LT3501EFE Linear Technology, LT3501EFE Datasheet - Page 22

• Manufacturer Part Number: LT3501EFE
• Description: IC,SMPS CONTROLLER,CURRENT-MODE,BIPOLAR,TSSOP,20PIN,PLASTIC
• Manufacturer: Linear Technology

APPLICATIONS INFORMATION
inductor size by allowing an increase in frequency. A dual
step down application (Figure 10) steps down the input
voltage (V
voltage to power the second output (V
able to provide enough current for its output plus V
maximum load. Note that the V
minimum input voltage (2V) when the second channel
starts to switch. Delaying channel 2 can be accomplished
by either independent soft-start capacitors or sequencing
with the PG1 output.
For example, assume a maximum input of 24V:
V
LT3501
22
IN
Frequency Hz
L
= 24V, V
≥
(
V
I I N
IN1
PMEG4005
–
OUT1
) to the highest output voltage then uses that
V
V
V
( )
OUT
IN
OUT1
5V
= 5V at 1.5A and V
•
)
f
≤
•
V
V
OUT
IN
8.06k
47µF
V
Figure 10. 5V and 1.2V 2-Stage Step-Down Converter with Output Sequencing
t
OUT
–
MIN ON
V
SW
10pF
42.3k
(
6V TO 24V
+
OUT1
V
+
)
D
3.3µH
V
V
IN
D
OUT2
must be above V
IN2
40.2k
). V
470pF
= 1.2V at 1.5A
4.7µF
B360A
OUT1
0.47µF
0.1µF
must be
SHDN
BST1
SW1
IND1
V
PG1
FB1
V
SS/TRACK1
OUT1
C1
V
IN1
OUT2
IN2
LT3501
GND
SS/TRACK2
Single Step Down:
2-Stage Step-Down:
V
V
IN2
BST2
FSET
IND2
SW2
OUT2
PG2
FB2
V
Frequency Hz
L
L
Frequency
Max Fr
L
L
C2
1
2
1
2
PMEG4005
=
=
=
= =
26.7k
24 392
24 1 2
(
(
(
(
0.1µF
24 1 2 1 2
5 1 2 1 2
24 5 5
24 5 5
2
5 1 2
e e quency
100k
0.47µF
•
• .
– . • .
4 4 392
• .
B360A
– . • .
–
–
•
≤
( )
32.4k
)
)
MHz
470pF
)
MHz
kHz
24 0 4 0 6
•
•
)
1µH
kHz
≤
=
– .
5 0 6
4k
190
≥
≥
1 2
24 0 4 0 6
+
3501 F10
10pF
.
10
≥
3 3
8.06k
1 2 0 6
≥
ns
. µ
– .
MHz
0 76
.
.
190
+
µ
2 7
.
H
.
+
H
47µF
×2
.
ns
µ
µ
+
.
H
H
=
V
1.2V
1 2
.
OUT2
.
=
MHz
392 z z
kH
3501fb