HT3402S

4/11

40V/2A Constant Voltage & Constant Current Buck Converter IC

www.hotchip.com.cn

Ver1.1

Over Current Protection



HT3402S has an internal over-current protection circuit that limits the inrush current during start-up. At

the beginning of the start-up, the over-current protection circuit will detect the current, if it’s too high to

exceed the safe value, the PMOS will be turn-off. But when output is rise to the design voltage, the

protect function will not active anymore. The I-EA will replace the function to limiting the current.

Application Information



The basic application circuit of HT3402S is shown in Figure 1. External components selection is

depend on load requirement, and begin with the selection of inductor followed by capacitor

Inductor Selection



For most application, HT3402S operates well with inductors of 100uH, the inductor is selected to limit

the ripple current with some predetermined value, typically 20～40% of the full load current at the

maximum input voltage. The equation of

inductance is as below: below:



The DC current rating of the inductor should be at least equal to the maximum load current plus half of

the ripple current to prevent core saturation. For example△IL=1000mA×40%=400mA, thus, a 1400mA

rated inductor should be enough for most application(1000mA+400mA). For better efficiency, choose a

low DCR inductor.

Input Capacitor Selection



The input capacitor reduces surge current drawn from input and switching noise from the device. Input

capacitor impedance at the switching frequency shall be less than input s ource impedance to prevent

high frequency switching current passing to the input. A low ESR i nput capacitor sized for max. RMS

current must be used. A 100uF ceramic capacitor for most application is sufficient and recommended.

Output Capacitor Selection



The output capacitor is required to keep the output voltage ripple small and to stabilize regulation loop .

It must have low impedance at the switching frequency. Ceramic capacitors with X5R or X7R dielectrics

by below equation: