Datasheet

DocID14117 Rev 4 21/44
B5973D Closing the loop
44
In summary, the open loop gain can be expressed as:
Equation 15
Example:
Considering R
C
= 2.7 k, C
C
= 22 nF and C
P
= 220 pF, the poles and zeroes of A
0
are:
F
P1
= 9 Hz
F
P2
= 256 kHz
F
Z1
= 2.68 kHz
If L = 22 µH, C
OUT
= 100 µF and ESR = 80 m, the poles and zeroes of A
LC
become:
F
PLC
= 3.39 kHz
F
0
= 19.89 kHz
Finally R
1
= 5.6 k and R
2
= 3.3 k.
The gain and phase bode diagrams are plotted respectively in Figure 11 and Figure 12.
Figure 11. Module plot
Gs G
PWM
s
R
2
R
1
R
2
+
-------------------- A
O
s A
LC
 s=