AEROSEMI

MT3608
High Efficiency 1.2MHz
2A Step Up Converter

FEATURES GENERAL DESCRIPTION

• Integrated 80mΩ Power MOSFET The MT3608 is a constant frequency, 6-pin SOT23
• 2V to 24V Input Voltage current mode step-up converter intended for small,
• 1.2MHz Fixed Switching Frequency low power applications. The MT3608 switches at
• Internal 4A Switch Current Limit 1.2MHz and allows the use of tiny, low cost
• Adjustable Output Voltage capacitors and inductors 2mm or less in height.
• Internal Compensation Internal soft-start results in small inrush current and
• Up to 28V Output Voltage extends battery life.
• Automatic Pulse Frequency Modulation The MT3608 features automatic shifting to pulse
Mode at Light Loads frequency modulation mode at light loads. The
• up to 97% Efficiency MT3608 includes under-voltage lockout, current
• Available in a 6-Pin SOT23-6 Package 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
APPLICATIONS package.
• Battery-Powered Equipment
• Set-Top Boxed
• LCD Bais Supply
• DSL and Cable Modems and Routers
• Networking cards powered from PCI
or PCI express slots

TYPICAL APPLICATION
Efficiency
Efficiency (%)

Iout (mA)

Figure 1. Basic Application Circuit Figure 2. Efficiency Curve

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 MT3608
ABSOLUTE MAXIMUM RATINGS
IN, EN voltages ………..….…… -0.3V to 26V SW Voltage ……………………..-0.3V to 30V
Operating Temperature….... -40°C to +85°C Storage Temperature Range -65°C to 150°C
FB Voltages ................................-0.3V to 6V Peak SW Sink and Source Current ………4A
Junction Temperature ………………...160°C Lead Temperature (Soldering, 10s) ...+300°C

PACKAGE/ORDER INFORMATION
SW 1 6 NC

GND 2 5 IN

FB 3 4 EN

SOT23-6
SOT23-5
(MT3608)
(MT3540)

PIN DESCRIPTION

PIN NAME FUNCTION

Power Switch Output. SW is the drain of the internal MOSFET switch. Connect the
1 SW
power inductor and output rectifier to SW. SW can swing between GND and 28V.

2 GND Ground Pin

3 FB Feedback Input. The FB voltage is 0.6V. Connect a resistor divider to FB.

Regulator On/Off Control Input. A high input at EN turns on the converter, and a
4 EN low input turns it off. When not used, connect EN to the input supply for automatic
startup.
Input Supply Pin. Must be locally bypassed.
5 IN

6 NC NC

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 MT3608
ELECTRICAL CHARACTERISTICS

(VIN=VEN=5V, TA = 25°C, unless otherwise noted.)

Parameter Conditions MIN TYP MAX unit
Operating Input Voltage 2 24 V
Under Voltage Lockout 1.98 V
Under Voltage Lockout Hysteresis 100 mV
Current (Shutdown) VEN= 0V 0.1 1 µA
Quiescent Current (PFM) VFB=0.7V，No switch 100 200 µA
Quiescent Current (PWM) VFB=0.5V，switch 1.6 2.2 mA
Switching Frequency 1.2 MHz
Maximum Duty Cycle VFB = 0V 90 %
EN Input High Voltage 1.5 V
EN Input Low Voltage 0.4 V
FB Voltage 0.588 0.6 0.612 V
FB Input Bias Current VFB = 0.6V -50 -10 nA
SW On Resistance (1) 80 150 mΩ
SW Current Limit (1) VIN= 5V, Duty cycle=50% 4 A
SW Leakage VSW = 20V 1 μA
Thermal Shutdown 155 ℃

Note:
1) Guaranteed by design, not tested.

