LTC3703IGN-5 Linear Technology, LTC3703IGN-5 Datasheet - Page 8

• Manufacturer Part Number: LTC3703IGN-5
• Description: IC,SMPS CONTROLLER,VOLTAGE-MODE,CMOS,SSOP,16PIN,PLASTIC
• Manufacturer: Linear Technology

LTC3703
FU CTIO AL DIAGRA
OPERATIO
The LTC3703 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 100V without the need for a step-down transformer.
For circuit operation, please refer to the Functional Dia-
gram of the IC and Figure 1. The LTC3703 uses voltage
8
R2
U
MODE/SYNC
R1
V
C
CC
SS
RUN/SS
(<15V)
COMP
V
V
FB
CC
IN
16
12
U
5
1
3
4
0.8V
3.2V
C
VCC
U
4µA
+
+
–
OVER
TEMP
OT SD
FB
(Refer to Functional Diagram)
1V
–
+
÷
DETECT
SYNC
UVSD OTSD
REFERENCE
BANDGAP
W
0.8V
% DC
LIMIT
EXT SYNC
FORCED CONTINUOUS
–
PWM
+
FSET
CHIP
SD
INTERNAL
3.2V V
OSC
0.76V
2
V
+
MIN
CC
RSET
CC
–
0.84V
+
MAX
–
UVLO
UV SD
mode control in which the duty ratio is controlled directly
by the error amplifier output and thus requires no current
sense resistor. The V
feedback and is compared to the internal 0.8V reference by
the error amplifier, which outputs an error signal at the
COMP pin. When the load current increases, it causes a
drop in the feedback voltage relative to the reference. The
COMP voltage then rises, increasing the duty ratio until the
INV
OVERCURRENT
DRIVE
LOGIC
–
–
CURRENT
+
+
REVERSE
50mV
±
+
–
12µA
FB
pin receives the output voltage
±
GN16
INV
15
14
13
11
10
5
9
6
8
I
BOOST
TG
SW
DRV
BG
BGRTN
INV
GND
MAX
R
CC
MAX
V
3703 FD
CC
D
C
B
B
C
OUT
V
IN
L1
M1
M2
3703fa
V
OUT