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LTC1164-6 Low Power 8th Order Pin Selectable Elliptic or Linear Phase Lowpass Filter
FEATURES
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DESCRIPTIO
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8th Order Pin Selectable Elliptic or Bessel Filter in a 14-Pin Package 4mA Supply Current with 5V Supplies 64dB Attenuation at 1.44 fCUTOFF (Elliptic Response) fCUTOFF up to 30kHz (50:1 fCLK to fCUTOFF Ratio) 110VRMS Wideband Noise with 5V Supplies Operates at Single 5V Supply with 1VRMS Input Range Operates up to 8V Supplies TTL/CMOS Compatible Clock Input No External Components
The LTC1164-6 is a monolithic 8th order elliptic lowpass filter featuring clock-tunable cutoff frequency and low power supply current. Low power operation is achieved without compromising noise or distortion performance. At 5V supplies the LTC1164-6 uses only 4mA supply current while keeping wideband noise below 110VRMS. With a single 5V supply, the LTC1164-6 can provide up to 10kHz cutoff frequency and 80dB signal-to-noise ratio while consuming only 2.5mA. The LTC1164-6 provides an elliptic lowpass rolloff with stopband attenuation of 64dB at 1.44 fCUTOFF and an fCLKto-fCUTOFF ratio of 100:1 (pin 10 to V -). For a ratio of 100:1, fCUTOFF can be clock-tuned up to 10kHz. For a fCLK-tofCUTOFF ratio of 50:1 (pin 10 to V +), the LTC1164-6 provides an elliptic lowpass filter with fCUTOFF frequencies up to 20kHz. When pin 10 is connected to ground, the LTC1164-6 approximates an 8th order linear phase response with 65dB attenuation at 4.5 f - 3dB and fCLK / f - 3dB ratio of 160:1. The LTC1164-6 is pin compatible with the LTC1064-1.
APPLICATI
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S
Anti-Aliasing Filters Battery-Operated Instruments Telecommunication Filters
TYPICAL APPLICATI
10kHz Anti-Aliasing Elliptic Filter
NC VIN 1 2 3 8V 4 5 6 7 LTC1164-6 14 13 12 11 10 9 8
1164-6 TA01
0
NC -8V CLK = 1MHz -8V VOUT GAIN (dB)
-10 -20 -30 -40 -50 -60 -70
WIDEBAND NOISE = 115VRMS NOTE: THE CONNECTION FROM PIN 7 TO PIN 14 SHOULD BE MADE UNDER THE PACKAGE. THE POWER SUPPLIES SHOULD BE BYPASSED BY A 0.1F CAPACITOR AS CLOSE TO THE PACKAGE AS POSSIBLE.
-80 1 10 FREQUENCY (kHz) 100
1164-6 TA02
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Frequency Response
UO
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1
LTC1164-6 ABSOLUTE AXI U RATI GS (Note 1)
Operating Temperature Range LTC1164-6C ...................................... - 40C to 85C LTC1164-6M ................................... - 55C to 125C Storage Temperature Range ................ - 65C to 150C Lead Temperature (Soldering, 10 sec)................. 300C Total Supply Voltage (V + to V -) ............................. 16V Input Voltage (Note 2) ......... (V ++ 0.3V) to (V - - 0.3V) Output Short-Circuit Duration ......................... Indefinite Power Dissipation............................................. 400mW Burn-In Voltage ...................................................... 16V
PACKAGE/ORDER I FOR ATIO
TOP VIEW NC VIN GND V+ GND LP6 CONNECT 1 1 2 3 4 5 6 7 14 CONNECT 2 13 NC 12 V-
ORDER PART NUMBER LTC1164-6CN LTC1164-6CJ LTC1164-6MJ
11 CLK 10 ELL/BESS 9 8 VOUT NC
J PACKAGE 14-LEAD CERAMIC DIP
N PACKAGE 14-LEAD PLASTIC DIP
TJMAX = 150C, JA = 65C/W (J) TJMAX = 110C, JA = 65C/W (N)
ELECTRICAL CHARACTERISTICS
PARAMETER Passband Gain 0.1Hz to 0.25 fCUTOFF (Note 4) Passband Ripple with VS = Single 5V Gain at 0.50 fCUTOFF (Note 3) Gain at 0.90 fCUTOFF (Note 3) Gain at 0.95 fCUTOFF (Note 3) Gain at fCUTOFF (Note 3) Gain at 1.44 fCUTOFF (Note 3) Gain at 2.0 fCUTOFF (Note 3) Gain with fCLK = 20kHz Gain with VS = 2.375V Input Frequency Range (Tables 3, 4) Maximum fCLK (Table 3)
VS = 7.5V, RL = 10k, TA = 25C, fCLK = 400kHz, TTL or CMOS level (maximum clock rise or fall time 1s) and all gain measurements are referenced to passband gain, unless otherwise specified. (fCLK /fCUTOFF) = 4kHz at 100:1 and 8kHz at 50:1.
