Datasheet

LT3798
7
3798fa
PIN FUNCTIONS
BLOCK DIAGRAM
V
OUT
+
V
OUT
–
V
RECTIFIED
D1
C7
L1A
T1
N:1
L1B
C2
SW1
R1
R3
C3
1.22V
V
IN
R14
R13
D2
L1C
•
C1
R15
R4
R5
V
IN_SENSE
EN/UVLODCM
STARTUP
INTERNAL REG
V
REF
OVP
FB
S&H
COMP
+
COMP
–
CTRL1
CTRL3
CTRL2
FB
S&H
V
C
1.22V
C6
C4
R8
R9
R10
+
–
A8
–
+
A5 A6
MINIMUM
MULTIPLIER
A3
R12
1M
+
–
600mV
ONE
SHOT
+
–
A2
+
–
A1
CURRENT
COMPARATOR
R
Q
S
S
MASTER
LATCH
LOW OUTPUT
CURRENT
OSCILLATOR
A4
R11
R7
DRIVER
GND
GATE
INTV
CC
SENSE
R6
C5
3798 BD
–
+
A7
A9
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.