http://www.belling.com.cn

- 4-

8/8/2006

BL8501

TYPICAL APPLICATION AND APPLICATION HINTS

Example: Output Voltage=3.3V

PMOS: SI9435

L: 27

H

SD1: 1N5817

C1: 10

F (Ceramic Type or Electrolytic Type)

C2: 0.1

F (Ceramic Type or Electrolytic Type)

C3: 47

F (Tantalum Type)

C4: 1000pF (Ceramic Type)

R1=10

, R2=14.3k

, R3=2.7k

, R4=33k

When you use this chip, consider the following issues:

As shown in the block diagram, a parasitic diode is formed in the terminal, this diode is not

formed for load current, therefore do not use it in such a way. When you control the CE pin

by another power supply, do not make its “H” level more than the voltage level of

IN

V

pin.

Set external components as close as possible to the IC and minimize the connection

between the components and the IC. In particular, a capacitor should be connected to

OUT

V

pin with the minimum connection. Make sufficient ground and reinforce supplying. A large

switching current could flow through the connection of power supply, an inductor and the

connection of

OUT

V

. If the impedance of the connection of power supply is high, the voltage

level of power supply of the IC fluctuates with the switching current. This may cause unstable

operation of the IC.

Protection circuit may work if the maximum duty cycle continues for the time defined in the

electrical characteristics. Once after stopping the output voltage, output will restart with

soft-start operation. If the difference between input voltage and output voltage is small, the

protection circuit may work.

Use capacitors with a capacity of 47

F or more for

OUT

V

pin, and with good high