CONDITIONS fIN = 1kHz, (fCLK / fC) = 100:1 1Hz to 0.8 fC (Table 2) fIN = 2kHz, (fCLK / fC) = 100:1 fIN = 3.6kHz, (fCLK / fC) = 100:1 fIN = 3.8kHz, (fCLK / fC) = 100:1 fIN = 4kHz, (fCLK / fC) = 100:1 fIN = 8kHz, (fCLK / fC) = 50:1 fIN = 5.76kHz, (fCLK / fC) = 100:1 fIN = 8kHz, (fCLK / fC) = 100:1 fIN = 200Hz, (fCLK / fC) = 100:1 fIN = 400kHz, fIN = 2kHz, (fCLK / fC) = 100:1 fIN = 400kHz, fIN = 4kHz, (fCLK / fC) = 100:1 (fCLK / fC) = 100:1 (fCLK / fC) = 50:1 VS 7.5V VS 5V VS = Single 5V, AGND = 2V
q q q q q q q q
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TOP VIEW NC 1 VIN 2 GND 3 V+ 4 16 CONNECT 2 15 NC 14 V - 13 NC 12 CLK 11 ELL/BESS 10 NC 9 S PACKAGE 16-LEAD PLASTIC SOL
TJMAX = 110C, JA = 85C/W
ORDER PART NUMBER LTC1164-6CS
GND 5 NC 6 LP6 7 CONNECT 1 8
VOUT
MIN - 0.50 - 0.45 - 0.75 -1.40 - 3.50 - 3.00 -69 - 69 - 3.50 - 0.50 - 3.30
TYP - 0.15 0.1 to - 0.3 - 0.10 - 0.30 - 0.70 - 2.70 - 2.10 - 64 - 64 - 2.70 - 0.10 - 2.50 0 - MAX 0.25 0.10 0.10 - 0.40 - 2.30 - 1.50 - 58 - 58 - 2.30 0.30 - 2.00
UNITS dB dB dB dB dB dB dB dB dB dB dB dB kHz kHz MHz MHz MHz
LTC1164-6
VS = 7.5V, RL = 10k, TA = 25C, fCLK = 400kHz, TTL or CMOS level (maximum clock rise or fall time 1s) and all gain measurements are referenced to passband gain, unless otherwise specified. (fCLK / fCUTOFF) = 4kHz at 100:1 and 8kHz at 50:1.
PARAMETER Clock Feedthrough CONDITIONS Input at GND, f = fCLK, Square Wave VS = 7.5V, (fCLK / fC) = 100:1 VS = 5V, (fCLK / fC) = 50:1 Input at GND, 1Hz f < fCLK VS = 7.5V VS = 2.5V VS = 2.375V VS = 5V VS = 7.5V VS = 5V, (fCLK / fC) = 100:1 VS = 5V, (fCLK / fC) = 100:1 VS = 2.375V, TA > 25C VS = 5V, TA > 25C
q q q q
ELECTRICAL CHARACTERISTICS
MIN
TYP 500 200 115 5% 100 5% 40 1.50 4.10 5.90 100 100 2.5 4.5 7.0
MAX
UNITS VRMS VRMS VRMS VRMS k V V V mV V/C mA mA mA mA mA mA V
Wideband Noise
Input Impedance Output DC Voltage Swing
30 1.25 3.70 5.40
70
Output DC Offset Output DC Offset TempCo Power Supply Current
160 4.0 4.5 7.0 8.0 11.0 12.5 8
q
VS = 7.5V, TA > 25C
q
Power Supply Range The q denotes specifications which apply over the full operating temperature range. Note 1: Absolute Maximum Ratings are those values beyond which life of the device may be impaired. Note 2: Connecting any pin to voltages greater than V + or less than V -
2.375
may cause latch-up. It is recommended that no sources operating from external supplies be applied prior to power-up of the LTC1164-6. Note 3: All gains are measured relative to passband gain. Note 4: The cutoff frequency of the filter is abbreviated as fCUTOFF or fC.
