | 80µA typical - minimizes standby drain in always-on subsystems like real-time clocks |
| Shutdown Current | <10µA - isolates load from input and disables internal comparators to maximize shelf life |
Pinout & Package
Package: 8-pin TSSOP (T08), 3.0mm × 4.4mm footprint, 1.2mm height, 124°C/W θJA.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| VIN | Battery input supply | Supplies IC during startup; after regulation, IC draws power from VOUT - enables ultra-low VIN start (1.35V) |
| SHDN | Logic shutdown control | Active-low enable; pulls below ~0.5×VIN to halt switching and disconnect load - true-load disconnect prevents backfeed |
| LBI | Low-battery comparator input | Accepts scaled-down battery voltage; threshold fixed at 0.39V - requires external resistive divider for VIN_MIN programming |
| LBO | Open-drain low-battery alert | Active-low flag; sinks ≥1mA at 0.2V - used to reset microcontrollers or trigger system sleep mode |
| FB | Feedback node | Connects to resistor divider midpoint; regulates VOUT by comparing to 1.243V reference - sets output accuracy and stability |
| VOUT | Regulated output rail | Delivers up to 500mA at 3–5V; supplies downstream circuitry - must be decoupled with ≥47µF tantalum + 18pF ceramic |
| VL | Boost inductor switch node | Drives external 10µH inductor; integrates NMOS Q1 and PFET Q2 - synchronous rectification eliminates external diode |
| GND | Power and signal ground | Reference for all voltages; star-ground connection to output capacitor cathode minimizes noise coupling |
Key Features
| Feature | Design Value |
|---|---|
| Synchronous rectification | Integrated PFET replaces external Schottky diode - eliminates 0.3–0.5V forward drop, improving light-load efficiency by >10% |
| Variable on-time PFM | No oscillator required; switching frequency varies with load - reduces switching losses at light loads, maintaining >85% efficiency down to 1mA |
| True-load disconnect | SHDN asserts internal isolation FET - prevents reverse current flow into depleted battery, protecting cell health |
| Low-battery detection | Dedicated LBI/LBO comparator with 25mV hysteresis - provides reliable undervoltage warning without MCU intervention |
| Ultra-low quiescent current | 80µA operating / <10µA shutdown - extends battery life in intermittently active devices like remote controls or sensors |
Applications
| Digital Still Cameras (DSCs) | Personal Digital Assistants (PDAs) |
|---|---|
Use Scenario: Powering CCD/CMOS image sensor bias rails and LCD backlight drivers from 2-cell alkaline batteries. IC Role / Device Role / Timing Role: Primary DC-DC boost converter generating stable 5V rail from declining 2.4–3.0V input. Use Value: Maintains consistent sensor performance and display brightness across full battery discharge curve with no manual voltage adjustment. | Use Scenario: Supplying 3.3V logic and memory interface rails in handheld PDAs powered by single-cell Li-Ion. IC Role / Device Role / Timing Role: Adjustable-output boost regulator enabling flexible system voltage scaling as SoC requirements evolve. Use Value: Supports both 3.3V and 5V peripheral interfaces using same BOM, reducing design variants and inventory complexity. |
| Smartphones & Feature Phones | Portable Instrumentation |
Use Scenario: Generating auxiliary 5V rail for USB OTG functionality or camera flash charging from main 3.7V Li-Ion battery. IC Role / Device Role / Timing Role: Secondary boost stage with shutdown control synchronized to host processor activity. Use Value: Enables USB host capability without compromising standby time - SHDN cuts leakage to <10µA when OTG inactive. | Use Scenario: Providing isolated 3.3V supply for precision ADC reference and analog front-end in battery-powered multimeters. IC Role / Device Role / Timing Role: Low-noise, high-accuracy boost regulator with tight line/load regulation (≤2%). Use Value: Ensures measurement stability across varying battery voltage (1.6–4.5V), eliminating calibration drift due to supply variation. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar boost regulator applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| TPS61022DRVR | Higher 2A output, 93% peak efficiency, 0.65V startup, but requires external MOSFET and diode - no integrated synchronous rectifier | Targets higher-power applications like portable projectors; lacks built-in LBI/LBO comparator | Choose TPS61022DRVR only if >500mA load or sub-1.3V startup is required; FAN4855MTC offers simpler BOM and integrated protection |
| MAX8632EUB+ | Fixed 3.3V output, 600mA rating, 94% efficiency, 1.8V min input - no adjustable output or low-battery detect | Suitable for cost-sensitive, fixed-voltage designs where flexibility is not needed | Select MAX8632EUB+ only for production runs requiring lowest unit cost and fixed 3.3V output; FAN4855MTC provides design reuse across multiple VOUT targets |
Compared with TPS61022DRVR and MAX8632EUB+, the FAN4855MTC delivers optimal balance of integration (synchronous rectifier, LBI/LBO, adjustable VOUT), ultra-low quiescent current (80µA), and proven reliability in space-constrained portable systems - making it ideal for DSCs, PDAs, and instrumentation where BOM count and battery life are critical.
