Micrel MIC45208, Manual, Page: 4 / 9

Micrel, Inc. MIC45208 Evaluation Board
August 19, 2015 4 Revision 2.0
Setting the Switching Frequency
The MIC45208 switching frequency can be adjusted by
changing the value of resistors R1 and R2. The switching
frequency also depends on V
IN
, V
OUT
, and load conditions.
Figure 2. Switching Frequency Adjustment
Equation 5 illustrates the estimated switching frequency:
2 R 1 R
2 R
f f
O SW
+
× =
Eq. 5
Where f
O
= 600kHz
R1 = 100k
Ω (recommended)
R2 is selected to set the required switching frequency as
shown in
Figure 3 :
Figure 3. Switching Frequency vs. R2
0
100
200
300
400
500
600
700
800
10.00 100.00 1000.00 10000.00
S
W
F
RE
Q
(
k
Hz
)
R2 (k
Ω)
Switching Frequency
V
OUT
= 5V
V
IN
= 12V
R1 = 100k
Ω