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
V
IN
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
V
OUT
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
V
OUT
. 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
http://www.belling.com.cn
F or more for
V
OUT
pin, and with good high
8/8/2006
- 4-
Total
10
Pages
BELLING [ SHANGHAI BELLING CO., LTD. ]
