Datasheet

LT3478/LT3478-1
8
34781f
V
IN
V
S
V
C
LED
LED
LED
LED
3478 F01
3
CTRL2
CTRL1
UVLO
INRUSH
CURRENT
PROTECTION
V
REF
10
4
L
5
SS
16
15
R
T
EXPOSED PAD
(GND)
17
OVPSET
TO OVERVOLTAGE
DETECT CIRCUIT
8
V
C
9
SW
1, 2
PWM
14
LED
7
V
OUT
6
SHDN
11
+
+
+
+
+
+
+
1.4V
+
1.05V
1000
R
S
100 R
SENSE
0.1
(INTERNAL FOR
LT3478-1)
R
SENSE
(EXTERNAL FOR
LT3478)
10µA
9.5m
57mV
REF
1.24V
SOFT-START
OVERVOLTAGE
DETECT
OVPSET
12
13
+
PWM
DETECT
OSC SQ Q1
GM
R
SLOPE
COMP
PWM
Σ
+
1V
Q2
BLOCK DIAGRA
W
Figure 1
PI FU CTIO S
UUU
exceeds 6A or V
OUT
exceeds OVP, an internal soft-start
latch is set, the power NPN is immediately turned off and
the SS pin is discharged. The soft-start latch is also set
if V
IN
and/or
S
H
D
N do not meet their turn on thresholds.
The SS pin only recharges when all faults are removed
and the pin has been discharged below 0.25V.
Exposed Pad (Pin 17): The ground for the IC and the con-
verter. The FE package has an Exposed Pad underneath the
IC which is the best path for heat out of the package. Pin 17
should be soldered to a continuous copper ground plane
under the device to reduce die temperature and increase
the power capability of the LT3478/LT3478-1.