APL1117-18FC-TR ANPEC [Anpec Electronics Coropration], APL1117-18FC-TR Datasheet - Page 10

• Manufacturer Part Number: APL1117-18FC-TR
• Description: 1A Low Dropout Fast Response Positive Adjustable Regulator and Fixed 1.8V, 2.5V, 2.85V and 3.3V
• Manufacturer: ANPEC [Anpec Electronics Coropration]

APL1117
Application Information (Cont.)
Output Capacitor (Cont.)
Aluminum electrolytics can also be used, as long as
the ESR of the capacitor is <1 . The value of the
output capacitor can be increased without limit. Higher
capacitance values help to improve transient response
and ripple rejection and reduce output noise.
The curves for Ripple Rejection were generated us-
ing an adjustable device with the adjust pin bypassed.
With a 22 F bypassing capacitor 75dB ripple rejec-
tion is obtainable at any output level. The impedance
of the adjust pin capacitor, at the ripple frequency,
should be < R1. R1 is normally in the range of 100 -
200 . The size of the required adjust pin capacitor
is a function of the input ripple frequency. At 120Hz,
with R1=100 , the adjust pin capacitor should be
13 F. For fixed voltage devices, and adjustable de-
vices without an adjust pin capacitor, the output ripple
will increase as the ratio of the output voltage to the
reference voltage (V
Thermal Considerations
APL1117 has thermal protection which limits junction
temperature to 150°C. However, device functionality
is only guaranteed to a maximum junction tempera-
ture of +125°C.
Both the TO-220, TO-252, TO-263 and SOT-223
packages use a copper plane on the PCB and the
PCB itself as a heatsink. To optimize the heat sinking
ability of the plane and PCB, solder the tab of the
package to the plane.
Copyright
Rev. B.8 - Jun., 2003
Ripple Rejection
ANPEC Electronics Corp.
OUT
/V
REF
).
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Figure 3&4 shows for the TO-252 and SOT-223 the
measured values of (J-A) for different copper area
sizes using a 2 layers, 1.6mm, and 6Sq. cm FR-4
PCB with 2oz. copper and a ground plane layer on
the backside area used for heatsinking. It can be
used as a rough guideline in estimating thermal
resistance.
(J-A) vs. copper area for the SOT-252 package
50
45
40
35
30
25
0
2
Top Copper Area (cm
4
Figure 3.
6
8
www.anpec.com.tw
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TA=25°C
2
)
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