LT3798
PIN FUNCTIONS
GATE (Pin 14):
N-Channel FET Gate Driver Output. Switches
between INTV
CC
and GND. Driven to GND during shutdown
state and stays high during low voltage states.
SENSE (Pin 15):
The Current Sense Input for the Control
Loop. Kelvin connect this pin to the positive terminal of the
switch current sense resistor, R
SENSE
, in the source of the
NFET. The negative terminal of the current sense resistor
should be connected to the GND plane close to the IC.
V
IN_SENSE
(Pin 16):
Line Voltage Sense Pin. The pin is
used for sensing the AC line voltage to perform power
factor correction. Connect a resistor in series with the
line voltage to this pin. If no PFC is needed, connect this
pin to INTV
CC
with a 25k resistor.
GND (Exposed Pad Pin 17):
Ground. The exposed pad
of the package provides both electrical contact to ground
and good thermal contact to the printed circuit board.
The exposed pad must be soldered to the circuit board
for proper operation.
BLOCK DIAGRAM
D2
R13
L1C
C1
R5
R15
DCM
R14
EN/UVLO
V
IN_SENSE
V
IN
N:1
C3
L1A
L1B
V
RECTIFIED
R3
R1
C2
D1
V
OUT
+
C7
V
OUT
–
R4
T1
STARTUP
INTERNAL REG
1.22V
–
A7
+
R7
INTV
CC
C5
+
A2
–
+
R8
V
REF
OVP
COMP
+
C6
COMP
–
CTRL1
CTRL2
CTRL3
S&H
FB
1.22V
VC
FB
R12
1M
SW1
S&H
A9
600mV
ONE
SHOT
CURRENT
COMPARATOR
–
A3
+
A1
–
S
S
MASTER
LATCH
A4
LOW OUTPUT
CURRENT
OSCILLATOR
R
Q
R11
GATE
R9
DRIVER
SENSE
R6
–
A5
+
GND
MINIMUM
A6
MULTIPLIER
+
A8
–
R10
C4
3798 BD
3798f
7
LINER [ LINEAR TECHNOLOGY ]
