APL1117-GC-TU データシートの表示（PDF） - Anpec Electronics

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APL1117-GC-TU

1A Low Dropout Fast Response Positive Adjustable Regulator and Fixed 1.8V, 2.5V, 2.85V and 3.3V

Anpec Electronics 

APL1117

Application Information (Cont.)

Output Capacitor (Cont.)

Aluminum electrolytics can also be used, as long as

the ESR of the capacitor is <1Ω. 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.

Ripple Rejection

The curves for Ripple Rejection were generated us-

ing an adjustable device with the adjust pin bypassed.

With a 22µF 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 100Ω-

200Ω. The size of the required adjust pin capacitor

is a function of the input ripple frequency. At 120Hz,

with R1=100Ω, the adjust pin capacitor should be

13µF. 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 (VOUT /VREF ).

Figure 3&4 shows for the TO-252 and SOT-223 the

measured values of 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.

50

TA=25°C

45

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 SOT-252 package

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  ANPEC Electronics Corp.

10

Rev. B.8 - Jun., 2003

www.anpec.com.tw

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