LTC1064-4_15 Datasheet, PDF (1/12 Pages) Linear Technology – Low Noise, 8th Order, Clock Sweepable Cauer Lowpass Filter

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, f_CLK 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 f_CLK to f_CUTOFF 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 × f_CUTOFF. Cutoff frequencies up to
100kHz can be achieved. With Pin 10 at V^–, the f_CLK 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 3V_RMS 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 LTCMOS^TM silicon gate process.
TYPICAL APPLICATIO
8th Order Clock Sweepable Lowpass Elliptic Filter
V_IN
8V
0.1µF
1
14
INV C R(h, I)
2
V_IN
COMP2* ¹³
3
AGND
V^{– 12}
4
LTC1064-4
V⁺
f_CLK
11 _CLOCK
(TTL, ≤5MHz)
5
AGND
50/100 ¹⁰ _V⁺_/V^–
6
COMP1*
7
INV A
9
V_OUT
8
NC
V_OUT
–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
T_A = 25°C
0
f_CLK = 5MHz, 50:1
C_COMP1 = 30pF, C_COMP2 = 18pF
–20
–40
–60
f_CLK = 2MHz, 50:1
–80
f_CLK = 1MHz, 100:1
–100
1k
10k
100k
FREQUENCY (Hz)
1M
1064-4 TA01b
10644fb
1