TYPICAL PERFOR A CE CHARACTERISTICS
Stopband Gain vs Frequency (Elliptic Response)
10 0 -10 -20
GAIN (dB)
GAIN (dB)
-30 -40 -50 -60 -70 -80 -90 2 4 6
8 10 12 14 16 18 20 22 FREQUENCY (kHz)
1164-6 G01
UW
Stopband Gain vs Frequency (Elliptic Response)
10 0 -10 -20 -30 -40 -50 -60 -70 -80 -90 2 4 6 8 10 12 14 16 18 20 22 FREQUENCY (kHz)
1164-6 G02
VS = 5V fCLK = 500kHz fC = 5kHz (fCLK /fC) = 100:1 (PIN 10 AT V - ) TA = 25C
VS = 5V fCLK = 250kHz (fCLK /fC) = 50:1 (PIN 10 AT V +) TA = 25C WITH EXTERNAL SINGLE POLE LOWPASS RC FILTER (f - 3dB = 10kHz)
3
LTC1164-6
TYPICAL PERFOR A CE CHARACTERISTICS
Stopband Gain vs Frequency (Linear Phase Response)
10 0 -10 -20
GAIN (dB)
GAIN (dB)
-30 -40 -50 -60 -70 -80 -90 2 6
10 14 18 22 26 30 34 38 42 FREQUENCY (kHz)
1164-6 G03
Passband Gain vs Frequency
3
0.8 0.4 0 -0.4 GAIN (dB) -0.8 -1.2 -1.6 -2.0 -2.4 -2.8 0.4 VS = 5V fCLK = 500kHz fC = 5kHz (fCLK /fC) = 100:1 (PIN 10 AT V - ) TA = 25C (10 REPRESENTATIVE UNITS) 1.0 2.2 2.8 1.6 FREQUENCY (kHz) 3.4 4.0
GAIN (dB)
-2 -3 -4 -5 -6 -7 1 VS = 5V fCLK = 800kHz fC = 5kHz (fCLK /fC) = 160:1 (PIN 10 AT GND) TA = 25C
GAIN
GAIN (dB)
Passband vs Frequency and fCLK
2.0 1.5 1.0 0.5 VS = 5V (fCLK /fC) = 100:1 (PIN 10 AT V - ) TA = 25C A. fCLK = 400kHz f CUTOFF = 4kHz B. fCLK = 600kHz f CUTOFF = 6kHz C. fCLK = 800kHz f CUTOFF = 8kHz D. fCLK = 1MHz f CUTOFF = 10kHz
3 2 1 0 -1
GAIN (dB)
GAIN (dB)
0 - 0.5 -1.0 -1.5 -2.0 -2.5 - 3.0 1 A B C D
5 INPUT FREQUENCY (kHz)
4
UW
1164-6 G05
1164-6 G06
Passband Gain and Phase vs Frequency
A.RESPONSE WITHOUT EXTERNAL RC FILTER B.RESPONSE WITH AN EXTERNAL SINGLE POLE LOWPASS RC FILTER (f - 3dB AT 10kHz) 2.0 1.5 1.0 0.5 0 -0.5 -1.0 -1.5 -2.0 VS = 5V fCLK = 500kHz fC = 5kHz (fCLK /fC) = 100:1 (PIN 10 AT V - ) TA = 25C 1 4 2 3 FREQUENCY (kHz) 5
1164-6 G04
0 -45 -90 -135
PHASE (DEG)
VS = 5V fCLK = 800kHz fC = 5kHz (fCLK /fC) = 160:1 (PIN 10 AT GND) TA = 25C
-180 -225 -270 -315 -360 -405 -450
A B
-2.5 -3.0
Passband Gain and Phase vs Frequency (Linear Phase Response)
0 -30 -60 PHASE -90
Maximum Passband over Temperature
0.4 0.2 0 -0.2 -0.4 -0.6 -0.8 -1.0 -1.2 -1.4 -1.6 1 VS = 5V fCLK = 1MHz fC = 10kHz (fCLK /fC) = 100:1 (PIN 10 AT V - ) 5 FREQUENCY (kHz) 10
1164-6 G07
A B C A.T A = 125C B.T A = 85C D.T A = -40C
2 1 0 -1
PHASE (DEG)
-120 -150 -180 -210 -240 -270 -300 4 2 3 FREQUENCY (kHz) 5
1164-6 G11
Passband Gain and Phase vs Frequency and fCLK
0 -45 A B PHASE A B VS = 5V fCLK = 250kHz fC = 5kHz (fCLK /fC) = 50:1 (PIN 10 AT V - ) TA = 25C 1 2 3 4 FREQUENCY (kHz) 5
1164-6 G08
-90 -135 -180 -225 -270 -315 -360 -405 -450 -495 -540
-2 -3 -4 -5 -6 -7 -8 -9
A.RESPONSE WITHOUT EXTERNAL SINGLE POLE RC FILTER B.RESPONSE WITH AN EXTERNAL SINGLE POLE LOWPASS RC FILTER (f - 3dB AT 10kHz)
PHASE (DEG)
10
LTC1164-6
TYPICAL PERFOR A CE CHARACTERISTICS
Passband vs Frequency and fCLK
2.0 1.5 1.0 0.5 A. fCLK = 250kHz f CUTOFF = 5kHz B. fCLK = 500kHz f CUTOFF = 10kHz C. fCLK = 1MHz f CUTOFF = 20kHz
2.0 1.5 1.0 0.5 TA = 70C TA = -40C VS = SINGLE 5V (fCLK /fC) = 50:1 GND = 2V WITH EXTERNAL RC LOWPASS FILTER (f - 3dB = 40kHz) 2 4 6 8 10 12 14 16 18 20 22 FREQUENCY (kHz)
1164-6 G10
GAIN (dB)
-0.5 -1.0 -1.5 -2.0 -2.5 -3.0 1 VS = 8V (fCLK /f C) = 50:1 (PIN 10 AT V +) TA = 25C
GAIN (dB)
30
1164-6 G09
0 A B C
10 FREQUENCY (kHz)
Group Delay vs Frequency (Linear Phase Response)
250 fCLK = 800kHz (fCLK /fC) = 160:1 fC = 5kHz 700 600
200
GROUP DELAY (s)
GROUP DELAY (s)
150
B 400 300 200 100 VS = 5V fC = 5kHz TA = 25C 1 2 4 3 FREQUENCY (kHz) 5
1164-6 G12
THD + NOISE (dB)
100
50
0 1 2 3 45678 FREQUENCY (kHz) 9 10 11
1164-6 G22
THD + Noise vs Frequency (Elliptic Response)
- 40 -45 - 50 VS = 5V, VIN = 1VRMS, fCLK = 500kHz, fC = 10kHz, (fCLK /fC) = 50:1, TA = 25C, WITH EXTERNAL RC LOWPASS FILTER (f - 3dB = 20kHz) (5 REPRESENTATIVE UNITS) - 40 -45 - 50 THD + NOISE (dB) -55 -60 -65 -70 -75 -80 -85 1 5 FREQUENCY (kHz) 10
