Datasheet

LT3505
15
3505fc
APPLICATIONS INFORMATION
V
IN
BOOST
GND
SW
V
IN
LT3505
(6a)
D2
V
OUT
C3
V
BOOST
– V
SW
≅ V
OUT
MAX V
BOOST
≅ V
IN
+ V
OUT
3505 F06a
V
IN
BOOST
GND
SW
V
IN
LT3505
(6b)
D2
3505 F06b
V
OUT
C3
V
BOOST
– V
SW
≅ V
IN
MAX V
BOOST
≅ 2V
IN
Figure 6. Two Circuits for Generating the Boost Voltage
10µF
32.4k
I
LOAD
1A/DIV
V
OUT
20mV/DIV
AC COUPLED
I
LOAD
1A/DIV
V
OUT
20mV/DIV
AC COUPLED
10µs/DIV
10µs/DIV
I
LOAD
1A/DIV
V
OUT
20mV/DIV
AC COUPLED
10µs/DIV
10.0k
100k
22pF
22pF
V
OUT
3505 F05a
3505 F05b
3505 F05c
V
OUT
32.4k
10.0k
10µF
×2
44pF
32.4k
66pF
KEMET
A700D127M006ATE015
V
OUT
+
10.0k
120µF
FB
V
C
100k
22pF
FB
V
C
301k
22pF
FB
V
C
Figure 5. Transient Load Response of the LT3505 with Different Output Capacitors as the
Load Current is Stepped from 500mA to 1.2A. V
IN
= 12V, V
OUT
= 3.3V, L = 2µH, R
T
= 20.0k