LTC1735
U
W U U
APPLICATIO S I FOR ATIO
R3
680k
V
IN
7.5V TO
24V
C12 TO C14
10µF
35V
R1
27k
R4
C7
0.1µF
100k
C9, C19: TAIYO YUDEN JMK107BJ105
C10: KEMET T494A475M010AS
C12 TO C14: TAIYO YUDEN GMK325F106
C15 TO C18: PANASONIC EEFUE0G181R
D1: CENTRAL SEMI CMDSH-3
C1
GND
39pF
1
2
3
4
5
6
7
8
16
15
14
13
12
11
10
9
M1
C
TG
BOOST
SW
OSC
FDS6680A
C2
0.1µF
D2: MOTOROLA MBRS340
L1: PANASONIC ETQP6F1R0SA
M1 TO M3: FAIRCHILD FDS6680A
R5: IRC LRF2512-01-R003-J
RUN/SS
C3
100pF
C8
0.22µF
R2
100k
U1: LINEAR TECHNOLOGY LTC1735CS
I
TH
C4
100pF
U1
LTC1735
L1
1µH
R5
0.003Ω
D1
CMDSH-3
V
1.5V
15A
OUT
FCB
SGND
V
V
IN
C11
330pF
D2
C19
1µF
INTV
CC
MBRS340
C5
47pF
R6
10k
M2, M3
FDS6680A
×2
C15 TO
+
BG
OSENSE
C18
180µF
4V
C10
4.7µF
10V
+
R7
C9
1µF
11.5k
–
GND
SENSE
PGND
C6
1000pF
+
SENSE
EXTV
5V (OPTIONAL)
CC
1735 F08
Figure 8. CPU-Core-Voltage Regulator with Active Voltage Positioning
voltage cannot exceed ±0.082V. At VOUT = 1.5V, the
maximum output voltage change controlled by the ITH pin
would be:
voltage required for a given load current. VITH controls the
peak 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 VITH range is from 0.3V to
2.4V, which controls the sense resistor voltage from 0V to
the ∆VSENSE(MAX) voltage of 75mV. The calculated VITH
scale factor with a 0.003Ω sense resistor is:
Input Offset • VOUT
∆VOSENSE
=
=
VREF
±0.03V •1.5
0.8V
= ±56mV
V
ITH Range • SenseResistor Value
VITH ScaleFactor =
∆VSENSE(MAX)
With the optimum resistor values at the ITH pin, the output
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.
(2.4V – 0.3V)• 0.003
=
= 0.084V/A
0.075V
VITH at any load current is:
∆IL
2
VITH = IOUTDC
+
• VITH ScaleFactor
The next step is to calculate the scale factor for VITH, the
ITH pin voltage. The VITH scale factor reflects the ITH pin
+VITH Offset
1735fc
23
Linear [ Linear ]
