优秀DCDC升压

MT3608

2A Step Up Converter

FEATURES

Integrated 80mΩ Power MOSFET 2V to 24V Input Voltage

1.2MHz Fixed Switching Frequency Internal 4A Switch Current Limit Adjustable Output Voltage Internal Compensation Up to 28V Output Voltage

Automatic Pulse Frequency Modulation Mode at Light Loads up to 97% Efficiency

Available in a 6-Pin SOT23-6 Package

GENERAL DESCRIPTION

APPLICATIONS

Battery-Powered Equipment Set-Top Boxed LCD Bais Supply

DSL and Cable Modems and Routers Networking cards powered from PCI or PCI express slots

The MT3608 is a constant frequency, 6-pin SOT23 current mode step-up converter intended for small, low power applications. The MT3608 switches at 1.2MHz and allows the use of tiny, low cost capacitors and inductors 2mm or less in height. Internal soft-start results in small inrush current and extends battery life.

The MT3608 features automatic shifting to pulse frequency modulation mode at light loads. The MT3608 includes under-voltage lockout, current limiting, and thermal overload protection to prevent damage in the event of an output overload. The MT3608 is available in a small 6-pin SOT-23 package.

TYPICAL APPLICATION

Efficiency

Efficiency (%)

Iout (mA)

Figure 2. Efficiency Curve

MT3608

ABSOLUTE MAXIMUM RATINGS

IN, EN voltages ………..….…… -0.3V to 26V Operating Temperature….... -40°C to +85°C FB Voltages ................................-0.3V to 6V Junction Temperature ………………...160°C SW Voltage ……………………..-0.3V to 30V Storage Temperature Range -65°C to 150°C Peak SW Sink and Source Current ………4A Lead Temperature (Soldering, 10s) ...+300°C

PACKAGE/ORDER INFORMATION

NC

IN

EN

PIN DESCRIPTION

MT3608

ELECTRICAL CHARACTERISTICS

Note:

1) Guaranteed by design, not tested.

MT3608

OPERATION

The MT3608 uses a fixed frequency, peak current mode boost regulator architecture to regulate voltage at the feedback pin. The operation of the MT3608 can be understood by referring to the block diagram of Figure 3. At the start of each oscillator cycle the MOSFET is turned on through the control circuitry. To prevent sub-harmonic oscillations at duty cycles greater than 50 percent, a stabilizing ramp is added to the output of the current sense amplifier and the result is fed into the negative input of the PWM comparator. When this voltage equals

The output voltage of the error amplifier the power MOSFET is turned off. The voltage at the output of the error amplifier is an amplified version of the difference between the 0.6V bandgap reference voltage and the feedback voltage. In this way the peak current level keeps the output in regulation. If the feedback voltage starts to drop, the output of the error amplifier increases. These results in more current to flow through the power MOSFET, thus increasing the power delivered to the output. The MT3608 has internal soft start to limit the amount of input current at startup and to also limit the amount of overshoot on the output.

Figure 3. Functional Block Diagram

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