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onsemi FAN4855MTCX
- Part No.:
- FAN4855MTCX
- Manufacturer:
- onsemi
- Package:
- 8-TSSOP (0.173", 4.40mm Width)
- Datasheet:
-
FAN4855MTCX.pdf
- Description:
- IC REG BOOST ADJ 500MA 8TSSOP
- Quantity:
- Payment:
- Shipping:
Inventory:4,374
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Product details
Overview
FAN4855MTCX from Fairchild Semiconductor is a 500mA synchronous boost DC-DC regulator with adjustable output (3V–5V), low-battery detection, and logic-controlled shutdown. It operates from 1.6V–4.5V input, achieves 95% peak efficiency, starts up at 1.35V, and delivers regulated power for portable Li-Ion and multi-cell alkaline systems.
For engineers reviewing the FAN4855MTCX datasheet, pinout, applications, or equivalent options, key selection criteria include its PFM control architecture, internal synchronous rectifier eliminating external diode, 80µA quiescent current, TSSOP-8 package footprint, and integrated low-battery comparator with 0.39V threshold.
Technical Context
The FAN4855MTCX uses variable on-time Pulse Frequency Modulation (PFM) without an oscillator, enabling load-dependent switching frequency up to 430kHz. Its constant-peak-current limit (0.8A) and minimum off-time logic (≥1µs) allow seamless transition between discontinuous and continuous conduction modes across light-to-heavy loads.
It integrates dual N-channel MOSFETs - one as main switch (Q1), the other as synchronous rectifier (Q2) - controlled by dedicated SRC circuitry. Feedback regulation relies on a 1.243V reference applied to the FB pin via external resistor divider, while LBI/LBO pins implement open-drain low-battery alert with 25mV hysteresis and true-load disconnect during shutdown.
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) without pre-regulation. |
| Output Voltage Range | 3.0V to 5.0V - adjustable via external resistive divider; nominal 3.3V or 5V outputs confirmed in test circuits. |
| Max Output Current | 500mA at VOUT=3.3V/VIN=2.5V - sufficient for LCD bias, memory I/O, or RF front-end supply in portable devices. |
| Peak Efficiency | 95% at ILOAD=200mA, VIN=3V, VOUT=3.3V - enabled by synchronous rectification and optimized gate drive timing. |
| Quiescent Current | 80µA typical - minimizes standby drain in battery-powered systems with intermittent operation. |
| Start-Up Voltage | 1.35V typical - allows operation down to deeply discharged single-cell Li-Ion or two alkaline cells. |
| Feedback Reference | 1.243V - precise internal reference enables ±1.5% output voltage accuracy over temperature and line/load conditions. |
Pinout & Package
Package: 8-pin TSSOP (T08), 3.0mm × 4.4mm body, 0.65mm pitch, exposed pad not specified.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| VIN | Battery input supply | Primary power source; supplies IC during start-up and powers VL switch node via external inductor. |
| SHDN | Logic shutdown control | Active-low enable; pulls below ~0.5×VIN to halt switching and disconnect load from input path. |
| LBI | Low-battery sense input | Analog input referenced to 0.39V threshold; accepts scaled battery voltage via external resistor divider. |
| LBO | Low-battery open-drain output | Active-low flag; requires external pull-up to VOUT (e.g., 100kΩ) to signal microcontroller reset or UI alert. |
| FB | Feedback voltage sensing | Connects to resistor divider midpoint; regulates output by comparing against 1.243V internal reference. |
| VOUT | Regulated boost output | Delivers up to 500mA; connects to output capacitor and load; supplies internal circuitry after start-up. |
| VL | Switch node connection | Drives external boost inductor; internal NMOS switch connects VIN to VL during on-time; synchronous rectifier discharges energy to VOUT. |
| GND | Power and signal ground | Common return for all internal blocks; must be star-connected near output capacitor for EMI and regulation stability. |
Key Features
| Feature | Design Value |
|---|---|
| Synchronous rectification | Eliminates external Schottky diode, reducing conduction loss and board area; improves light-load efficiency. |
| Variable on-time PFM control | Enables ultra-low quiescent current (80µA) and high efficiency (>90%) across 0.1–500mA load range. |
| True-load disconnect in shutdown | Isolates output from input during SHDN assertion, preventing reverse current and preserving battery charge. |
| Integrated low-battery detector | Provides system-level battery monitoring with 0.39V threshold and 25mV hysteresis - no external comparator needed. |
| Start-up at 1.35V | Enables operation from partially depleted batteries, extending usable runtime in portable instrumentation and DSCs. |
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 or Li-Ion battery. IC Role / Device Role / Timing Role: Primary boost regulator delivering stable 3.3V/5V output with fast transient response to handle burst-mode sensor readout. Use Value: Synchronous rectification and PFM control maintain >92% efficiency at 10–100mA loads, extending capture count per battery charge. | Use Scenario: Supplying 3.3V logic core and 5V USB interface from single-cell Li-Ion battery in handheld organizer. IC Role / Device Role / Timing Role: Adjustable-output DC-DC converter with shutdown control synchronized to host processor sleep states. Use Value: 80µA quiescent current and <10µA shutdown current minimize standby drain, enabling weeks of calendar sync without recharge. |
| Smartphones & Feature Phones | Portable Instrumentation |
Use Scenario: Generating 5V USB OTG power or camera flash LED driver supply from 3.7V Li-Ion cell. IC Role / Device Role / Timing Role: High-efficiency boost stage with programmable low-battery alert tied to system PMIC interrupt line. Use Value: Integrated LBO provides accurate battery state-of-charge signaling without additional BOM cost or layout space. | Use Scenario: Providing isolated 5V analog front-end supply for handheld multimeters or gas detectors powered by 3×AAA cells. IC Role / Device Role / Timing Role: Input-voltage-flexible regulator operating from 3.0–4.5V battery stack with robust start-up down to 1.35V. Use Value: Wide input range and 1.35V start-up ensure reliable operation even with aging alkaline cells, reducing field failure rate. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar boost regulator applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| TPS61022DRCT | Higher 2A output capability; fixed 5V output only; 2.5V min input; no integrated LBO. | Requires external battery monitor; better suited for high-current USB PD accessories than low-power portable UI. | Select when >500mA load or fixed 5V simplifies design; avoid if adjustable output or battery alert is required. |
| MAX17065ETA+ | 3.3V/5V selectable output; 1.8V min input; includes I²C interface for dynamic voltage scaling; no LBO. | Supports firmware-controlled output adjustment but adds communication overhead and external pull-ups. | Choose for programmable systems needing runtime voltage optimization; not ideal for cost-sensitive, standalone battery-powered devices. |
Compared with TPS61022DRCT and MAX17065ETA+, the FAN4855MTCX offers unique integration of adjustable output, low-battery detection, and true-load disconnect in a minimal 8-pin TSSOP - making it optimal for space-constrained, battery-life-critical portable designs where external monitoring is undesirable.
