LTC3727EG 查看數據表（PDF） - Linear Technology
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LTC3727EG Datasheet PDF : 32 Pages
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FU CTIO AL DIAGRA
LTC3727/LTC3727-1
PLLIN
FIN
50k
PLLFLTR
RLP
CLP
PGOOD
PHASE DET
DUPLICATE FOR SECOND
CONTROLLER CHANNEL
INTVCC
VIN
BOOST
DB
OSCILLATOR
CLK1
CLK2
0.86V
VOSENSE1
0.74V
0.86V
VOSENSE2
DROP
OUT
DET
SQ
RQ
BOT FCB
TOP ON
TG
TOP
SW
SWITCH
LOGIC
INTVCC
BG
BOT
0.55V
+B
–
SHDN
PGND
CB
+
D1
CIN
COUT
RSENSE
VSEC
1.5V
0.18µA
R6
FCB
R5
7V –
+
+
–
0.74V
BINH
FCB
3.3VOUT
0.8V
VREF
VIN
VIN
EXTVCC
INTVCC
+7.5V
SGND
7.3V +
–
7.5V
LDO
REG
INTERNAL
SUPPLY
I1
I2
–
– ++ –
+
0.86V
3mV
4(VFB)
SLOPE
COMP
25k
25k
2.4V
EA
OV
INTVCC
50k SENSE+
50k SENSE–
VFB
0.80V
VOSENSE
1.2µA
6V
0.86V
SHDN
RST
4(VFB)
RUN
SOFT
START
ITH
RUN/SS
DSEC
R2
R1
CC
CC2
RC
CSS
CSEC
VOUT
3727 F02
Figure 2
U
OPERATIO (Refer to Functional Diagram)
Main Control Loop
The LTC3727/LTC3727-1 use a constant frequency, cur-
rent mode step-down architecture with the two controller
channels operating 180 degrees out of phase. During
normal operation, each top MOSFET is turned on when the
clock for that channel sets the RS latch, and turned off
when the main current comparator, I1, resets the RS latch.
The peak inductor current at which I1 resets the RS latch
is controlled by the voltage on the ITH pin, which is the
output of each error amplifier EA. The VOSENSE pin receives
the voltage feedback signal, which is compared to the
internal reference voltage by the EA. When the load current
increases, it causes a slight decrease in VOSENSE relative to
the 0.8V reference, which in turn causes the ITH voltage to
increase until the average inductor current matches the
new load current. After the top MOSFET has turned off, the
bottom MOSFET is turned on until either the inductor
current starts to reverse, as indicated by current compara-
tor I2, or the beginning of the next cycle.
3727f
9
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