MT3608 Step Up Adjustable Voltage Regulator Module

Table of Contents

MT3608 Step Up Adjustable Voltage Regulator Module, The MT3608 is a constant frequency, 6-pin SOT23 current mode step-up converter intended for small, low-power applications. The MT3608 switches at1. 2MHz and allows the use of tiny, low-cost capacitors and inductors 2 mm 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.

It is a DC-DC step up adjustable boost converter. It can take input voltages as low as 2V and step up the output to as high as 28V. The MT3608 features automatic shifting to pulse frequency modulation mode at light loads. It includes under-voltage lockout, current limiting, and thermal overload protection.

This module has a multiturn trimpot (potentiometer) that you can use to adjust the output voltage. Since the trimpot has 25 turns of adjustment, you can easily adjust the output of the module to exactly the voltage you need.

Boost converters are a great way to easily increase a given voltage, but that boost comes at the cost of less output current compared to input current. Since this is a boost converter, the output voltage has to be higher than the supplied input voltage.

Schematic MT3608 Step Up Adjustable Voltage Regulator Module

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

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 uses a fixed frequency, peak current mode boost regulator architecture to regulate voltage at the feedback pin. The operation of the MT3608. 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 of 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 flowing 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.

Setting the Output Voltage
The internal reference VREF is 0.6V (Typical). The output voltage is divided by a resistor divider,R1 and R2, to the FB pin. The output voltage is given by:

Bom MT3608 Step Up Adjustable Voltage Regulator Module

Name	Designator	Footprint	Quantity
Resistors 1/4W
2.2KΩ (222)	R1	0805	1
100KΩ (104)	R2	3296P – Multiturn trimpot	1
Capacitors
22uF	C1,C2	1206	2
Semiconductors
SS34	D1	SMA(DO-214AC)	1
MT3608	U1	SOT-23-6 – IC	1
Miscellaneous
Header-Male-2.54_1x1	IN+,IN-,OUT+,OUT-	HDR-1×1/2.54	4
22uH	L1	7×7×4 – inductor	1
USB1	Micro USB	Connector	1