APL1117-18 データシートの表示（PDF） - Anpec Electronics
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APL1117-18
Anpec Electronics
APL1117-18 Datasheet PDF : 19 Pages
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APL1117
Application Information (Cont.)
Ripple Rejection
The curves for Ripple Rejection were generated using an
adjustable device with the adjust pin bypassed. With a
22µF bypassing capacitor, 75dB ripple rejection is ob-
tainable 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 100Ω to 200Ω. The size of the
required adjust pin capacitor is the function of the input
ripple frequency. At 120Hz, with R1=100Ω, the adjust pin
capacitor should be 13µF. For fixed voltage devices and
adjustable devices without an adjust pin capacitor, the
output ripple will increase as the ratio of the output volt-
age to the reference voltage (VOUT /VREF ).
Thermal Consideration
The APL1117 regulators have thermal protection to limit
junction temperature to 150ºC. However, the device is
recommended to be operated under 125ºC.
A heatsink may be required depending on the maximum
power dissipation and maximum ambient temperature
of the application. Figure 3&4 show for the TO-252-3 and
SOT-223 the measured values θ(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. Both
the TO-252-3 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.
50
TA=25oC
45
60
TA=25oC
55
50
45
40
35
30
0 2 4 6 8 10 12 14
Top Copper Area (cm2)
Figure 4. θ(J-A) vs. copper area for the SOT-223 package
The thermal resistance for each application will be af-
fected by thermal interactions with other components on
the board. Some experimentation will be necessary to
determine the actual value.
The power dissipation of APL1117 is equal to:
PD = (VIN - VOUT) x IOUT
Maximum junction temperature is equal to:
T (Note)
JUNCTION
=
TAMBIENT
+
(PD
x
θJA)
Note: TJUNCTION must not exceed 125°C
Safe Operation Area
Using the experiment result of previous Thermal Con-
sideration (choose the one with 1.5cmx1.5cm polygen
area) and θ(J-A)=50°C/W spec, the safe operation area of
APL1117 in TO-252-3 and SOT-223 packages can be ob-
tained as Figure 5.
1200
1000
TA=25oC
800
40
35
30
25
0 2 4 6 8 10 12 14
Top Copper Area (cm2)
Figure 3. θ(J-A) vs. copper area for the TO-252-3 package
600
TA=55oC
400
TA=85oC
200
0
0.851 1.31.45 1.75 2.05 2.35 2.65 2.953.1
Input-Output Voltage Differential (V)
Figure 5. Safe Operation Area of APL1117 in TO-252-3
and SOT-223 packages (limited by Power Dissipation with
T
< 125°C)
JUNCTION
Copyright © ANPEC Electronics Corp.
10
Rev. C.10 - Sep., 2010
www.anpec.com.tw
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