LTC3703-5
8
37035fa
FU CTIO AL DIAGRA
U
U
W
5
1
UVSD OTSD
CHIP
SD
1V
3.2V
4
µ
A
RUN/SS
BANDGAP
SYNC
DETECT
OVER
TEMP
V
CC
UVLO
OSC
% DC
LIMIT
DRIVE
LOGIC
+
–
+
–
+
–
+
–
EXT SYNC
FORCED CONTINUOUS
÷
+
+
–
+
–
+
–
+
–
0.8V
MODE/SYNC
3
COMP
4
FB
16
15
14
13
11
10
9
6
12
V
IN
V
CC
(<15V)
INV
PWM
MIN
MAX
0.76V
0.84V
±
OVERCURRENT
12
µ
A
50mV
I
MAX
R
MAX
BOOST
TG
SW
DRV
CC
BG
BGRTN
INV
8
GND
GN16
OT SD
0.8V
REFERENCE
INTERNAL
3.2V V
CC
UV SD
2
FSET
37035 FD
REVERSE
CURRENT
FB
RSET
5
C
SS
R2
R1
V
CC
C
VCC
D
B
C
B
V
CC
V
IN
M1
M2
C
OUT
V
OUT
L1
INV
±
OPERATIO
U
(Refer to Functional Diagram)
The LTC3703-5 is a constant frequency, voltage mode
controller for DC/DC step-down converters. It is designed
to be used in a synchronous switching architecture with
two external N-channel MOSFETs. Its high operating volt-
age capability allows it to directly step down input voltages
up to 60V without the need for a step-down transformer.
For circuit operation, please refer to the Functional
Diagram of the IC and the circuit on the first page of this
data sheet. The LTC3703-5 uses voltage mode control in
which the duty ratio is controlled directly by the error
amplifier output and thus requires no current sense resis-
tor. The V
FB
pin receives the output voltage feedback and
is compared to the internal 0.8V reference by the error
amplifier, which outputs an error signal at the COMP pin.
