13

LTC1563-2/LTC1563-3

156323fa

Figure 5. 4th Order Filter Connections (Power Supply, Ground,

EN and LP Connections Not Shown for Clarity). Table 1 Shows

Resistor Values

1

2

3

4

5

6

7

8

16

15

14

13

12

11

10

9

LP

SA

NC

INVA

NC

LPA

AGND

LPB

NC

INVB

NC

SB

NC

EN

LTC1563-2

1563 F05

R31

R32

R22

R21

R11

R12

4th Order Filter Responses Using the LTC1563-2

FREQUENCY (Hz)

0.1

–20

–40

–60

–80

–90

10

0

10

1

1563 F05a

BUTTERWORTH

0.5dB RIPPLE

CHEBYSHEV

0.1dB RIPPLE

CHEBYSHEV

Figure 5a. Frequency Response

FREQUENCY (Hz)

0.1

–2

–4

–6

–8

–10

1

0

2

1

1563 F05b

BUTTERWORTH

0.5dB RIPPLE

CHEBYSHEV

0.1dB RIPPLE

CHEBYSHEV

Figure 5b. Passband Frequency Response

TIME (s)

0

1.2

1.0

0.8

0.6

0.4

0.2

0

1.0

0.5

1.5

2.0

1563 F05c

2.5

3.0

BUTTERWORTH

0.5dB RIPPLE

CHEBYSHEV

0.1dB RIPPLE

CHEBYSHEV

Figure 5c. Step Response

Gain, of the 4th Order LTC1563-2 Lowpass Filter, Is Set to Unity. (Note 1)

0.1dB RIPPLE

0.5dB RIPPLE

BUTTERWORTH

CHEBYSHEV

CHEBYSHEV

25.6kHz

15kHz

13kHz

256kHz

135kHz

113kHz

R11 = R21 =

R31 =

R12 = R22 =

R32 =

Example: In HS mode, 0.1dB ripple Chebyshev, 100kHz cutoff frequency, R11 = R21 = 35k

≅ 34.8k (1%),

R31 = 27.39k

≅ 27.4k (1%), R12 = R22 = 256k ≅ 255k (1%), R32 = 17.43k ≅ 17.4k (1%)

Note 1: The resistor values listed in this table provide good approximations of the listed transfer functions. For the

optimal resistor values, higher gain or other transfer functions, use FilterCAD Version 3.0 (or newer) or contact the

Linear Technology Filter Applications group for assistance.