Datasheet

R2
R1 R2
0.242
+
=
3.3 V
R1 R2
50 A
66 k+ =
m
= W
REF
OUT
V
0.8 V
V 3.3 V
0.242b = = =
P2
1 1
f
2 R3 C2 2 30 k 27 pF
196 kHz=
p ´ ´ p ´ W ´
= =
Z1
1 1
f 4.8 kHz
2 R3 C1 2 30 k 1.1 nF
= = =
p ´ ´ p ´ W ´
BUCK CFB
REF
C
OUTB OUTB
Gm R3 K
V
f
2 C V
1mS 30 k 4.16 S 0.8 V
48 kHz
2 100 μF 3.3 V
´ ´
=
p ´
´ W ´ ´
= =
p ´ ´
´
SW
C1
C2
2 R3 C1
1.1nF
27 pF
2 30 k 1.1nF
f
1
2
400 kHz
1
2
=
p ´ ´ ´
= =
p ´ W ´ ´
æ ö
-
ç ÷
è ø
æ ö
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TPS43330-Q1
TPS43332-Q1
SLVSA82E –MARCH 2011–REVISED APRIL 2013 www.ti.com
f
C
is close to the target bandwidth of 50 kHz.
The resulting zero frequency f
Z1
f
Z1
is close to the f
C
guideline of 5 kHz.
The second pole frequency f
P2
f
P2
is close to the f
SW
/ 2 guideline of 200 kHz.
Hence, the design satisfies all requirements for a good loop.
Resistor Divider Selection for Setting V
OUT
Voltage
Choose the divider current through R1 and R2 to be 50 µA. Then
and
Therefore, R2 = 16 kΩ and R1 = 50 kΩ.
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