APPLICATION INFORMATION

Loop Operation

The HM6350 is a wide input range, high-efficiency, DC/DC step up switching regulator, integrated with a 120mΩ Low Side

Main MOSFET and 150mΩ synchronous MOSFET. It uses a PWM current-mode control scheme. An error amplifier integrates

error between the FB signal and the internal reference voltage. The output of the integrator is then compared to the sum of

a current-sense signal and the slope compensation ramp. This operation generates a PWM signal that modulates the duty

cycle of the power MOSFETs to achieve regulation for output voltage.

The peak current of the NMOS switch is also sensed to limit the maximum current flowing through the switch and the

inductor. The typical peak current limit is set to 2.8A. An internal temperature sensor prevents the device from getting

overheated in case of excessive power dissipation.

Light Load Operation

Traditionally, a fixed constant frequency PWM DC/DC regulator always switches even when the output load is small. When

energy is shuffling back and forth through the power MOSFETs, power is lost due to the finite RDSONs of the MOSFETs and

parasitic capacitances. At light load, this loss is prominent and efficiency is therefore very low. HM6350 employs a proprietary

control scheme that improves efficiency in this situation by enabling the device into a power saving mode during light load,

thereby extending the range of high efficiency operation.

Short-Circuit Protection

Unlike most step-up converters, the HM6350 allows for short circuits on the output. In the event of a short circuit, the device

a linear charge period with the current limited same as with the start-up period. In addition, the thermal shutdown circuits

disable switching if the die temperature rises above 150°C.

The HM6350 will continue to supply the output voltage even when the input voltage exceeds the output voltage. Since the

PMOS no longer acts as a low-impedance switch in this mode, power dissipation increases within the IC to cause a sharp

drop in efficiency. Limit the maximum output current to maintain an acceptable junction temperature.

PCB GUIDELINES

A recommended PCB layout is shown on the right hand.

Please place the output capacitors (COUT1 and COUT2)

just besides the chip. And wire GND out underneath the

IC body. And thus, the performance of HM6350 is

guaranteed, and a very compact PCB design is also

achieved

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