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LTC1064-4_09 Datasheet, PDF (1/12 Pages) Linear Technology – Low Noise, 8th Order, Clock Sweepable Cauer Lowpass Filter | |||
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LTC1064-4
Low Noise, 8th Order, Clock
Sweepable Cauer Lowpass Filter
FEATURES
â 8th Order Filter in a 14-Pin Package
â 80dB or More Stopband Attenuation at 2 Ã fCUTOFF
â 50:1, fCLK to fCUTOFF Ratio (Cauer)
100:1, fCLK to fâ3dB Ratio (Transitional)
â 135µVRMS Total Wideband Noise
â 0.03% THD or Better
â 100kHz Maximum fCUTOFF Frequency
â Operates up to ±8V Power Supplies
â Input Frequency Range up to 50 Times the Filter
Cutoff Frequency
U
APPLICATIO S
â Antialiasing Filters
â Telecom Filters
â 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 filterâs 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 Ã fCUTOFF. Cutoff frequencies up to
100kHz can be achieved. With Pin 10 at Vâ, the fCLK to
fâ3dB 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 Ã fâ3dB 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 Technologyâs
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
Vâ 12
4
LTC1064-4
V+
fCLK
11 CLOCK
(TTL, â¤5MHz)
5
AGND
50/100 10 V+/Vâ
6
COMP1*
7
INV A
9
VOUT
8
NC
VOUT
â8V
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
â20
â40
â60
fCLK = 2MHz, 50:1
â80
fCLK = 1MHz, 100:1
â100
1k
10k
100k
FREQUENCY (Hz)
1M
1064-4 TA01b
10644fb
1
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