Availability
FAN4855MTC is available at Aetrix Electronics and suitable for digital still cameras, portable instrumentation, and single-cell Li-Ion operated devices requiring stable component supply, long-term lifecycle support, and traceable sourcing.
Supply support for FAN4855MTC 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 analog and power IC manufacturer acquired by ON Semiconductor in 2016; known for high-performance power management and discrete solutions.
The FAN4855MTC belongs to Fairchild's low-power DC-DC converter product line, designed specifically for battery-powered portable electronics requiring high efficiency, small footprint, and integrated protection features.
FAQ
What is the minimum input voltage required for FAN4855MTC to start up?
The FAN4855MTC starts up at 1.35V under light load conditions (ILOAD < 1mA). After startup, it continues regulating down to 1.0V input while delivering rated output. This ultra-low startup voltage enables use with deeply discharged 2-cell alkaline or NiMH batteries, extending usable battery life beyond conventional boost regulators that require ≥1.8V.
How does the FAN4855MTC achieve 95% efficiency without an external diode?
The FAN4855MTC achieves 95% efficiency through integrated synchronous rectification: an internal PFET replaces the traditional Schottky diode, eliminating its 0.3–0.5V forward voltage drop. During flyback, the synchronous rectifier control circuit actively drives the PFET gate, reducing conduction loss and enabling high efficiency even at light loads - a key advantage over asynchronous boost converters.
Can the FAN4855MTC be used to drive white LEDs directly?
Yes, the FAN4855MTC can drive white LEDs in constant-current configuration by replacing the feedback resistor divider with a current-sense resistor and LED string. Application Example 11 in the datasheet demonstrates this using four 62Ω series resistors to regulate LED current at ~19mA over 0–5V input range - leveraging the FAN4855MTC's accurate feedback reference and stable regulation.
What is the purpose of the LBI and LBO pins on the FAN4855MTC?
The LBI (Low-Battery Input) and LBO (Low-Battery Output) pins implement a dedicated undervoltage detection circuit. LBI accepts a scaled-down battery voltage; when it falls below 0.39V, LBO asserts an open-drain active-low signal. This allows the FAN4855MTC to autonomously warn the system of low battery without MCU polling - commonly used to trigger graceful shutdown or enter low-power sleep mode.
Is the FAN4855MTC pin-compatible with other Fairchild boost regulators?
No, the FAN4855MTC has a unique 8-pin TSSOP pinout optimized for its integrated synchronous topology and dual-comparator functions. It is not pin-compatible with earlier Fairchild boost ICs like FAN5331 or FAN5333, which use different pin assignments for SHDN, FB, and VL. PCB layout must follow the FAN4855MTC-specific pin configuration shown in Figure 2 of the datasheet.
FAN4855MTC Specifications
- Product attributes
- Attribute value
- Manufacturer:
- onsemi
- Series:
- -
- Package/Case:
- 8-TSSOP (0.173", 4.40mm Width)
- Packaging:
- Tube
- Product Status:
- Obsolete
- Function:
- Step-Up
- Output Configuration:
- Positive
- Topology:
- Boost
- Output Type:
- Adjustable
- Number of Outputs:
- 1
- Voltage - Input (Min):
- 1.6V
- Voltage - Input (Max):
- 4.5V
- Voltage - Output (Min/Fixed):
- 3V
- Voltage - Output (Max):
- 5V
- Current - Output:
- 500mA (Switch)
- Frequency - Switching:
- -
- Synchronous Rectifier:
- Yes
- Operating Temperature:
- -40°C ~ 85°C (TA)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 8-TSSOP
FAN4855MTC FAQ
1.How can I place an order for FAN4855MTC through Aetrix?
Please submit a Request for Quotation (RFQ) for FAN4855MTC 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 FAN4855MTC reliable?
The price and inventory of FAN4855MTC are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for FAN4855MTC is usually 5 days.
3.What payment methods are accepted for FAN4855MTC?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for FAN4855MTC transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for FAN4855MTC?
FAN4855MTC orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your FAN4855MTC 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 FAN4855MTC?
For technical support, including FAN4855MTC datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your FAN4855MTC requirements.
6.How does Aetrix verify that FAN4855MTC is sourced from the original manufacturer or authorized distributors?
All FAN4855MTC 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 FAN4855MTC meets industry standards.
7.What is the process for return or replacement of FAN4855MTC?
All FAN4855MTC units undergo pre-shipment inspection (PSI). If there is an issue with FAN4855MTC, 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 FAN4855MTC part is unused and in its original packaging.
Return procedure for FAN4855MTC:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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