ST1S14 STMicroelectronics, ST1S14 Datasheet - Page 22

• Manufacturer Part Number: ST1S14
• Description: Up to 3 A step down switching regulator
• Manufacturer: STMicroelectronics

Application information
7.1.3
22/42
Equation 21
A list of some tantalum capacitor manufacturers is provided in
selection.
Table 9.
1. see
2. POSCAP capacitors have some characteristics which are very similar to tantalum.
Inductor
The inductor value is very important as it fixes the ripple current flowing through the output
capacitor. The ripple current is usually fixed at 20 - 40% of I
I
Equation 22
where T
V
current through the inductor is given by:
Equation 23
and it can be observed that if the inductor value decreases, the peak current (which must be
lower than the current limit of the device) increases. So, when the peak current is fixed, a
higher inductor value allows a higher value for the output current. In the
selection, some inductor manufacturers are listed.
Table 10.
O
Nippon Chemicon
Sanyo POSCAP
AVX
Wurth Elektronik
Coilcraft
OUT
max = 3 A. The approximate inductor value is obtained using the following formula:
Manufacturer
Manufacturer
= 3.3 V, V
Chapter 6: Closing the loop
ON
is the ON time of the internal switch, given by D · T. For example, with
Output capacitor selection
Inductor selection
(2)
IN
= 24 V and ΔI
THB/C/E
Series
KZE
TPS
TAE
WE-HCI 7040
WE-HCI 7050
for the selection of the output capacitor
f
Z
XPL 7030
Doc ID 17977 Rev 1
Series
O
=
= 0.8 A, the inductor value is about 4.7 µH. The peak
L
------------------------------------------------- -
2 π ESR COUT
=
⋅ ⋅
Rated voltage (V) Cap value (µF)
(
---------------------------------- T
I
V
PK
IN
6.3 to 50
1
=
–
4 to 16
4 to 16
4 to 35
ΔI
V
⋅
I
O
OUT
+
Inductor value (µH)
ΔI
---- -
2
)
⋅
<
ON
4.9 to 10
2.2 to 10
BW
1 to 4.7
<
f
-------- -
f
omax
SW
5
Z
=
Table 9.: Output capacitor
, which is 0.6 - 1.2 A with
------------------------------------------------- -
2 π ESR COUT
⋅ ⋅
Saturation current (A)
(1)
Table 10.: Inductor
1
⋅
20 to 4.0
29 to 7.2
ESR (mΩ)
20 to 7
<
ST1S14
BW
(1)