1164-6 G14
THD + NOISE (dB)
THD + NOISE (dB)
-55 -60 -65 -70 -75 -80 -85 -90
UW
Maximum Passband over Temperature
0 -0.5 -1.0 -1.5 -2.0 -2.5 -3.0
Group Delay vs Frequency (Elliptic Response)
- 40
A.f CLK = 250kHz, (fCLK /fC) = 50:1 WITH EXTERNAL RC LOWPASS FILTER (f C = 10kHz) B.f CLK = 500kHz (f CLK /fC) = 100:1
THD + Noise vs Frequency (Elliptic Response)
-45
A
- 50 -55 -60 -65 -70 -75 -80 -85 -90 1
500
VS = 5V, VIN = 1VRMS (20k RESISTOR PIN 14 TO V - ) fCLK = 500kHz, fC = 5kHz (fCLK /fC) = 100:1, TA = 25C (5 REPRESENTATIVE UNITS)
0
2 3 FREQUENCY (kHz)
4
1164-6 G13
5
THD + Noise vs Frequency (Elliptic Response)
-40
VS = SINGLE 5V, VIN = 0.7VRMS fCLK = 500kHz, fC = 5kHz, (fCLK /fC) = 100:1, TA = 25C (5 REPRESENTATIVE UNITS)
THD + Noise vs Frequency (Linear Phase Response)
-45 -50 -55 -60 -65 -70 -75 -80 -85 -90 VS = 5V VIN = 1VRMS fCLK = 800kHz fC = 5kHz (fCLK /fC) = 160:1 TA = 25C
-90 0.5
1 FREQUENCY (kHz)
5
1164-6 G16
1
2 3 FREQUENCY (kHz)
4
1164-6 G23
5
5
LTC1164-6
TYPICAL PERFOR A CE CHARACTERISTICS
THD + Noise vs RMS Input (Elliptic Response)
- 40 -45 - 50 THD + NOISE (dB) (fCLK /fC) = 100:1 OR 50:1 fIN = 1kHz, TA = 25C
THD + NOISE (dB)
-55 -60 -65 -70 -75 -80 -85 -90 0.1 1 INPUT (VRMS)
1164-6 G17
VS = 5V
-60 -65 -70 -75 -80 -85 A. GND = 2.5V B. GND = 2V 1 INPUT (VRMS)
1164-6 G18
CURRENT (mA)
VS = 7.5V
Transient Response
2V/DIV
2V/DIV
VS = 7.5V, VIN = 3V 100Hz SQUARE WAVE fCLK = 500kHz, (fCLK /f C) = 100:1, fCUTOFF = 5kHz ELLIPTIC RESPONSE
PI FU CTIO S
+ -
(14-Lead Dual-In-Line Package)
Power Supply Pins (4, 12) The V (pin 4) and the V (pin 12) should be bypassed with a 0.1F capacitor to an adequate analog ground. The filter's power supplies should be isolated from other digital or high voltage analog supplies. A low noise linear supply is recommended. Using a switching power supply will lower the signal-to-noise ratio of the filter. The supply during power-up should have a slew rate less than 1V/s. When V + is applied before V - and V - could go above ground, a signal diode must be used to clamp V -. Figures
6
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5
THD + Noise vs RMS Input for Single 5V (Elliptic Response)
-40 -45 -50 -55 A B (fCLK /fC) = 100:1 OR 50:1 fIN = 1kHz, TA = 25C
12 11 10 9 8 7 6 5 4 3 2 1 0
Power Supply Current vs Power Supply Voltage
-55C
25C 125C
-90 0.1
2
0
1
234 5678 POWER SUPPLY (V + OR V -)
9
10
1164-6 G19
Transient Response
1ms/DIV
1164-6 G20
1ms/DIV
1164-6 G21
VS = 7.5V, VIN = 3V 100Hz SQUARE WAVE fCLK = 800kHz, (fCLK /f C) = 160:1, fCUTOFF = 5kHz LINEAR PHASE RESPONSE
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1 and 2 show typical connections for dual and single supply operation. Clock Input Pin (11) Any TTL or CMOS clock source with a square-wave output and 50% duty cycle (10%) is an adequate clock source for the device. The power supply for the clock source should not be the filter's power supply. The analog ground for the filter should be connected to clock's ground at a single point only. Table 1 shows the clock's low and high
LTC1164-6
PI FU CTIO S
level threshold value for a dual or single supply operation. A pulse generator can be used as a clock source provided the high level ON time is greater than 0.5s. Sine waves are not recommended for clock input frequencies less than 100kHz, since excessively slow clock rise or fall times generate internal clock jitter (maximum clock rise or fall time 1s). The clock signal should be routed from the right side of the IC package to avoid coupling into any input or output analog signal path. A 1k resistor between clock source and pin 11 will slow down the rise and fall times of the clock to further reduce charge coupling, Figures 1 and 2.
