鈮?/div>
3.366)
Output current: 8 A (maximum, steady state), 10 A (surge, 10 ms duration, 10% duty cycle maximum)
Output ripple: 33 mV
P-P
at 8 A
Output load response: 0.3 V => 10% to 90% step load change, from 1 A to 7 A
Operating temperature: 鈭?0擄C to 85擄C
f
SW
=300 kHz
V
O(min)
V
O(max)
V
IN(min)
1. Calculate maximum and minimum duty cycles
d
MIN
+
+
3.324
+
0.135
24
V
IN(max)
2. Select switching frequency
The switching frequency is based on the minimum duty cycle ratio and the propagation delay of the current limit
comparator. In order to maintain current limit capability, the on time of the upper MOSFET, t
ON
, must be greater
than 300 ns (see Electrical Characteristics table). Therefore
V
O(min)
V
IN(max)
+
t
ON
T
SW
or
(47)
V
O(min)
T
SW
1
+
f
SW
+
V
IN(max)
T
ON
(48)
Using 400 ns to provide margin,
f
SW
+
0.135
+
337 kHz
400 ns
Since the oscillator can vary by 10%, decrease f
SW
, by 10%
f
SW
+
0.9
337 kHz
+
303 kHz
(49)
d
MAX
+
+
3.366
+
0.337
10
(46)
and therefore choose a frequency of 300 kHz.
3. Select
鈭咺
In this case
鈭咺
is chosen so that the converter enters discontinuous mode at 20% of nominal load.
DI
+
I
O
2
0.2
+
8
2
0.2
+
3.2 A
(50)
26
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