Datasheet

LTC3441
12
3441fa
APPLICATIO S I FOR ATIO
WUUU
The unity-gain frequency of the error amplifier with the
Type I compensation is given by:
f
RCP
Hz
UG
=
π
1
211•• •
Most applications demand an improved transient response
to allow a smaller output filter capacitor. To achieve a
higher bandwidth, Type III compensation is required. Two
zeros are required to compensate for the double-pole
response.
f
eRC
Hz
Which is extremely close to DC
f
RC
Hz
f
RC
Hz
f
RC
Hz
POLE
P
ZERO
ZP
ZERO
Z
POLE
ZP
1
3
1
1
1
2
1
2
2
1
232 1
1
2
1
21
1
2
≈
π
=
π
=
π
=
π
•• • •
•• •
•• •
•• •
Figure 7. Error Amplifier with Type I Compensation
Figure 8. Error Amplifier with Type III Compensation
1.22V
R1
R2
3441 F07
FB
12
V
C
C
P1
V
OUT
11
–
+
ERROR
AMP
1.22V
R1
R2
3441 F08
FB
12
V
C
C
P1
C
Z1
R
Z
V
OUT
11
C
P2
–
+
ERROR
AMP
SW1
PV
IN
V
IN
SHDN/SS
MODE/SYNC
PGND
5
8
12
11
2
6
4
9
10
1
7
3
SW2
V
OUT
FB
V
C
GND
PGND
LTC3441
C1
10μF
*1 = Burst Mode OPERATION
0 = FIXED FREQUENCY
C1: TAIYO YUDEN JMK212BJ106MG
C2: TAIYO YUDEN JMK325BJ476MM
L1: TOKO A916CY-4R7M
2.5V TO 4.2V
Li-Ion
*
R3 15k
5M
R1
348k
2.2k
C2
47μF
V
OUT
3.3V
1A
R2
200k
C4 220pF
220pF
3441 F09
L1
4.7μH
Load Transient Response,
100mA to 1A
V
OUT
100mV/DIV
1A
100mA
100μs/DIV 3441 G01
Figure 9. Fast Transient Response Compensation for Step Load or Mode Change