參數(shù)資料
型號(hào)： LM26480SQ-BF/NOPB
廠商： NATIONAL SEMICONDUCTOR CORP
元件分類(lèi)： 穩(wěn)壓器
英文描述： 2.4 A SWITCHING REGULATOR, 2400 kHz SWITCHING FREQ-MAX, QCC24
封裝： 4 X 4 MM, 0.80 MM HEIGHT, LLP-24
文件頁(yè)數(shù)： 15/30頁(yè)
文件大?。?/td> 2447K
代理商： LM26480SQ-BF/NOPB
OUTPUT INDUCTORS & CAPACITORS FOR SW1 AND
SW2
There are several design considerations related to the selec-
tion of output inductors and capacitors:
Load transient response;
Stability;
Efficiency;
Output ripple voltage; and
Over-current ruggedness.
The LM26480 has been optimized for use with nominal values
2.2 H and 10 F. If other values are needed for the design,
please contact National Semiconductor sales with any con-
cerns.
INDUCTOR SELECTION FOR SW1 AND SW2
A nominal inductor value of 2.2 H is recommended. It is im-
portant to guarantee the inductor core does not saturate
during any foreseeable operational situation.
Care should be taken when reviewing the different saturation
current ratings that are specified by different manufacturers.
Saturation current ratings are typically specified at 25C, so
ratings at maximum ambient temperature of the application
should be requested from the manufacturer.
There are two methods to choose the inductor saturation cur-
rent rating:
Recommended method:
The best way to guarantee the inductor does not saturate is
to choose an inductor that has saturation current rating
greater than the maximum LM26480 current limit of 2.4A. In
this case the device will prevent inductor saturation.
Alternate method:
If the recommended approach cannot be used, care must be
taken to guarantee that the saturation current is greater than
the peak inductor current:
30040471
I
SAT:
Inductor saturation current at operating tempera-
ture
I
LPEAK:
Peak inductor current during worst case conditions
I
OUTMAX:
Maximum average inductor current
I
RIPPLE:
Peak-to-Peak inductor current
V
OUT:
Output voltage
V
IN:
Input voltage
L:
Inductor value in Henries at I
OUTMAX
F:
Switching frequency, Hertz
D:
Estimated duty factor
EFF:
Estimated power supply efficiency
I
SAT may not be exceeded during any operation, including
transients, startup, high temperature, worst case conditions,
etc.
SUGGESTED INDUCTORS AND THEIR SUPPLIERS
Model
Vendor
Dimensions (mm)
DCR (max)
I
SATURATION
DO3314-222MX
Coilcraft
3.3 x 3.3 x 1.4
200 m
≈1.8A
LPO3310-222MX
Coilcraft
3.3 x 3.3 x 1
150 m
≈1.3A
ELL6PG2R2N
Panasonic
6.0 x 6.0 x 2.0
37 m
≈2.2A
ELC6GN2R2N
Panasonic
6.0 x 6.0 x 1.5
53 m
≈1.9A
CDRH2D14NP-2R2NC
Sumida
3.2 x 3.2 x 1.5
94 m
≈1.5A
Note: Inductor Current Saturation values are estimates; inductor manufacturer should be contacted for guaranteed values.
OUTPUT CAPACITOR SELECTION FOR SW1 AND SW2
A ceramic output capacitor of 10 F, 6.3V is recommended
with an ESR of about 2m
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
COUT:
Estimated reactive output ripple
V
ROUT:
Estimated real output ripple
V
PPOUT:
Estimated peak-to-peak output ripple
The output capacitor needs to be mounted as close as pos-
sible to the output pin of the device. For better temperature
performance, X7R or X5R types are recommended. DC bias
characteristics of ceramic capacitors must be considered
when selecting case sizes like 0805 and 0603.
DC bias characteristics vary from manufacturer to manufac-
turer and by case size. DC bias curves should be requested
from them as part of the capacitor selection process. ESR is
typically higher for smaller packages.
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
COUT). ESRCOUT is frequency depen-
dent as well as temperature dependent. The R
ESR should be
calculated with the applicable switching frequency and ambi-
ent temperature.
www.national.com
22
LM26480
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參數(shù)描述
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LM26480SQX-BF 制造商:NSC 制造商全稱(chēng):National Semiconductor 功能描述:Externally Programmable Dual High-Current Step-Down DC/DC and Dual Linear Regulators
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