V- 1 VIN V+ 2 3 4 5 0.1F 6 7 LTC1164-6 14 13 12 11 10 9 8 + GND DIGITAL SUPPLY 1k CLOCK SOURCE
* OPTIONAL
Figure 1. Dual Supply Operation for fCLK/fCUTOFF = 100:1
1 VIN V+ 0.1F 10k 2 3 4 5 6 7 LTC1164-6
10k
+
1F VOUT
1164-6 F02
Figure 2. Single Supply Operation for fCLK/fCUTOFF = 100:1 Table 1. Clock Source High and Low Threshold Levels
POWER SUPPLY Dual Supply = 7.5V Dual Supply = 5V Dual Supply = 2.5V Single Supply = 12V Single Supply = 5V HIGH LEVEL 2.18V 1.45V 0.73V 7.80V 1.45V LOW LEVEL 0.5V 0.5V - 2.0V 6.5V 0.5V
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(14-Lead Dual-In-Line Package)
Analog Ground Pins (3, 5) The filter performance depends on the quality of the analog signal ground. For either dual or single supply operation, an analog ground plane surrounding the package is recommended. The analog ground plane should be connected to any digital ground at a single point. For dual supply operation, pins 3 and 5 should be connected to the analog ground plane. For single supply operation pins 3 and 5 should be biased at 1/2 supply and they should be bypassed to the analog ground plane with at least a 1F capacitor (Figure 2). For single 5V operation at the highest fCLK of 1MHz, pins 3 and 5 should be biased at 2V. This minimizes passband gain and phase variations (see Typical Performance Characteristics curves: Maximum Passband for Single 5V, 50:1; and THD + Noise vs RMS Input for Single 5V, 50:1). Elliptic/Linear Phase Select Pin (10) The DC level at this pin selects the desired filter response, elliptic or linear phase and determines the ratio of the clock frequency to the cutoff frequency of the filter. Pin 10 connected to V - provides an elliptic lowpass filter with clock-to-fCUTOFF ratio of 100:1. Pin 10 connected to analog ground provides a linear phase lowpass filter with a clock- to-f -3dB ratio of 160:1 and a transient response overshoot of 1%. When pin 10 is connected to V + the clock-to-fCUTOFF ratio is 50:1 and the filter response is elliptic. Bypassing pin 10 to analog ground reduces the output DC offsets. If the DC level at pin 10 is switched mechanically or electrically at slew rates greater than 1V/ s while the device is operating, a 10k resistor should be connected between pin 10 and the DC source. Filter Input Pin (2) The input pin is connected internally through a 50k resistor tied to the inverting input of an op amp. Filter Output Pins (9, 6) Pin 9 is the specified output of the filter; it can typically source or sink 1mA. Driving coaxial cables or resistive loads less than 20k will degrade the total harmonic distortion of the filter. When evaluating the device's distortion an output buffer is required. A noninverting buffer, Figure 3,
*
0.1F
VOUT
1164-6 F01
14 13 12 11 10 9 8 + GND DIGITAL SUPPLY 1k CLOCK SOURCE
7
LTC1164-6
PI FU CTIO S (14-Lead Dual-In-Line Package)
can be used provided that its input common-mode range is well within the filter's output swing. Pin 6 is an intermediate filter output providing an unspecified 6th order lowpass filter. Pin 6 should not be loaded. External Connection Pins (7, 14) Pins 7 and 14 should be connected together. In a printed circuit board the connection should be done under the IC package through a short trace surrounded by the analog ground plane. NC Pin (1, 8, 13)
LT1006, fC < 5kHz LT1200, fC > 5kHz
1164-6 F03
Figure 3. Buffer for Filter Output
APPLICATI
S I FOR ATIO
Passband Response The passband response of the LTC1164-6 is optimized for a fCLK/fCUTOFF ratio of 100:1. Minimum passband ripple occurs from 1Hz to 80% of fCUTOFF. Athough the passband of the LTC1164-6 is optimized for ratio fCLK / fCUTOFF of 100:1, if a ratio of 50:1 is desired, connect a single pole lowpass RC (f -3dB = 2 fCUTOFF) at the output of the filter. The RC will make the passband gain response as flat as the 100:1 case. If the RC is omitted, and clock frequencies are below 500kHz the passband gain will peak by 0.4dB at 90% fCUTOFF.
