LTC3720_15 Datasheet, PDF (21/24 Pages) Linear Technology – Single Phase VRM8.5 Current Mode Step-Down Controller

LTC3720
APPLICATIO S I FOR ATIO
The modified circuit is shown in Figure 8. Figures 9 and 10
show the transient response without and with active
voltage positioning. Both circuits easily stay within ±100mV
of the 1.5V output. However, the circuit with active voltage
positioning accomplishes this with only three output ca-
pacitors rather than five. Refer to Linear Technology
Design Solutions 10 for additional information about
active voltage positioning.
INT V_CC
INT V_CC
100k
C_SS
0.1pF
POWER GOOD
1
RUN/SS
28
BOOST
2
V_ON
27
TG
R_RNG1 R_RNG2
4.99k 45.3k
R_VP2
40.2k
3
PGOOD
4
V_RNG
5
FCB
26
SW
25
SENSE⁺
24
SENSE^–
R_VP1 12.4k
C_C 180pF
6
I_TH
23
PGND
7
LTC3720
22
SGND
BG
C_ION
0.01µF
330k
V_IN
C_FB
100pF
8
I_ON
9
V_FB
10
SGND
11
V_FB
12
V_OSENSE
21
INTV_CC
20
V_IN
19
EXTV_CC
18
V_CC
17
VID4
13
VID0
16
VID3
14
VID1
15
VID2
R_F
1Ω
C_B 0.33µF
V_IN
5V TO 24V
C_IN
10µF
35V
×3
M1
IRF7811A
D_B
CMDSH-3
+ _4.7µF
6.3V
C_F
0.1µF
L1
1µH
V_OUT
1.05V TO 1.825V
15A
M2
IRF7811A
×2
R_SENSE ^UPS840
0.003Ω
+ ^COUT
270µF
2V
×3
SGND
3720 F08
Figure 8. 15A CPU Core Voltage Regulator with Active Voltage Positioning at 300kHz
V_OUT
100mV/DIV
1.5V
V_OUT
100mV/DIV
1.5V
I_L
10A/DIV
C_OUT = 5 × 270µF
V_IN = 15V
FIGURE 7 CIRCUIT
20µs/DIV
3720 F09
Figure 9. Normal Transient Response (C_OUT = 5 × 270µF)
I_L
10A/DIV
C_OUT = 3 × 270µF
V_IN = 15V
FIGURE 8 CIRCUIT
20µs/DIV
3720 F10
Figure 10. Transient Response with Active
Voltage Positioning (C_OUT = 3 × 270µF)
3720f
21