lm26484sqx National Semiconductor Corporation, lm26484sqx Datasheet - Page 15

• Manufacturer Part Number: lm26484sqx
• Description: Power Management Unit
• Manufacturer: National Semiconductor Corporation

I
I
SUGGESTED INDUCTORS AND THEIR SUPPLIERS
OUTPUT CAPACITOR SELECTION FOR SW1 AND SW2
A ceramic output capacitor of 10 µF, 6.3V is recommended
with an ESR of about 2 mΩ or less.
Output ripple can be estimated from the vector sum of the
reactive (Capacitor) voltage component and the real (ESR)
voltage component of the output capacitor.
V
V
V
The output capacitor needs to be mounted as close as pos-
sible to the output pin of the device.
The output filter capacitor smooths out current flow from the
inductor to the load, helps maintain a steady output voltage
during transient load changes and reduces output voltage
ripple. These capacitors must be selected with sufficient ca-
pacitance and sufficiently low ESR to perform these functions.
Note that the output voltage ripple is dependent on the induc-
tor current ripple and the equivalent series resistance of the
output capacitor (ESR
dent as well as temperature dependent. The R
calculated with the applicable switching frequency and ambi-
ent temperature.
SAT
LPEAK
Inductor
L1 and L2
LPS4414–501ML
COUT
ROUT
PPOUT
:
:
:
:
Model
:
Inductor saturation current at operating tempera-
ture
Peak inductor current during worst case conditions
Estimated reactive output ripple
Estimated real output ripple
Estimated peak-to-peak output ripple
Coilcraft
Vendor
Value
0.5
COUT
). ESR
4.3 x 4.3 x 1.4
Dimensions
COUT
Unit
µH
(mm)
30066106
is frequency depen-
ESR
DCR (max)
Description
SW1 and SW2 inductor
50 mΩ
should be
15
I
I
V
V
L:
F:
D:
EFF:
I
transients, startup, high temperature, worst case conditions,
etc.
INPUT CAPACITOR SELECTION FOR SW1 AND SW2
It is required to use a ceramic input capacitor of at least 10
μF and 6.3V with an ESR of under 10 mΩ.
The input power source supplies average current continu-
ously. During the PFET switch on-time, however, the de-
manded di/dt is higher than can be typically supplied by the
input power source. This delta is supplied by the input capac-
itor.
OUTMAX
RIPPLE
SAT
OUT
IN
:
may not be exceeded during any operation, including
:
:
: Maximum average inductor current
Peak-to-Peak inductor current
Output voltage
Input voltage
Inductor value in Henries at I
Switching frequency, Hertz
Estimated duty factor
Estimated power supply efficiency
Notes
D.C.R. 50 mΩ
OUTMAX
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