Datasheet
L1 10 PH
D1
C
SS
R
S
C
IN
C
BYP
R
T
118 k:
10 k:
0.022 PF
80 m:
5V
FB
SW
LM25011
BST
CS
RT
VIN
SS
SGND
PGD
CSG
8V to 36V
Input
4.7 PF
0.1 PF
R
PGD
V
PGD
Power
Good
4.99 k:
R
FB2
C
BST
C
OUT
R
FB1
V
OUT
4.99 k:
0.1 PF
10 PF
C
SS
=
2.51V
5 ms x 10 PA
= 0.02 PF
LM25011, LM25011-Q1
www.ti.com
SNVS617G –APRIL 2009–REVISED FEBRUARY 2013
C
SS
: The capacitor at the SS pin determines the soft-start time, i.e. the time for the output voltage to reach its
final value (t1 in Figure 17). For a soft-start time of 5 ms, the capacitor value is determined from the following:
(21)
D1: A Schottky diode is recommended. Ultra-fast recovery diodes are not recommended as the high speed
transitions at the SW pin may affect the regulator’s operation due to the diode’s reverse recovery transients. The
diode must be rated for the maximum input voltage, the maximum load current, and the peak current which
occurs when the current limit and maximum ripple current are reached simultaneously. The diode’s average
power dissipation is calculated from:
P
D1
= V
F
x I
OUT
x (1 - D) (22)
where V
F
is the diode’s forward voltage drop, and D is the on-time duty cycle.
FINAL CIRCUIT
The final circuit is shown in Figure 21, and its performance is shown in Figure 22 and Figure 23. The current limit
measured approximately 1.62A at Vin = 8V, and 1.69A at Vin = 36V.
Figure 21. Example Circuit
Figure 22. Efficiency (Circuit of Figure 21) Figure 23. Frequency vs V
IN
(Circuit of Figure 21)
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