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 MT3608
OPERATION
The MT3608 uses a fixed frequency, peak current The output voltage of the error amplifier the power
mode boost regulator architecture to regulate MOSFET is turned off. The voltage at the output of
voltage at the feedback pin. The operation of the the error amplifier is an amplified version of the
MT3608 can be understood by referring to the block difference between the 0.6V bandgap reference
diagram of Figure 3. At the start of each oscillator voltage and the feedback voltage. In this way the
cycle the MOSFET is turned on through the control peak current level keeps the output in regulation. If
circuitry. To prevent sub-harmonic oscillations at the feedback voltage starts to drop, the output of the
duty cycles greater than 50 percent, a stabilizing error amplifier increases. These results in more
ramp is added to the output of the current sense current to flow through the power MOSFET, thus
amplifier and the result is fed into the negative input increasing the power delivered to the output. The
of the PWM comparator. When this voltage equals 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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 MT3608
TYPICAL OPERATING CHARACTERISTICS
Efficiency Curve Efficiency Curve

Current limit(A)
Efficiency

Iout (mA) Iout(mA)

line Regulation Load regualation

Vout(V)
Vout(V)

Vin (V) Iout (mA)

Freq VS Vin Efficiency VS Vin

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 MT3608
APPLICATION INFORMATION

Setting the Output Voltage Layout Consideration

The internal reference VREF is 0.6V (Typical).The For best performance of the MT3608, the following
output voltage is divided by a resistor divider,R1 and guidelines must be strictly followed.
R2 to the FB pin. The output voltage is given by  Input and Output capacitors should be placed
R1 close to the IC and connected to ground plane
VOUT = VREF × (1 + ) to reduce noise coupling.
R2
 The GND should be connected to a strong
ground plane for heat sinking and noise
Inductor Selection protection.
The recommended values of inductor are 4.7 to  Keep the main current traces as possible as
22μH. Small size and better efficiency are the major short and wide.
concerns for portable device, such as MT3608 used  SW node of DC-DC converter is with high
for mobile phone. The inductor should have low core frequency voltage swing. It should be kept at a
loss at 1.2MHz and low DCR for better efficiency. To small area.
avoid inductor saturation current rating should be  Place the feedback components as close as
considered. possible to the IC and keep away from the
noisy devices.

Capacitor Selection
Input and output ceramic capacitors of 22μF are
recommended for MT3608 applications. For better
voltage filtering, ceramic capacitors with low ESR
are recommended. X5R and X7R types are suitable
because of their wider voltage and temperature
ranges.

Diode Selection
Schottky diode is a good choice for MT3608
because of its low forward voltage drop and fast
reverses recovery. Using Schottky diode can get
better efficiency. The high speed rectification is also
a good characteristic of Schottky diode for high
switching frequency. Current rating of the diode must
meet the root mean square of the peak current and
output average current multiplication as following :
I D ( RMS ) ≈ I OUT × I PEAK

The diode’ s reverse breakdown voltage should be

larger than the output voltage.

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 MT3608
PACKAGE DESCRIPTION

TOP VIEW RECOMMENDED LAND PATTERN

FRONT VIEW SIDE VIEW

DETAIL “A”

Figure 4. TSOT23-6/SOT23-6 Physical Dimensions

NOTE:
1)ALL DIMENSIONS ARE IN MILLIMETERS.
2) PACKAGE LENGTH DOES NOT INCLUDE MOLD FLASH,PROTRUSION OR GATE BURR.
3) PACKAGE WIDTH DOES NOT INCLUDE INTERLEAD FLASH OR PROTRUSION.
4) LEAD COPLANARITY (BOTTOM OF LEADS AFTER FORMING) SHALL BE 0.10 MILLIMETERS MAX.
5) DRAWING CONFORMS TO JEDEC MO-193, VARIATION AB.
6) DRAWING IS NOT TO SCALE.
7) PIN 1 IS LOWER LEFT PIN WHEN READING TOP MARK FROM LEFT TO RIGHT, (SEE EXAMPLE TOP MARK)

MT3608/V1.0

Xi' an Aerosemi Technology Co., Ltd

T e l : 029-88868021 0755-82879616 021-51905952 7
Fax: 029-88445284 0755-82877171 021-51905952
Http://www.aerosemi.com
E-mail: sales@aerosemi.com
Aerosemi Technology Co., Ltd