LTC1066-1

16

10661fa

1066-1 TA05

7.5V

–7.5V

7.5V

2ND ORDER BUTTERWORTH ANTI-

ALIASING FILTER PROVIDES –68dB

ATTENUATION TO INPUTS AT 2fCLK

–7.5V

VOUT

VIN

fCLK

CF

RF

1

2

3

4

5

6

7

8

9

18

17

16

15

14

13

12

11

10

C2

OUT A

–IN A

+IN A

V–

V+

CONNECT 1

FILTEROUT

50/100

CLK

V+

OUT B

+IN B

GND

FILTERIN

COMP 2

CONNECT 2

COMP 1

V–

0.1

µF

0.1

µF

0.1

µF

LTC1066-1

20

Ω

20

Ω

R1

R2

0.1

µF

C1

fCUTOFF =

,

=

fCLK

50

fCUTOFF

250

1

2

πRFCF

= 2Hz, SET RF = 80.6k, CF = 1µF AND C1 = 0.0027µF

1

2

πRFCF

f–3dB = 2•fCUTOFF (f–3dB IS THE –3dB FREQUENCY OF THE

2ND ORDER ANTI-ALIASING FILTER)

1

2

π(R1 + R2)C1

= 0.707•f–3dB, R2 = 17.946•R1, C2 = 10•C1

FOR CUTOFF FREQUENCIES 2kHz TO 5kHz, SET RF = 20k,

CF = 1µF AND R1 + R2 ≤ 2k

FOR CUTOFF FREQUENCIES <2kHz, SET R1 + R2 = RF

FOR EXAMPLE:

IF THE CUTOFF FREQUENCY OF LTC1066-1 IS 500Hz, THEN

f–3dB = 1000Hz

R1 + R2 = 80.6k, R1 = 4.22k AND R2 = 76.8k ROUNDED TO NEAREST 1% VALUE.

C2 = 0.027

µF ROUNDED TO NEAREST STANDARD VALUE.

NOTE: RF SHOULD BE ≤100k TO MINIMIZE DC OFFSET TO ±5.5mV

DC Accurate Lowpass Filter with Input Anti-Aliasing

(fCLK ≤ 250kHz)

TYPICAL APPLICATIO