LT8300
19
8300f
applicaTions inForMaTion
Step 7: Select the EN/UVLO Resistors.
Determine the amount of hysteresis required and calculate
R1 resistor value:
V
IN(HYS)
= 2.5µA • R1
Example:
Choose 2.5V of hysteresis,
R1 = 1M
Determine the UVLO thresholds and calculate R2 resistor
value:
V
IN(UVLO+)
=
R2
+ 2.5µA • R1
Example:
Set V
IN
UVLO rising threshold to 34.5V,
R2 = 40.2k
V
IN(UVLO+)
= 34.1V
V
IN(UVLO–)
= 31.6V
Step 8: Ensure minimum load.
The theoretical minimum load can be approximately
estimated as:
I
LOAD(MIN)
=
300µH •(52mA)
2
• 7.5kHz
2 • 12V
= 0.25mA
Remember to check the minimum load requirement in real
application. The minimum load occurs at the point where
the output voltage begins to climb up as the converter
delivers more energy than what is consumed at the out-
put. The real minimum load for this application is about
0.6mA, 0.5% of 120mA maximum load. In this example,
a 20k resistor is selected as the minimum load.
