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LTC3633 Datasheet, PDF (22/28 Pages) Linear Technology – Dual Channel 3A, 15V Monolithic Synchronous Step-Down Regulator | |||
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LTC3633
APPLICATIONS INFORMATION
A 47μF ceramic capacitor should be sufï¬cient for channel
1. Solving the same equation for channel 2 (using 5% of
VOUT for VDROOP) results in 27μF of capacitance (22μF is
the closest standard value).
CIN should be sized for a maximum current rating of:
1.8V(13.2V â1.8V)
IRMS = 3A
13.2V
= 1A
Solving this equation for channel 2 results in an RMS
input current of 1.3A. Decoupling each VIN input with
a 47μF ceramic capacitor should be adequate for most
applications.
Lastly, the feedback resistors must be chosen. Picking R1
and R3 to be 12.1k, R2 and R4 are calculated to be:
R2
=
(12.1k)
â¢
1.8V
0.6V
â 1=
24.2k
R4
=
(12.1k)
â¢
3.3V
0.6V
â 1
=
54.5k
The ï¬nal circuit is shown in Figure 8.
VIN
12V
CIN
47μF
Ã2
R5
162k
VOUT2
3.3V AT 3A
COUT2
22μF
L2
1μH 0.1μF
R4
R3
54.9k 12.1k
RUN1
RUN2
VIN2 VIN1 INTVCC
ITH1
LTC3633
ITH2
V2P5
RT
TRACKSS2
PGOOD2
BOOST2
MODE/SYNC
PHMODE
TRACKSS1
PGOOD1
BOOST1
SW2
VON2
VFB2 SGND PGND
SW1
VON1
VFB1
C2
2.2μF
L1
0.1μF 0.68μH
R1
R2
12.1k 24.3k
Figure 8. Design Example Circuit
VOUT1
1.8V AT 3A
COUT1
47μF
3633 F08
3633f
22
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