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LTC1064-1

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

Linear Technology 

LTC1064-1

Low Noise, 8th Order, Clock

Sweepable Elliptic Lowpass Filter

FEATURES

■ 8th Order Filter in a 14-Pin Package

■ No External Components

■ 100:1 Clock to Center Ratio

■ 150µVRMS Total Wideband Noise

■ 0.03% THD or Better

■ 50kHz Maximum Corner Frequency

■ Operates from ±2.37V to ±8V Power Supplies

■ Passband Ripple Guaranteed Over Full Military

Temperature Range

U

APPLICATIO S

■ Antialiasing Filters

■ Telecom PCM Filters

DESCRIPTIO

The LTC®1064-1 is an 8th order, clock sweepable elliptic

(Cauer) lowpass switched capacitor filter. The passband

ripple is typically ±0.15dB, and the stopband attenuation

at 1.5 times the cutoff frequency is 68dB or more.

An external TTL or CMOS clock programs the value of the

filter’s cutoff frequency. The clock to cutoff frequency ratio

is 100:1.

No external components are needed for cutoff frequencies

up to 20kHz. For cutoff frequencies over 20kHz two low

value capacitors are required to maintain passband flatness.

The LTC1064-1 features low wideband noise and low

harmonic distortion even for input voltages up to 3VRMS.

In fact the LTC1064-1 overall performance completes with

equivalent multiple op amp RC active realizations.

The LTC1064-1 is available in a 14-pin DIP or 16-pin

surface mounted SW package.

The LTC1064-1 is pin compatible with the LTC1064-2.

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

TYPICAL APPLICATIO

VIN

8V

0.1µF

8th Order Clock Sweepable Lowpass

Elliptic Antialiasing Filter

1

14

INV C R(h, I)

2

VIN

13

COMP2*

3

AGND

V– 12

4

LTC1064-1

V+

fCLK

11 CLOCK

(TTL, ≤5MHz)

5

10

AGND

NC

6

COMP1*

7

INV A

9

VOUT

NC 8

VOUT

–8V

0.1µF

1064 TA01

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

CAPACITOR CLOSE TO THE PACKAGE.

FOR SERVO OFFSET NULLING APPLICATIONS, PIN 1 IS THE 2ND

STAGE SUMMING JUNCTION.

*FOR CUTOFF FREQUENCY ABOVE 20kHz, USE COMPENSATION

CAPACITORS (5pF TO 56pF) BETWEEN PIN 13 AND PIN 1

AND PIN 6 AND PIN 7.

Frequency Response

15

0

–15

–30

–45

–60

–75

–90

–105

0

5 10 15 20 25 30 35 40

FREQUENCY (kHz)

1064 TA02

8th ORDER CLOCK SWEEPABLE LOWPASS ELLIPTIC ANTIALIASING

FILTER MAINTAINS, FOR 0.1Hz ≤ fCUTOFF ≤ 10kHz, A ±0.15dB PASSBAND

RIPPLE AND 72dB STOPBAND ATTENUATION AT 1.5 × fCUTOFF.

TOTAL WIDEBAND NOISE = 150µVRMS, THD = 0.03% FOR VIN = 1VRMS

10641fa

1

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