Table 2. Typical Passband Ripple with Single 5V Supply (fCLK/fC) = 100:1, GND = 2V, 30kHz, Fixed Single Pole, Lowpass RC Filter at Pin 9 (See Typical Applications)
PASSBAND FREQUENCY PASSBAND GAIN (REFERENCED TO 0dB) fCUTOFF = 1kHz fCUTOFF = 10kHz TA = 0C TA = 25C TA = 70C TA = 25C (dB) (dB) (dB) (dB) 0.00 0.00 0.00 0.00 - 0.02 0.00 0.01 0.01 - 0.05 - 0.01 - 0.01 0.01 - 0.10 - 0.02 - 0.02 0.02 - 0.13 - 0.03 - 0.01 0.03 - 0.15 - 0.01 0.01 0.05 - 0.18 - 0.01 0.01 0.07 - 0.25 - 0.08 - 0.05 0.02 - 0.39 - 0.23 - 0.18 - 0.05 - 2.68 - 2.79 - 2.74 - 2.68
% of fCUTOFF 10 20 30 40 50 60 70 80 90 fCUTOFF
8
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1k
-
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Pins 1, 8, and 13 are not connected to any internal circuit point on the device and should preferably be tied to analog ground.
The gain peaking can approximate a sin / correction for some applications. (See Typical Performance Characteristics curve, Passband vs Frequency and fCLK at fCLK / fC = 50:1.) When the LTC1164-6 operates with a single 5V supply and its cutoff frequency is clock-tuned to 10kHz, an output single pole RC filter can also help maintain outstanding passband flatness from 0C to 70C. Table 2 shows details. Clock Feedthrough Clock feedthrough is defined as, the RMS value of the clock frequency and its harmonics that are present at the filter's output pin (9). The clock feedthrough is tested with the input pin (2) grounded and, it depends on PC board layout and on the value of the power supplies. With proper layout techniques the values of the clock feedthrough are shown in Table 3.
Table 3. Clock Feedthrough
VS 2.5V 5V 7.5V 50:1 60VRMS 100VRMS 150VRMS 100:1 60VRMS 200VRMS 500VRMS
Note: The clock feedthrough at 2.5V supplies is imbedded in the wideband noise of the filter. (The clock signal is a square wave.)
LTC1164-6
APPLICATI
S I FOR ATIO
Any parasitic switching transients during the rise and fall edges of the incoming clock are not part of the clock feedthrough specifications. Switching transients have frequency contents much higher than the applied clock; their amplitude strongly depends on scope probing techniques as well as grounding and power supply bypassing. The clock feedthrough, if bothersome, can be greatly reduced by adding a simple R/C lowpass network at the output of the filter pin (9). This R/C will completely eliminate any switching transient. Wideband Noise The wideband noise of the filter is the total RMS value of the device's noise spectral density and it is used to determine the operating signal-to-noise ratio. Most of its frequency contents lie within the filter passband and it cannot be reduced with post filtering. For instance, the LTC1164-6 wideband noise at 2.5V supply is 100VRMS, 90VRMS of which have frequency contents from DC up to the filter's cutoff frequency. The total wideband noise (VRMS) is nearly independent of the value of the clock. The clock feedthrough specifications are not part of the wideband noise. Speed Limitations The LTC1164-6 optimizes AC performance versus power consumption. To avoid op amp slew rate limiting at maximum clock frequencies, the signal amplitude should be kept below a specified level as shown on Table 4. Aliasing Aliasing is an inherent phenomenon of sampled data systems and it occurs when input frequencies close to the sampling frequency are applied. For the LTC1164-6 case, an input signal whose frequency is in the range of fCLK 4%, will be aliased back into the filter's passband. If, for instance, an LTC1164-6 operating with a 100kHz clock and 1kHz cutoff frequency receives a 98.5kHz, 10mVRMS input signal, a 1.5kHz, 10VRMS alias signal will appear at its output. When the LTC1164-6 operates with a clock-tocutoff frequency of 50:1, aliasing occurs at twice the clock frequency. Table 5 shows details.