Availability
FAN4855MTCX is available at Aetrix Electronics and suitable for digital still cameras, PDAs, and portable instrumentation requiring stable component supply, long-term lifecycle support, and consistent parametric performance across production batches.
Supply support for FAN4855MTCX 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 FAN4855 belongs to Fairchild's low-power DC-DC converter product line, designed specifically for battery-operated portable electronics demanding high efficiency, small footprint, and integrated system supervision functions.
FAQ
What is the minimum input voltage required for the FAN4855MTCX to start switching?
The FAN4855MTCX starts switching at a typical input voltage of 1.35V under light load (<1mA), with guaranteed operation down to 1.6V per recommended conditions. This enables use with deeply discharged single-cell Li-Ion or two alkaline cells. The FAN4855MTCX continues regulating down to 1.0V after startup, supporting extended battery runtime in portable applications.
Does the FAN4855MTCX require an external diode for boost operation?
No, the FAN4855MTCX does not require an external diode because it integrates a synchronous rectifier (Q2) that replaces the traditional Schottky diode. During the flyback phase, the internal PFET shorts its body diode, reducing conduction loss and improving efficiency - especially critical at light loads where diode forward voltage dominates losses. This eliminates BOM cost and PCB area associated with external diodes.
How is the output voltage set on the FAN4855MTCX?
The output voltage of the FAN4855MTCX is set using an external resistor divider connected between VOUT, FB, and GND. The FB pin senses the divided voltage and compares it to the internal 1.243V reference. To achieve a target VOUT, select R5 ≤ 270kΩ and calculate R4 = R5 × (VOUT / 1.24 − 1). For example, for 3.3V output with R5 = 240kΩ, R4 ≈ 390kΩ.
What is the function of the LBI and LBO pins on the FAN4855MTCX?
The LBI (Low-Battery Input) pin accepts a scaled-down battery voltage via external resistor divider; when this voltage falls below 0.39V, the LBO (Low-Battery Output) pin pulls low as an open-drain signal. The FAN4855MTCX uses this to generate a system-level battery alert - e.g., triggering MCU reset or UI warning. LBO is active only when the device is enabled; during shutdown, LBO enters high-impedance state.
Can the FAN4855MTCX drive white LEDs directly?
Yes, the FAN4855MTCX can drive white LEDs in constant-current configuration by replacing the feedback resistor divider with a current-sense resistor and LED string. Application Note AN-6022 demonstrates this using the FAN4855MTCX with four 62Ω series resistors to deliver ~19mA LED current across 0–5V input. This leverages the FAN4855MTCX's accurate feedback loop and stable regulation - though dedicated LED drivers may offer higher efficiency for large arrays.
FAN4855MTCX Specifications
- Product attributes
- Attribute value
- Manufacturer:
- onsemi
- Series:
- -
- Package/Case:
- 8-TSSOP (0.173", 4.40mm Width)
- Packaging:
- Tape & Reel (TR)
- 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
FAN4855MTCX FAQ
1.How can I place an order for FAN4855MTCX through Aetrix?
Please submit a Request for Quotation (RFQ) for FAN4855MTCX 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 FAN4855MTCX reliable?
The price and inventory of FAN4855MTCX are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for FAN4855MTCX is usually 5 days.
3.What payment methods are accepted for FAN4855MTCX?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for FAN4855MTCX transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for FAN4855MTCX?
FAN4855MTCX orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your FAN4855MTCX 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 FAN4855MTCX?
For technical support, including FAN4855MTCX datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your FAN4855MTCX requirements.
6.How does Aetrix verify that FAN4855MTCX is sourced from the original manufacturer or authorized distributors?
All FAN4855MTCX 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 FAN4855MTCX meets industry standards.
7.What is the process for return or replacement of FAN4855MTCX?
All FAN4855MTCX units undergo pre-shipment inspection (PSI). If there is an issue with FAN4855MTCX, 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 FAN4855MTCX part is unused and in its original packaging.
Return procedure for FAN4855MTCX:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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