LTC3735
28
3735fa
TYPICAL APPLICATION
Figure 14 shows a typical application using the LTC3735
to power the mobile CPU core. The input can vary from
5V to 24V; the output voltage can be programmed from
0.7V to 1.708V with a maximum current of 32A. By only
modifying the external MOSFET and inductor selection,
higher load current capability (up to 40A) can be achieved.
The power supply in Figure 14 receives a VRON signal for
ON/OFF control. After soft-start, the output voltage is set
at 1.2V until the assertion of the MCH_PG signal. After
about a 50µs delay, the VID5-VID0 bits gain the control
over the output voltage and program it between 0.7V and
1.708V. When the STP_CPUB signal is low, a deep sleep
state is indicated and the output voltage is decreased by
about 1.04%. When the DPRSLPVR signal is high, a deeper
sleep state is indicated and the output voltage becomes
0.748V regardless of the states of the VID bits. Active
voltage positioning is accomplished with a resistor from
the I
TH
to the V
OA
+
pin. Lower resistance yields a steeper
AVP slope while higher resistance provides a flatter slope.
Finally, the PGOOD output is masked for 110µs during VID
change or state transition.
MCH_PG
DPRSLPVR
STP_CPUB
PSIB
FREQSET
VID0
VID1
VID2
VID3
VID4
VID5
PGOOD
I
TH
RUN/SS
SGND
V
FB
PV
CC
BOOST1
BOOST2
TG1
SW1
BG1
PGND
SENSE1
+
SENSE1
–
TG2
SW2
BG2
SENSE2
+
SENSE2
–
RBOOT
RDPRSLP
RDPSLP
V
OA
+
OAOUT
V
OA
–
V
CCP
_PG/MCH_PG
DPRSLPVR
STP_CPUB
PSIB
VID0
VID1
VID2
VID3
VID4
VID5
36
2
8
4
3
19
20
21
22
23
24
35
17
16
9
1
28
34
31
33
32
27
26
10
11
30
29
25
12
13
18
14
15
5
7
6
PGOOD
2k
3.3V
BAT54
1M
3.3k
232k
47pF
0.1µF
0.1µF
SW2
SW1
470pF
100pF
1µF
X5R
5V
4.7µF
X5R
V
OUT
LTC3735
0.002Ω
0.002Ω
1µF
Q1
Q2
Q3
Q4
1nF
D1
D2
L1
0.8µH
L2
0.8µH
1µF
C5: PANSONIC SP CAPS EEFSX0D181R
OR SANYO POSCAP 2R5TPE220M9
D1, D2: B340A
L1, L2: CDEP 104-OR8MC-L
Q1, Q3: IRF7811W OR Si7860DP
Q2, Q4: IRF7811W ¥2 OR Si7856DP
10Ω10Ω
10Ω
13.3k12.7k
1.27M
1M 1%
56.2k
13.3k
549k
3735 F14
10Ω
1nF
C1
10µF ×4
35V X5R
V
IN
5V ~ 24V
V
OUT
0.7V ~ 1.708V
AT 32A
C5
×3
2.2µF
+
V
OA
+
470pF
1000pF
V
RON
100k
5V
Si1034X
V
OA
+
PSIB
249k
80.6k
1M
MMBT3904 MMBT3904
2N7002
1µF
V
RON
BAT54C
3.3V 3.3V 3.3V
2k
PGOOD
4.12k
43.2k
IMVP4_PG
1.9k
CLK_EN#
100Ω100Ω
S1
+
S2
+
S1
+
S2
+
Figure 14. 5V to 24V Input, 0.7V to 1.708V Output, 32A IMVP-IV Compatible Power Supply
