LTC3868-1 Datasheet, PDF (30/38 Pages) Linear Technology – Low IQ, Dual 2-Phase Synchronous Step-Down Controller

LTC3868-1
Typical ApplicationS
R_B1
215k
C_F1
15pF C1
R_A1
1nF
68.1k
C_ITH1A 150pF
R_ITH1 15k
C_ITH1 820pF _{CSS1 0.1µF}
C_SS2 0.1µF
C_ITH2 680pF _{RITH2 27k}
LTC3868-1
SENSE1⁺
SENSE1^–
V_FB1
I_TH1
PGOOD1
BG1
SW1
BOOST1
TG1
V_IN
SS1
INTV_CC
PLLIN/MODE
SGND
EXTV_CC
RUN1
RUN2
FREQ
PGND
TG2
BOOST2
SS2
SW2
I_TH2
BG2
INTV_CC
100k
C_B1
0.47µF
D1
C_INT
4.7µF
D2
C_B2
0.47µF
R_A2
44.2k
C_ITH2A 100pF
C2
C_{F2 1nF}
39pF
V_FB2
SENSE2^–
SENSE2⁺
R_B2
442k
C_OUT1, C_OUT2: SANYO 10TPD150M
L1: SUMIDA CDEP105-3R2M
L2: SUMIDA CDEP105-7R2M
MTOP1, MTOP2, MBOT1, MBOT2: VISHAY Si7848DP
MBOT1
L1
3.3µH
MTOP1
R_SENSE1
7mΩ
V_IN
C_IN ^{9V TO 24V}
22µF
C_OUT1
150µF
V_OUT1
3.3V
5A
MTOP2
L2
R_SENSE2
7.2µH 10mΩ
MBOT2
V_OUT2
8.5V
C_OUT2 3A
150µF
38681 F12
Efficiency vs Output Current
100
90
80
V_OUT = 8.5V
70
V_OUT = 3.3V
60
50
40
30
20
10
0
0.00001 0.0001 0.001
V_IN = 12V
Burst Mode OPERATION
0.01 0.1 1 10
OUTPUT CURRENT (A)
38681 F12b
Start-Up
20ms/DIV
V_OUT2
2V/DIV
V_OUT1
2V/DIV
SW1
5V/DIV
SW2
5V/DIV
38681 F12c
Figure 12. High Efficiency Dual 8.5V/3.3V Step-Down Converter
30
SW Node Waveforms
1µs/DIV
38681 F12d
38681fb