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MA5604

Major Power Technology Co., Ltd.

Rev.1.3

Apr.12, 2017



FUNCTION DESCRIPTIONS

The MA5604 is a synchronous rectified, current-mode, step-down regulator. It regulates

of load current.

The MA5604 uses current-mode control to regulate the output voltage. The output voltage

is measured at FB through a resistive voltage divider and amplified through the internal Tran

conductance error amplifier. The voltage at the COMP pin is compared to the switch current

measured internally to control the output voltage.

The converter uses internal N-Channel MOSFET switches to step-down the input voltage

to the regulated output voltage. Since the high side MOSFET requires a gate voltage greater

than the input voltage, a boost capacitor connected between SW and BS is needed to drive the

high side gate. The boost capacitor is charged from the internal 5V rail when SW is low.

voltage comparator is tripped and the COMP pin is discharged to GND, forcing the high-side

switch off.



APPLICATION INFORMATION

COMPONENT SELECTION

Setting the Output Voltage

The output voltage is set using a resistive voltage divider from the output voltage to FB

pin. The voltage divider divides the output voltage down to the feedback voltage by the ratio.

Thus the output voltage is:

2

2

1

R

R

R 

Ω, and R1 is 40kΩ.

Inductor Selection

The inductor is required to supply constant current to the output load while being driven

by the switched input voltage. A larger value inductor will result in less ripple current that will

result in lower output ripple voltage. However, the larger value inductor will have a larger

physical size, higher series resistance, and/or lower saturation current. A good rule for

determining the inductance to use is to allow the peak-to-peak ripple current in the inductor to

be approximately 30% of the maximum switch current limit.

VIN

<28V

<35V

Inductor

47uH

33uH

The choice of which style inductor to use mainly depends on the price vs. size

requirements and any EMI requirements.