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Table 4. Maximum VIN vs VS and fCLK
POWER SUPPLY 7.5V MAXIMUM fCLK 1.5MHz 1MHz 1MHz 1MHz 1MHz 1MHz 1MHz MAXIMUM VIN 1VRMS (fIN > 35kHz) 3VRMS (fIN > 25kHz) 0.7VRMS (fIN > 250kHz) 2.5VRMS (fIN > 25kHz) 0.5VRMS (fIN > 100kHz) 0.7VRMS (fIN > 25kHz) 0.5VRMS (fIN > 100kHz) 5V Single 5V
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Table 5. Aliasing (fCLK = 100kHz)
INPUT FREQUENCY OUTPUT LEVEL (Relative to Input) (VIN = 1VRMS) (kHz) (dB) fCLK/fC = 100:1, fCUTOFF = 1kHz 96 (or 104) 97 (or 103) 98 (or 102) 98.5 (or 101.5) 99 (or 101) 99.5 (or 100.5) fCLK/fC = 50:1, fCUTOFF = 2kHz 192 (or 208) 194 (or 206) 196 (or 204) 198 (or 202) 199 (or 201) 199.5(or 200.5) -75.0 - 68.0 - 65.0 - 60.0 - 3.2 - 0.5 - 76.0 - 68.0 - 63.0 - 3.4 - 1.3 - 0.9 OUTPUT FREQUENCY (Aliased Frequency) (kHz) 4.0 3.0 2.0 1.5 1.0 0.5 8.0 6.0 4.0 2.0 1.0 0.5
Table 6. Transient Response of LTC Lowpass Filters
DELAY TIME* (SEC) 0.50/fC 0.43/fC 0.43/fC 1.15/fC 1.20/fC 1.20/fC 0.80/fC 0.85/fC 0.90/fC 0.85/fC RISE TIME** (SEC) 0.34/fC 0.34/fC 0.34/fC 0.36/fC 0.39/fC 0.39/fC 0.48/fC 0.54/fC 0.54/fC 0.54/fC SETTLING OVERTIME*** SHOOT (SEC) (%) 0.80/fC 0.85/fC 1.15/fC 2.05/fC 2.20/fC 2.20/fC 2.40/fC 4.30/fC 4.50/fC 6.50/fC 0.5 0 1 5 5 5 11 18 20 20
LOWPASS FILTER LTC1064-3 Bessel LTC1164-5 Linear Phase LTC1164-6 Linear Phase LTC1264-7 Linear Phase LTC1164-7 Linear Phase LTC1064-7 Linear Phase LTC1164-5 Butterworth LTC1164-6 Elliptic LTC1064-4 Elliptic LTC1064-1 Elliptic
* To 50% 5%, ** 10% to 90% 5%, *** To 1% 0.5%
9
LTC1164-6
TYPICAL APPLICATI UO
1 VIN V+ 0.1F 2 3 4 5 6 7 LTC1164-6
S
8th Order Elliptic Lowpass Filter (fCLK / fC) = 50:1
14 13 12 11 10 9 8 VOUT fCLK V+ V- 0.1F R C V- V+ NOTES: 1. OPTIONAL OUTPUT BUFFER 1/2RC = 2 x fCUTOFF. 2. PINS 1, 8, 13 CAN BE GROUNDED OR LEFT FLOATING.
1164-6 TA06
-
LT1006
+
8th Order Elliptic Lowpass Filter (fCLK / fC) = 100:1
1 VIN
+
8th Order Linear Phase Lowpass Filter (fCLK / fC) = 160:1
1 VIN
V- 0.1F
14 13 12 LTC1164-6 11 10 9 8
1164-6 TA07
14 13 12 LTC1164-6 11 10 9 8 VOUT fCLK V- 0.1F
2 3
2 3
V
4 5 6 7
fCLK
V+ 0.1F
4 5 6 7
0.1F
VOUT
1164-6 TA08
8th Order 20kHz Cutoff, Elliptic Filter Operating with a Single 5V Supply and Driving 1k, 1000pF Load
1 VIN 2 3 5V 0.1F 10k 4 5 6 7 0.1F 6.65k LTC1164-6 14 13 12 11 10 9 8 510pF
1164-6 TA09
5V
5V NOTES: 1. TOTAL SUPPLY CURRENT IS = 4mA (EXCLUDING OUTPUT LOAD CURRENT). 2. FLAT PASSBAND UP TO 18kHz, f -3dB = 20kHz. 3. THD + NOISE -70dB, 1VP-P VIN 3VP-P, fIN = 1kHz.
1k 5V
fCLK = 1MHz 10k
51.1k
2
- +
7 LT1200 VOUT 1k 1000pF
3
4
10
LTC1164-6
TYPICAL APPLICATI
C2 0.022F R1 1.15k VIN C1 0.1F C3 0.001F R2 76.8k R3 5.62k
+
1/2 LT1013
-
V
+
fC = 1kHz ATTENUATION AT 10kHz = -48dB NOTES: 1. CLOCK-TUNABLE OVER ONE DECADE OF CUTOFF FREQUENCY. 2. BOTH INPUT AND OUTPUT RC ACTIVE FILTERS ARE 0.1dB CHEBYSHEV FILTERS WITH 1kHz RIPPLE BANDWIDTH.
