TK71541AS データシートの表示（PDF） - Toko America Inc

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TK71541AS

LOW DROPOUT VOLTAGE REGULATOR

Toko America Inc  

APPLICATION INFORMATION (CONT)

TK715xxAS

INPUT-OUTPUT CAPACITORS (CONT)

OUTPUT NOISE IMPROVEMENT

An RC filter can be added to the output stage of the regulator to reduce output noise when the input voltage is high and

the output current only makes small changes. Select a regulator with a slightly higher output voltage because the final

output voltage will be reduced by the RC filter. If the output current does make a large change, the output voltage will

change. The following table shows output noise, and output voltage for various values of ROUT and COUT using a 3.5 V

device.

VIN = 4.0 V, CIN = 10 mF (aluminum electrolytic), COUT = (see table), ROUT = (see table)

VIN

VOUT ROUT

TK715xxA

CL = 2.2 µF

COUT

LOAD ADJ.

IOUT = 20, 30, 40 mA

MEASUREMENT CONDITION

IOUT

IOUT = 20 - 40 mA

20 mA

ROUT

0

10 W

VOUT

3.500 V

3.296 V

30 mA

6.8 W

3.287 V

40 mA

5.1 W

3.266 V

OUTPUT SIDE CAPACITOR (COUT)

10 µF

47 µF

100 µF

210 µV

150 µV

130 µV

76 µV

50 µV

40 µV

88 µV

55 µV

48 µV

100 µV

60 µV

48 µV

UNITS

µF

RMS

RMS

RMS

RMS

COUT

NOISE

RIPPLE REJECTION RATIO

An RC filter can be added to the input stage of the regulator to increase the ripple rejection when the input voltage is high.

Even if the resulting difference between VIN at the regulator (after the RC filter) and VOUT is small the TK71533AS will

output a stable voltage. The voltage dropped across the RC filter depends on the value of the input ripple noise. Select

the value of RIN such that the lowest value of VIN plus the ripple noise after the RC filter (peak to peak) is the output voltage

plus 0.2 V.

RIN

VIN

VOUT

TK715xxA

CIN

CL

LOAD ADJ.

IOUT = 20, 30, 40 mA

March 2001 TOKO, Inc.

Page 11

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