AN3352 Datasheet, PDF (13/26 Pages) STMicroelectronics – Dual LNB power supply based on the LNBH24L

AN3352
Component selection guidelines
V_UPmax = V_OUTmax + V_DROP = 19.2 V + 0.75 V = 19.95 V
I_OUTmax = 500 mA
Eff = 90% (worst-case in these conditions)
Based on Equation 1 and the preceding application conditions, I_PEAK is:
Equation 2
Ipeak
=
19.95 ∗ 0.5
0.9 ∗11
+
2
*
22
11
* 10^−6 *
220
* 10³
⎜⎛1−
⎝
11
19.95
⎟⎞
⎠
=
1.52A
Then, in this example, an inductor with saturation current > 1.52 A should be recommended.
Several inductors suitable for the LNBH24L are listed in Table 5, although there are many
other manufacturers and devices that can be used. Consult each manufacturer for more
detailed information and for their entire selection of related parts, as many different shapes
and sizes are available. Ferrite core inductors should be used to obtain the best efficiency.
Choose an inductor that can handle at least the I_PEAK current without saturating, and ensure
that the inductor has a low DCR (copper wire resistance) to minimize power losses and,
consequently, to maximize the total efficiency.
Table 5. Recommended Inductors
Vendor
Part number
Sumida
Toko
CD104-220MC
RHC110-220M
822LY-220K
824LY-220K
A671HN-220L
A814LY-220M
Panasonic
ELC08D220E
ELC10D220E
Coilcraft
DC1012-223
PVC-0-223-03
DO3316P-223
I_SAT (A)
1.6
2.4
1.3
1.72
2.44
2.0
1.8
3.2
2.5
3
2.6
DRC (m?)
67
88
70
76
21
75
51
40
46
35
85
Mounting type
SMD
Through-hole
Through-hole
Through-hole
Through-hole
SMD
Through-hole
Through-hole
Through-hole
Through-hole
SMD
2.2
Output current limit selection (R2-RSEL)
The linear regulator current limit threshold can be set through an external resistor connected
to the I_SEL pin. The resistor value defines the typical output current threshold limit by the
equation:
Equation 3
Im ax( A) = ¹⁰⁰⁰⁰
Rsel
Doc ID 018526 Rev 3
13/26