LTC1735 Linear Technology, LTC1735 Datasheet - Page 22

• Manufacturer Part Number: LTC1735
• Description: High Efficiency Synchronous Step-Down Switching Regulator
• Manufacturer: Linear Technology

APPLICATIO S I FOR ATIO
LTC1735
voltage cannot exceed 0.082V. At V
maximum output voltage change controlled by the I
would be:
With the optimum resistor values at the I
voltage will swing from 1.55V at minimum load to 1.44V
at full load. At this output voltage, active voltage position-
ing provides an additional 56mV to the allowable tran-
sient voltage on the output capacitors, a 68% improve-
ment over the 82mV allowed without active voltage
positioning.
The next step is to calculate the I
factor. The V
22
100pF
0.1 F
47pF
C5
C2
C4
V
100k
27k
R1
R2
OSENSE
100pF
39pF
1000pF
C1
C3
C6
ITH
Input Offset V
scale factor reflects the I
0 03
1
2
3
4
5
6
7
8
U
.
0 8
C
RUN/SS
I
FCB
SGND
V
SENSE
SENSE
TH
.
OSC
OSENSE
V
V
V
REF
LTC1735
• .
–
+
680k
100k
U
R3
R4
1 5
U1
Figure 8. CPU-Core-Voltage Regulator with Active Voltage Positioning
•
EXTV
BOOST
INTV
PGND
OUT
TH
SW
V
BG
TG
CC
CC
IN
56
pin voltage, V
16
15
14
13
12
11
10
9
W
mV
5V (OPTIONAL)
TH
OUT
pin, the output
TH
C9
1 F
D1
CMDSH-3
= 1.5V, the
pin voltage
U
+
C8
0.22 F
ITH
C7
0.1 F
, scale
TH
C10
4.7 F
10V
pin
M1
FDS6680A
MBRS340
M2, M3
FDS6680A
2
required for a given load current. V
sense resistor voltage, which represents the DC output
current plus one half of the peak-to-peak inductor current.
The no load to full load V
which controls the sense resistor voltage from 0V to the
factor with a 0.003 sense resistor is:
V
V
ITH
V
ITH
SENSE(MAX)
V
D2
ITH
at any load current is:
Scale Factor
C9, C19: TAIYO YUDEN JMK107BJ105
C10: KEMET T494A475M010AS
C12 TO C14: TAIYO YUDEN GMK325F106
C15 TO C18: PANASONIC EEFUE0G181R
D1: CENTRAL SEMI CMDSH-3
D2: MOTOROLA MBRS340
L1: PANASONIC ETQP6F1R0SA
M1 TO M3: FAIRCHILD FDS6680A
R5: IRC LRF2512-01-R003-J
U1: LINEAR TECHNOLOGY LTC1735CS
1 H
L1
V
I
ITH
OUTDC
voltage of 75mV. The calculated V
Offset
0.003
R5
( .
V
2 4
ITH
2
I
L
V
ITH
Range Sense
1735 F08
– .
C11
330pF
11.5k
•
0 075
10k
0 3
range is from 0.3V to 2.4V,
.
V
R6
R7
ITH
V
•
V
+
) • .
V
Scale Factor
SENSE MAX
ITH
0 003
C15 TO
C18
180 F
4V
controls the peak
(
C12 TO C14
10 F
35V
Re
sistor Value
)
0 084
C19
1 F
.
ITH
V
7.5V TO
24V
GND
V
1.5V
15A
GND
scale
V A
IN
OUT
/