LTC1064-1_15 Datasheet, PDF (1/8 Pages) Linear Technology – Low Noise, 8th Order, Clock Sweepable Elliptic Lowpass Filter

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 3V_RMS.
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
V_IN
8V
0.1µF
8th Order Clock Sweepable Lowpass
Elliptic Antialiasing Filter
1
14
INV C R(h, I)
2
V_IN
13
COMP2*
3
AGND
V^{– 12}
4
LTC1064-1
V⁺
f_CLK
11 _CLOCK
(TTL, ≤5MHz)
5
10
AGND
NC
6
COMP1*
7
INV A
9
V_OUT
NC ⁸
V_OUT
–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 ≤ f_CUTOFF ≤ 10kHz, A ±0.15dB PASSBAND
RIPPLE AND 72dB STOPBAND ATTENUATION AT 1.5 × f_CUTOFF.
TOTAL WIDEBAND NOISE = 150µV_RMS, THD = 0.03% FOR V_IN = 1V_RMS
10641fa
1