Figure 4

Charging Status Indication

Where,

HM4033 DRV is HM4033’s DRV pin, VIN is the charger’s input voltage. LED1 is for charging status

indication, LED2 is for termination indication. R1 and R2 are the LED current limit resistors.

Design Procedure

The following procedure should be followed to design

HM4033’s application circuit:

（

1）Decide charge current based on the battery capacity and charge time

（

2）Estimate average inductor current based on input voltage, battery voltage and charge current

（

（

4）Determine the inductor value based on the switching frequency

（

5）Design resistor divider formed by R1 and R2 for battery voltage feedback

（

6）Calculate capacitance of C3

PCB Considerations

Careful PCB layout is critical to achieve low switching losses and stable operation.



Use a multilayer board whenever possible for better noise immunity.



The negative terminals of input bypass capacitor and output capacitor should be as close as possible to the

source of N-channel MOSFET



The analog ground should be separated with power ground plane.



To ensure low EMI, the copper plane for diode, N-channel MOSFET, inductor, input capacitor and output

capacitor should be as small as possible,



HM4033