APL1541 Просмотр технического описания (PDF) - Anpec Electronics

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APL1541

1A Low Dropout Fast Response Positive Adjustable Regulator and Fixed 3.3V

Anpec Electronics 

APL1541

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.

PD = (VIN - VOUT) x IOUT

Maximum junction temperature is equal to :

TJUNCTION = TAMBIENT + (PD x θJA)

Note: TJUNCTION must not exceed 125°C

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 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 ).

Thermal Considerations

APL1541 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. The thermal resistance for each ap-

plication will be affected by thermal interactions with

other components on the board. Some experimenta-

tion will be necessary to determine the actual value.

The power dissipation of APL1541 is equal to :

Copyright  ANPEC Electronics Corp.

9

Rev. A.2 - Oct., 2003

www.anpec.com.tw

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