Datasheet

LT3502/LT3502A
16
3502fd
applications inForMation
Figure 7. To Soft-Start the LT3502A, Add a Resistor and Capacitor to the SHDN Pin
Figure 8b. Diode D4 Prevents a Shorted Input from Discharging
a Backup Battery Tied to the Output; it Also Protects the Circuit
from a Reversed Input. The LT3502/LT3502A Runs Only When
the Input is Present
V
IN
3502 F08b
SHDN
BOOST
SW
LT3502A
BD
D4
GND
DA
FB
V
IN
V
OUT
+
Figure 8a. The LT3502A Reduces its Frequency to Below 500kHz
to Protect Against Shorted Output with 40V Input
V
SW
10V/DIV
2µs/DIVV
IN
= 40V
V
OUT
= 0V
L = 6.8µH
C
OUT
= 10µF
3502 F08a
I
L
500mA/DIV
RUN
V
SW
10V/DIV
V
IN
= 12V
V
OUT
= 3.3V
L = 6.8µH
C
OUT
= 10µF
V
OUT
2V/DIV
5µs/DIV
I
L
500mA/DIV
V
SW
10V/DIV
V
IN
= 12V
V
OUT
= 3.3V
L = 6.8µH
C
OUT
= 10µF
V
OUT
2V/DIV
50µs/DIV
3502 F07
I
L
500mA/DIV
SHDN
GND
3502 F07a
RUN
50k
0.1µF
SHDN
GND
3502 F07b