LT3976 Datasheet, PDF (24/28 Pages) Linear Technology – 40V, 5A, 2MHz Step-Down Switching Regulator with 3.3μA Quiescent Current

LT3976
Applications Information
and a SYNC pin resistor to GND added, so that a PG pin
short to either SYNC or RT will form resistor dividers to
keep the voltage on the SYNC and RT pins below their
rated absolute maximum. This application is shown in
Figure 12b. The external Schottky must be connected
such that the absolute maximum of the BOOST pin is not
violated. The SYNC pin resistor can be removed if the
SYNC pin is grounded or PG is left floating both of which
also result in fault tolerant circuits.
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.
V_IN
V_IN BOOST
0.47µF
3.3µH
EN
SW
EXTERNAL
INPUT
10µF
SYNC
LT3976
2Ω
150k
470pF
PG
SS
OUT
RT
FB
10nF
GND
34.9k
1M
316k
10pF
PGOOD
V_OUT
47µF
1210
×2
f = 800kHz
3976 F12a
Figure 12a. Fault Tolerant for V_OUT < 6V
(Note: For V_OUT < 3.3V External Boost Schottky Diode Is Needed)
V_IN
EXTERNAL
INPUT
10µF
V_IN BOOST
EN
SW
SYNC
LT3976
40.2k
PG
SS
OUT
RT
FB
10nF
GND
54.9k
f = 800kHz
0.47µF
3.3µH
2Ω
249k
470pF
PGOOD
316k
1M
10pF
3976 F12b
V_OUT
47µF
1210
×2
Figure 12b. Fault Tolerant for V_OUT < 27V
(Note: For V_OUT < 3V External Boost Schottky Diode
Should Be Connected to the Input)
Figure 12. Two Example Circuits to Achieve Fault Tolerance (FMEA) with the LT3976 QFN Package
3976f
24
For more information www.linear.com/3976