FS6271规格书：推荐电感值3.3μH~4.7μH，需关注饱和电流与1MHz磁芯损耗

KKW117

1MHz, 2.5A Step-Up Current Mode PWM ConverterGeneral Description

The FS6271 is a current mode boost DC-DC converter. Its PWM circuitry with built-in 0.2Ω power MOSFET make this regulator highly power efficient. The internal compensation network also minimizes as much as 6 external component counts. The non-inverting input of error amplifier connects to a 0.6V precision reference voltage and internal soft-start function can reduce the inrush current.

The FS6271 is available in the SOT23-6L package and provides space-saving PCB for the

application fields.

Features

Ø Adjustable Output up to 12V

Ø Internal Fixed PWM frequency: 1.0MHz

Ø Precision Feedback Reference Voltage: 0.6V (±2%)

Ø Internal 0.2Ω, 2.5A, 16V Power MOSFET

Ø Shutdown Current: 0.1μA

Ø Over Temperature Protection

Ø Over Voltage Protection

Ø Adjustable Over Current Protection: 0.5A ~ 2.5A

Ø Package: SOT23-6L

Applications

Ø Chargers

Ø LCD Displays

Ø Digital Cameras

Ø Handheld Devices

Ø Portable Products

Typical Application Circuit

Function Block Diagram

Pin DescriptionsMarking Information

Lot Number: Wafer lot number’s last two digits

For Example: 132386TB à 86

Year: Production year’s last digit

Part Number Code: Part number identification code for this product. It should be always “AL”.Note1:

θJA is measured in the natural convection at TA=25°C on a low effective thermal conductivity test board of JEDEC 51-3 thermal measurement standard.

IR Re-flow Soldering CurveTypical Operating Characteristics (VCC=3.3V, VOUT=5V, TA= 25°C, unless otherwise noted)Function Description

Operation

The FS6271 is a current mode boost converter. The constant switching frequency is 1MHz and operates with pulse width modulation (PWM). Build-in 16V / 2.5A MOSFET provides a high output voltage. The control loop architecture is peak current mode control; therefore slope compensation circuit is added to the current signal to allow stable operation for duty cycles larger than 50%.

Soft Start Function

Soft start circuitry is integrated into FS6271 to avoid inrush current during power on. After the IC is enabled, the output of error amplifier is clamped by the internal soft-start function, which causes PWM pulse width increasing slowly and thus reducing input surge current.

Current Limit Program

A resistor between OC and GND pin programs peak switch current. The resistor value should be between 19k and 96k. The current limit will be set from 2.5A to 0.5A. Keep traces at this pin asshort as possible. Do not put capacitance at this pin. To set the over current trip point accordingto the following equation:

Over Temperature Protection (OTP)

FS6271 will turn off the power MOSFET automatically when the internal junction temperature is over 150°C. The power MOSFET wake up when the junction temperature drops 30°C under the OTP threshold temperature.

Over Voltage Protection (OVP)

In some condition, the resistive divider may be unconnected, which will cause PWM signal to operate with maximum duty cycle and output voltage is boosted higher and higher. The power MOSFET will be turned off immediately, when the output voltage exceeds the OVP threshold level. The FS6271’s OVP threshold is 16V.

Application Information

Inductor Selection

Inductance value is decided based on different condition. 3.3uH to 4.7µH inductor value is recommended for general application circuit. There are three important inductor specifications, DC resistance, saturation current and core loss. Low DC resistance has better power efficiency. Also, it avoid inductor saturation which will cause circuit system unstable and lower core loss at 1MHz.

Capacitor Selection

The output capacitor is required to maintain the DC voltage. Low ESR capacitors are preferred to reduce the output voltage ripple. Ceramic capacitor of X5R and X7R are recommended, which have low equivalent series resistance (ESR) and wider operation temperature range.

Diode Selection

Schottky diodes with fast recovery times and low forward voltages are recommended. Ensure the diode average and peak current rating exceed the average output current and peak inductor current. In addition, the diode’s reverse breakdown voltage must exceed the output voltage.

Output Voltage Programming

The output voltage is set by a resistive voltage divider from the output voltage to FB. The output voltage is:

Layout Considerations

1. The power traces, consisting of the GND trace, the LX trace and the VCC trace should be kept short, direct and wide.

2. LX、L and D switching node, wide and short trace to reduce EMI.

3. Place CIN near VCC pin as closely as possible to maintain input voltage steady and filter out the

pulsing input current.

4. The resistive divider R1and R2 must be connected to FB pin directly as closely as possible.

5. FB is a sensitive node. Please keep it away from switching node, LX.

6. The GND of the IC, CIN and COUT should be connected close together directly to a ground plane.

Typical Application

Note: Don’t pull the Vout back to the FS6271’s Vcc pin. When the system receives the noise, it will lead to Vout ripple too high and over the absolute maximum rating of the Vcc pin.

Package Outline

Note:

1. Package dimensions are in compliance with JEDEC outline: MO-178 AB.

2. Dimension “D” does not include molding flash, protrusions or gate burrs.

3. Dimension “E1” does not include inter-lead flash or protrusions.

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