LT3592
APPLICATIONS INFORMATION
their maximum voltage capability. If a capacitor with a
lower voltage rating is found to not be stable in a design,
it will often result in a smaller solution to choose a larger
capacitor value of the same voltage rating than to choose
one of the same capacitance and higher voltage rating. For
example, a 10μF, 10V ceramic capacitor might be smaller
than a 4.7μF, 16V part, if a 4.7μF, 10V capacitor is found
to not be adequate in a given application. The LT3592HV
can tolerate sustained output voltages of up to 25V. For
output voltages above 12V, use an external Schottky diode
for the boost circuit with the anode tied to CAP and the
cathode tied to BOOST (as shown in Figure 13).
900kHz with a 6.8μH inductor and a 4.7μF ceramic output
capacitor. The LT3592 is in BRIGHT (500mA) mode but
the current load is switched from 50mA to 450mA and
back, so the current control loop is not active for either
current level and the output voltage is regulated through
the resistive voltage divider to the FB pin.
Other Linear Technology Publications
Application Notes AN19, AN35, and AN44 contain more
detaileddescriptionsanddesigninformationforStep-down
regulatorsandotherswitchingregulators.TheLT1376data
sheet has an extensive discussion of output ripple, loop
compensation, and stability testing. Design Note DN100
shows how to generate a bipolar output supply using a
Step-down regulator.
Transient Performance with Voltage Control Loop
Thevoltagecontrollooptransientcharacteristicsaresimilar
to, but not identical to the current control loop. Figure 12
shows the transient for a 12V input application running at
I
LED
200mA/DIV
V
OUT
1V/DIV
V
SW
10V/DIV
3592 F12
10μs/DIV
Figure 12. Switching Transient When Going from 50mA to 500mA Current and Back in Voltage Mode
D2
BOOST
C3
CAP
LT3592 SW
V
BATT
IN
GND
DA
3592 F13
Figure 13. Boost Circuit with External Schottky Diode for Output Voltages Above 12V
3592fc
20
Linear Systems [ Linear Systems ]
