Datasheet

LTC3731
10
3731fc
FUNCTIONAL DIAGRAM
PIN FUNCTIONS
V
CC
: Main Supply Pin. This pin supplies the controller
circuit power. In the LTC3731 UH package, it also supplies
the high power pulses to drive the external MOSFET gates.
This pin needs to be very carefully and closely decoupled
to the IC’s PGND pin.
VDR: (LTC3731G Package Only) Supplies power to the
bottom gate drivers only. This pin needs to be very care-
fully and closely decoupled to the IC’s PGND pin.
SWITCH
LOGIC
CLK2
CLK1
SW
SHDN
B
0.55V
3mV
FCB
TOP
BOOST
TG
C
B
C
IN
D
B
PGND
BOT
BG
V
CC
V
CC
(VDR)***
V
IN
+
V
OUT
3731 F02
DROP
OUT
DET
RUN
SOFT-
START
BOT
FORCE BOT
S
R
Q
Q
CLK3
OSCILLATOR
PLLFLTR
50k
0.600V
0.660V
1.5µA
6V
RST
SHDN
FCB
RUN/SS
C
SS
5(V
FB
)
5(V
FB
)
0.86V
SLOPE
COMP
+
–
SENSE
+
V
CC
36k
54k54k
2.4V
SS
CLAMP
I
1
SGND*
0.600V
INTERNAL
SUPPLY
V
CC
C
CC
V
CC
PHASE DET
PLLIN
DUPLICATE FOR SECOND AND THIRD
CONTROLLER CHANNELS
+– +–
R
SENSE
L
C
OUT
+
F
IN
R
LP
C
LP
+
–
+
–
+
–
+
–
IN
+
DIFFOUT
EAIN
V
FB
R1
OV
I
TH
C
C
R
C
IN
–
PGOOD**
FCB
+
–
–
+
+
1.2V
V
REF
UV RESET
V
CC
EAIN
0.66V
RS
LATCH
FCB
0.6V
0.54V
PROTECTION
PHASMD**
CLKOUT
+
–
I
2
SENSE
–
36k
A1
40k40k
40k40k
EA
1.2V
UVADJ
+
–
SHED
R2
*THE LTC3731UH USES THE EXPOSED DIE ATTACH PAD FOR THE SGND CONNECTIONS
**THE PHASMD AND PGOOD PIN FUNCTIONS ARE TIED TOGETHER IN THE LTC3731 UH PACKAGE
***LTC3731CG/IG ONLY
100µs
DELAY
Figure 2