Datasheet

]A[
fL2
DV
+
D
¿
I
=I
SW
IN
OUT
pk_L
K
x
xx
]A[
2
I
+I=I
L
AVE_Lpk_L
'
OUT
INOUT
V
VV
=D
-
x
],A[
fL
DV
=I
SW
IN
L
'
x
],
x
OUT
IN
V
V
=
'D
A[
D
¿
I
=I
OUT
AVE_L
K
I
OUT_Max
=
V
OUT
1.32 x V
IN
- 2.79
[A]
LM4510
SNVS533C –SEPTEMBER 2007–REVISED MAY 2013 www.ti.com
Table 1. Suggested Component Values for Different Output Voltages
Output Voltage (V) R
F2
(kΩ) R
F1
(kΩ) R
C
(kΩ) C
C1
(nF)
16 20.5 240 46.4 2.2
12 20.5 174 46.4 2.2
5 20.5 60.4 46.4 2.2
3.3 20.5 33 46.4 2.2
MAXIMUM OUTPUT CURRENT
When the output voltage is set at different level, it is important to know the maximum load capability. By first
order estimation, I
OUT(MAX)
can be estimated by the following equation:
(2)
INDUCTOR SELECTION
The larger value inductor makes lower peak inductor current and reduces stress on internal power NMOS.
On the other hand, the smaller value inductor has smaller outline, lower DCR and a higher current capacity.
Generally a 4.7 μH to 15 μH inductor is recommended.
I
L_AVE
CHECK
The average inductor current is given by the following equation:
(3)
Where I
OUT
is output current, η is the converter efficiency of the total driven load and D’ is the off duty cycle of the
switching regulator.
Inductor DC current rating (40°C temperature rise) should be more than the average inductor current at worst
case.
ΔI Define
The inductor ripple current is given by the following equations:
(4)
Where D is the on-duty cycle of the switching regulator. A common choice is to set ΔI
L
to about 30% of I
L_AVE
.
I
L_PK
≤ I
CL
Check & I
MIN
Define
The peak inductor current is given by the following equation:
(5)
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