LT1568

1

1568f

The LT

block with rail-to-rail inputs and outputs. The internal ca-

pacitors of the IC and the GBW product of the internal low

noise op amps are trimmed such that consistent and repeat-

able filter responses can be achieved. With a single resis-

tor value, the LT1568 provides a pair of matched 2-pole

Butterworth lowpass filters with unity gain suitable for I/Q

channels.

By using unequal-valued external resistors, the two 2-pole

sections can create different frequency responses or

gains. In addition, the two stages may be cascaded to

create a single 4-pole filter with a programmable re-

sponse. Capable of cutoff frequencies up to 10MHz, the

LT1568 is ideal for antialiasing or channel filtering in high

speed data communications systems. The LT1568 can

also be used as a bandpass filter.

The LT1568 features very low noise, supporting signal-to-

noise ratios of over 90dB. It also provides single-ended to

differential signal conversion for directly driving high

speed A/D converters. The LT1568 has a shutdown mode

that reduces supply current to approximately 0.5mA on a

5V supply.

The LT1568 is available in a narrow 16-lead SSOP

package.

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

s

Up to 10MHz Center Frequency on a Single 3V

Supply

s

Easy to Use—A Single Resistor Value Sets Lowpass

Cutoff Frequency (200kHz

Resistor Values Extend Cutoff Frequency Up to

10MHz

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Extremely Flexible—Different Resistor Values

Allow Lowpass Transfer Functions with or Without

Gain (Butterworth, Chebyshev or Custom)

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SNR = 92dB (

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THD = –84dB (

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Internal Capacitors Trimmed to

±0.75%

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Single 4-Pole Lowpass Filter or Matched Pair of

2-Pole Lowpass Filters

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Can be Connected as a Bandpass Filter

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Single-Ended or Differential Output

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Operates from Single 3V (2.7V Min) to

±5V Supply

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Rail-to-Rail Input and Output Voltages

Very Low Noise,

High Frequency Active RC,

Filter Building Block

s

Replaces Discrete RC Active Filters and LC Filter

Modules

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Antialiasing/Reconstruction Filters

s

Dual or I-and-Q Channels (Two Matched 2nd Order

Filters in One Package)

s

Single-Ended to Differential Conversion

s

Video Signal Processing

INVA

SA

OUTA

OUTA

GNDA

NC

INVB

SB

OUTB

OUTB

GNDB

EN

1

2

3

4

5

6

7

8

16

15

14

13

12

11

10

9

LT1568

511

Ω

0.1

µF

0.1

µF

511

Ω

511

Ω

511

Ω

511

Ω

1568 TA01

3V

THE PROPRIETARY ARCHITECTURE

ALLOWS FOR A SIMPLE RESISTOR

CALCULATION:

511

Ω

R = 128

10MHz

Amplitude and Phase Matched Dual Butterworth 2.5MHz Lowpass

Filter with Differential Output. Single 3V Supply Operation

FREQUENCY (Hz)

100k

–27

–21

–15

–9

–3

1M

10M

1568 TA02

3

–24

–18

–12

–6

0

Amplitude Response

DESCRIPTIO

FEATURES

APPLICATIO S

TYPICAL APPLICATIO