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LTC1064-4C

Low Noise, 8th Order, Clock Sweepable Cauer Lowpass Filter

Linear Technology 

LTC1064-4

Low Noise, 8th Order, Clock

Sweepable Cauer Lowpass Filter

FEATURES

■ 8th Order Filter in a 14-Pin Package

■ 80dB or More Stopband Attenuation at 2 × fCUTOFF

■ 50:1, fCLK to fCUTOFF Ratio (Cauer)

100:1, fCLK to f–3dB Ratio (Transitional)

■ 135µVRMS Total Wideband Noise

■ 0.03% THD or Better

■ 100kHz Maximum fCUTOFF Frequency

■ Operates up to ±8V Power Supplies

■ Input Frequency Range up to 50 Times the Filter

Cutoff Frequency

U

APPLICATIO S

■ Antialiasing Filters

■ Telecom Filters

■ Sinewave Generators

, LTC and LT are registered trademarks of Linear Technology Corporation.

LTCMOS is a trademark of Linear Technology Corporation.

DESCRIPTIO

The LTC®1064-4 is an 8th order, clock sweepable Cauer

lowpass switched capacitor filter. An external TTL or

CMOS clock programs the value of the filter’s cutoff

frequency. With Pin 10 at V+, the fCLK to fCUTOFF ratio is

50:1; the filter has a Cauer response and with compensa-

tion the passband ripple is ±0.1dB. The stopband attenu-

ation is 80dB at 2 × fCUTOFF. Cutoff frequencies up to

100kHz can be achieved. With Pin 10 at V–, the fCLK to

f–3dB ratio is 100:1, the filter has a transitional Butterworth-

Cauer response with lower noise and lower delay

nonlinearity than the Cauer response. The stopband

attenuation at 2.5 × f–3dB is 92dB. Cutoff frequencies up to

50kHz can be achieved.

The LTC1064-4 features low noise and low harmonic

distortion even when input voltages up to 3VRMS are

applied. The LTC1064-4 overall performance competes

with equivalent multiple op amp active realizations. The

LTC1064-4 is pin compatible with the LTC1064-1,

LTC1064-2 and LTC1064-3.

The LTC1064-4 is manufactured using Linear Technology’s

enhanced LTCMOSTM silicon gate process.

TYPICAL APPLICATIO

8th Order Clock Sweepable Lowpass Elliptic Filter

VIN

8V

0.1µF

1

14

INV C R(h, I)

2

VIN

COMP2* 13

3

AGND

V– 12

4

LTC1064-4

V+

fCLK

11 CLOCK

(TTL, ≤5MHz)

5

AGND

50/100 10 V+/V–

6

COMP1*

7

INV A

9

VOUT

8

NC

VOUT

–8V

0.1µF

1064 TA01

* FOR FREQUENCIES ABOVE 20kHz AND MINIMUM PASSBAND RIPPLE REFER

TO THE PIN DESCRIPTION SECTION FOR COMPENSATION GUIDELINES.

NOTE:THE POWER SUPPLIES SHOULD BE BYPASSED BY A 0.1µF CAPACITOR

CLOSE TO THE PACKAGE. BYPASSING PIN 10 WITH 0.1µF CAPACITOR

REDUCES CLOCK FEEDTHROUGH. THE CONNECTION BETWEEN PINS 7

AND 14 SHOULD BE PHYSICALLY DONE UNDER THE PACKAGE.

Frequency Response

20

TA = 25°C

0

fCLK = 5MHz, 50:1

CCOMP1 = 30pF, CCOMP2 = 18pF

–20

–40

–60

fCLK = 2MHz, 50:1

–80

fCLK = 1MHz, 100:1

–100

1k

10k

100k

FREQUENCY (Hz)

1M

1064-4 TA01b

10644fb

1

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