Datasheet

LTC3868-1
30
38681fd
TYPICAL APPLICATIONS
Start-Up SW Node Waveforms
Figure 12. High Effi ciency Dual 8.5V/3.3V Step-Down Converter
SENSE1
+
SENSE1
–
SENSE2
–
SENSE2
+
V
FB1
I
TH1
SGND
EXTV
CC
RUN1
RUN2
FREQ
SS2
V
FB2
SS1
PLLIN/MODE
PGOOD1
BG1
SW1
BOOST1
TG1
V
IN
INTV
CC
PGND
TG2
BG2
BOOST2
SW2
C1
1nF
R
B1
215k
C
OUT1
, C
OUT2
: SANYO 10TPD150M
L1: SUMIDA CDEP105-3R2M
L2: SUMIDA CDEP105-7R2M
MTOP1, MTOP2, MBOT1, MBOT2: VISHAY Si7848DP
C
F1
15pF
C
ITH1A
150pF
C
SS1
0.1µF
C
SS2
0.1µF
C
ITH1
820pF
C
INT
4.7µF
C
B1
0.47µF
C
B2
0.47µF
D1
V
IN
9V TO 24V
D2
LTC3868-1
L1
3.3µH
L2
7.2µH
R
SENSE1
7m
R
SENSE2
10m
MBOT1
MTOP2
MTOP1
MBOT2
38681 F12
100k
INTV
CC
C
OUT1
150µF
V
OUT1
3.3V
5A
V
OUT2
8.5V
3A
C
IN
22µF
C
OUT2
150µF
R
A1
68.1k
R
A2
44.2k
R
B2
442k
C
F2
39pF
R
ITH1
15k
C2
1nF
I
TH2
C
ITH2
680pF
C
ITH2A
100pF
R
ITH2
27k
Effi ciency vs Output Current
OUTPUT CURRENT (A)
0.00001 0.0001
40
EFFICIENCY (%)
50
60
70
80
0.001 0.01 0.1 1 10
38681 F12b
30
20
10
0
90
100
V
IN
= 12V
Burst Mode OPERATION
V
OUT
= 8.5V V
OUT
= 3.3V
38681 F12c
V
OUT2
2V/DIV
V
OUT1
2V/DIV
20ms/DIV
38681 F12d
SW1
5V/DIV
SW2
5V/DIV
1µs/DIV