HT3402S

8/11

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

www.hotchip.com.cn

Ver1.1

Cable compensation vs Load Current

Quiescent current vs Input Voltage

Load Current[mA]

Input Voltage[V]

Layout Notice



C3 is adopted for filtering high Freq. noise, should be set as close as it can be to Pin #1 of U1, <1mm is

recommended; C1 is however with consideration of its size to be installed a bit distant. Input power flows

thru. C1 and then C3 to U1.



D1 generates higher heat and composes a loop with L1 and C2, it is suggested to arrange these three

components as close as possible, and keep distant from U1 with at least 10mm to avoid heat to trigger OTP

function on U1



Sensing Resistor connects to Pin # 3 and # 4 of U1, and routing must compose Kelvin Method between

anode of C1 and USB output so that sample being sensed is directly from both sides of Rsen, and avoid

from other resistance coming from other PCB route.

Current must flow from L1 to anode of C2, and connect to one node of Rsen, then flown out from the other

node to USB directly. If current flows inappropriately, sampling/ sensing resistance might increase and result

in lower output current.



Pin # 1/ 5/ 6/ 7/ 8 of U1 on PCB is recommended to manipulated with larger area of bare copper and a bit

thicker tin paste spread on this area can also help for better heat dissipation. This action can also apply to

both soldering pads of D1.



USB port on PCB can be managed on D+/ D- anodes with designated resistors if necessary to fit in with

Apple handsets, while in most occasions, put them short- CKT will also do.