lt3686a Linear Technology Corporation, lt3686a Datasheet - Page 24

• Manufacturer Part Number: lt3686a
• Description: 37v/1.2a Step-down Regulator In 3mm
• Manufacturer: Linear Technology Corporation

LT3686A
APPLICATIONS INFORMATION
Outputs Greater Than 19V
Note that for outputs above 19V, the input voltage range
will be limited by the maximum rating of the BOOST pin.
The sum of input and output voltages cannot exceed the
BOOST pin’s 55V rating. The 25V circuit (Figure 18) shows
how to overcome this limitation using an additional Zener
diode.
Other Linear Technology Publications
Application Notes 19, 35 and 44 contain more detailed
descriptions and design information for Buck regulators
and other switching regulators. The LT1376 data sheet
has a more extensive discussion of output ripple, loop
compensation and stability testing. Design Note 318
shows how to generate a bipolar output supply using a
buck regulator.
TYPICAL APPLICATIONS
24
3.6V TO 25V
V
IN
2.2μF
1nF
0.8V Step-Down Converter
61.9k
V
EN/UVLO
SYNC/MODE
SS
RT
IN
LT3686A
GND
3.6V TO 25V
BOOST
SW
BD
DA
FB
V
IN
2.2μF
1nF
0.22μF
2.2μH
3686A TA02a
1.8V Step-Down Converter
61.9k
100μF
V
0.8V
1.2A
EN/UVLO
SYNC/MODE
V
SS
RT
OUT
IN
LT3686A
GND
30V TO 36V
BOOST
5V TO 37V
SW
BD
DA
FB
V
IN
100n
V
2.2μ
IN
2.2μF
1nF
0.22μF
10k
12.4k
Figure 18. 25V Step-Down Converter
3.3μH
3686A TA02c
61.9k
3.3V Step-Down Converter
61.9k
EN/UVLO
SYNC/MODE
V
SS
RT
IN
47μF
EN/UVLO
SYNC/MODE
V
1.8V
1.2A
V
SS
RT
IN
OUT
LT3686A
GND
LT3686A
GND
BOOST
BOOST
SW
BD
DA
FB
SW
BD
DA
FB
10k
0.22μF
10k
15V
0.22μF
31.6k
100μH
301k
6.8μH
3686A TA02b
3686A F18
0.22μF
22μF
V
3.3V
1.2A
10μF
V
500mA
OUT
3686af
OUT