R1 789 VIN C1 0.01F 1 2 3 5V 0.1F 15k 4 5 6 LTC1164-6 IC1
+
1F 10k
7
VS = SINGLE 5V, IS = 5mA TYP 16TH ORDER LOWPASS FILTER FIXED fCUTOFF, fCLK = 540kHz fCUTOFF = 10kHz (fCLK/fC) = 54:1 1/2R1C1 = 1/2R2C2 = 2fCUTOFF
Gain vs Frequency
10 0 -10
THD + NOISE (dB)
-20
GAIN (dB)
-30 -40 -50 -60 -70 -80 -90 1 10 FREQUENCY (kHz) 30
1164-6 TA04
VS = SINGLE 5V IS = 5mA, 16TH ORDER ELLIPTIC LOWPASS fCLK = 540kHz fCUTOFF = 10kHz
Information furnished by Linear Technology Corporation is believed to be accurate and reliable. However, no responsibility is assumed for its use. Linear Technology Corporation makes no representation that the interconnection of its circuits as described herein will not infringe on existing patent rights.
UO
S
8th Order Low Power, Clock-Tunable Elliptic Filter with Active RC Input Anti-Aliasing Filter and Output Smoothing Filter
1 2 3 4 0.1F 5 6 7 LTC1164-6
14 13 12 11 10 9 8 R1 16.9k R2 97.6k C2 0.001F fCLK V- V- 0.1F
-
1/2 LT1013
VOUT
+
C1 0.0047F
100Hz fC 1kHz 10kHz fCLK 100kHz
fC = 1kHz ATTENUATION AT 10kHz = -30dB
1164-6 TA10
Single 5V, 16th Order Lowpass Filter fCUTOFF = 10kHz
14 13 12 11 10 9 8 5V 5V 0.1F 1 2 3 4 5 6 7 LTC1164-6 IC2 14 13 12 11 10 9 8 R2 7.89k 5V VOUT C2 0.001F
fCLK
1k
1164-6 TA03
THD + Noise vs Frequency
-40 -45 -50 -55 -60 -65 -70 -75 -80 -85 -90 1 5 FREQUENCY (kHz) 10
1164-6 TA05
VS = SINGLE 5V IS = 5mA, 16TH ORDER ELLIPTIC LOWPASS VIN = 0.5VRMS fCLK = 540kHz fC = 10kHz
11
LTC1164-6
PACKAGE DESCRIPTIO
0.290 - 0.320 (7.366 - 8.128)
0.008 - 0.018 (0.203 - 0.460) 0.385 0.025 (9.779 0.635)
0 - 15
0.038 - 0.068 (0.965 - 1.727) 0.014 - 0.026 (0.360 - 0.660)
0.300 - 0.325 (7.620 - 8.255)
0.015 (0.380) MIN 0.130 0.005 (3.302 0.127)
0.009 - 0.015 (0.229 - 0.381) +0.025 0.325 -0.015 +0.635 8.255 -0.381
(
)
0.075 0.015 (1.905 0.381)
0.291 - 0.299 (7.391 - 7.595) 0.005 (0.127) RAD MIN
0.010 - 0.029 x 45 (0.254 - 0.737)
0 - 8 TYP SEE NOTE 0.009 - 0.013 (0.229 - 0.330) 0.050 (1.270) TYP 0.004 - 0.012 (0.102 - 0.305) 0.394 - 0.419 (10.007 - 10.643)
SEE NOTE 0.016 - 0.050 (0.406 - 1.270)
NOTE: PIN 1 IDENT, NOTCH ON TOP AND CAVITIES ON THE BOTTOM OF PACKAGES ARE THE MANUFACTURING OPTIONS. THE PART MAY BE SUPPLIED WITH OR WITHOUT ANY OF THE OPTIONS.
12
Linear Technology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7487
(408) 432-1900 q FAX: (408) 434-0507 q TELEX: 499-3977
U
Dimensions in inches (millimeters) unless otherwise noted. J Package 14-Lead Ceramic DIP
0.200 (5.080) MAX 0.015 - 0.060 (0.381 - 1.524) 0.025 (0.635) RAD TYP 0.005 (0.127) MIN 0.785 (19.939) MAX 14 13 12 11 10 9 8
0.220 - 0.310 (5.588 - 7.874)
1 0.100 0.010 (2.540 0.254) 0.125 (3.175) MIN 0.098 (2.489) MAX
2
3
4
5
6
7
J14 0392
N Package 14-Lead Plastic DIP
0.065 (1.651) TYP 14 13 12 0.770 (19.558) MAX 11 10 9 8
0.045 - 0.065 (1.143 - 1.651)
0.260 0.010 (6.604 0.254)
0.018 0.003 (0.457 0.076) 0.100 0.010 (2.540 0.254)
1 0.125 (3.175) MIN
2
3
4
5
6
7
S Package 16-Lead Plastic SOL
16 0.093 - 0.104 (2.362 - 2.642) 0.037 - 0.045 (0.940 - 1.143) 15
0.398 - 0.413 (10.109 - 10.490) 14 13 12 11 10 9
0.014 - 0.019 (0.356 - 0.482) TYP 1 2 3 4 5 6 7 8
SOL16 0392
LT/GP 0293 10K REV 0
(c) LINEAR TECHNOLOGY CORPORATION 1993

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