LTC3442 View Datasheet(PDF) - Linear Technology
Part Name
Description
MFG CO.
LTC3442
Linear Technology
'LTC3442' PDF : 20 Pages View PDF
LTC3442
APPLICATIONS INFORMATION
A simple Type I compensation network can be incorporated
to stabilize the loop, but at a cost of reduced bandwidth
and slower transient response. To ensure proper phase
margin using Type I compensation, the loop must be
crossed over a decade before the LC double pole. The
unity-gain frequency of the error amplifier with the Type I
compensation is given by:
fUG
=
2
•
π
•
1
R1•
CP1
Hz
referring to Figure 7.
Most applications demand an improved transient response
to allow a smaller output filter capacitor. To achieve a higher
bandwidth, Type III compensation is required, providing
two zeros to compensate for the double-pole response of
ERROR
AMP
1.22V
FB
12
VC
CP1
11
VOUT
R1
R2
3442 F07
Figure 7. Error Amplifier with Type I Compensation
the output filter. Referring to Figure 8, the location of the
poles and zeros are given by:
fPOLE1
≅
2
•
π
•
1
32e3
•
R1•
Hz
CP1
(which is extremely close to DC)
fZERO1
=
2•π
1
• RZ
Hz
• CP1
fZERO2
=
2
•
π
1
• R1•
Hz
CZ1
fPOLE2
=
2•π
1
• RZ
• CP2
Hz
where resistance is in ohms and capacitance is in Farads.
VOUT
ERROR
AMP
1.22V
FB
12
R1
CZ1
VC
RZ CP1
R2
11
CP2
3442 F08
Figure 9. Error Amplifier with Type III Compensation
TYPICAL APPLICATIONS
1MHz Li-Ion to 3.3V at 1.2A Converter with
Manual Mode Control (and Peak Current Limit Only)
L1
3.3µH
2.5V TO 4.2V
CIN
10µF
+
Li-Ion
1M
0.01µF
43.2k
SW1
SW2
LTC3442
VIN
VOUT
SHDN/SS
FB
RLIM
RT
SGND
VC
BURST
PGND
15k
470pF
340k 2.2k
220pF
200k
VOUT
3.3V
1.2A
COUT
22µF
BURST FIXED FREQ
CIN: TAIYO YUDEN JMK212BJ106MG
COUT: TAIYO YUDEN JMK325BJ226MM
L1: TDK RLF7030T-3R3M4R
3442 TA02
For more information www.linear.com/LTC3442
3442fb
15
Share Link: 