Datasheet

ManualsBrandsLINEAR TECHNOLOGY ManualsLinear ICsLTC1066-1CSW#PBF

LTC1066-1

10661fa

■

DC Gain Linearity: 14 Bits

■

Maximum DC Offset: ±1.5mV

■

DC Offset TempCo: 7µV/°C

■

Device Fully Tested at f

CUTOFF

= 80kHz

■

Maximum Cutoff Frequency: 120kHz (V

= ±8V)

■

Drives 1kΩ Load with 0.02% THD or Better

■

Signal-to-Noise Ratio: 90dB

■

Input Impedance: 500MΩ

■

Selectable Elliptic or Linear Phase Response

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Operates from Single 5V up to ±8V Power Supplies

■

Available in an 18-Pin SO Wide Package

FREQUENCY (Hz)

100 10k 100k 1M

1066-1 TA02

GAIN (dB)

–10

–20

–30

–40

–50

–60

–70

–80

–90

= 800Hz

= 80kHz

7.5V

1066-1 TA01

–7.5V

7.5V

OUT

;

OS(OUT)

2.5mV

MAX

40kHz ≤ f

CLK

≤ 4MHz

1µF

15pF

OUT A

–IN A

+IN A

–

CONNECT 1

FILTER

OUT

50/100

CLK

OUT B

+IN B

GND

FILTER

COMP 2

CONNECT 2

COMP 1

–

LTC1066-1

20k

30k

SHORT CONNECTION UNDER

IC AND SHIELDED BY A

GROUND PLANE

BYPASS THE POWER SUPPLIES

WITH 0.1µF DISC CERAMIC

■

Instrumentation

■

Data Acquisition Systems

■

Anti-Aliasing Filters

■

Smoothing Filters

■

Audio Signal Processing

APPLICATIO S

FEATURES

DESCRIPTIO

14-Bit DC Accurate

Clock-Tunable, 8th Order Elliptic

or Linear Phase Lowpass Filter

Amplitude Response

Clock-Tunable, DC Accurate, 800Hz to 80kHz Elliptic Lowpass Filter

The LTC

1066-1 is an 8th order elliptic lowpass filter

which simultaneously provides clock-tunability and DC

accuracy. The unique and proprietary architecture of the

filter allows 14 bits of DC gain linearity and a maximum of

1.5mV DC offset. An external RC is required for DC

accurate operation. With ±7.5V supplies, a 20k resistor

and a 1µF capacitor, the cutoff frequency can be tuned

from 800Hz to 100kHz. A clock-tunable 10Hz to 100kHz

operation can also be achieved (see Typical Application

section).

The filter does not require any external active components

such as input/output buffers. The input/output impedance

is 500MΩ/0.1Ω and the output of the filter can source or

sink 40mA. When pin 8 is connected to V

, the clock-to-

cutoff frequency ratio is 50:1 and the input signal is

sampled twice per clock cycle to lower the risk of aliasing.

For frequencies up to 0.75f

CUTOFF

, the passband ripple is

±0.15dB. The gain at f

CUTOFF

is –1dB and the filter’s

stopband attenuation is 80dB at 2.3f

CUTOFF

. Linear phase

operation is also available with a clock-to-cutoff frequency

ratio of 100:1 when pin 8 is connected to ground.

The LTC1066-1 is available in an 18-pin SO Wide package.

TYPICAL APPLICATIO

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

All other trademarks are the property of their respective owners.

Summary of content (20 pages)

PAGE 1
LTC1066-1 14-Bit DC Accurate Clock-Tunable, 8th Order Elliptic or Linear Phase Lowpass Filter U FEATURES DESCRIPTIO ■ The LTC®1066-1 is an 8th order elliptic lowpass filter which simultaneously provides clock-tunability and DC accuracy. The unique and proprietary architecture of the filter allows 14 bits of DC gain linearity and a maximum of 1.5mV DC offset. An external RC is required for DC accurate operation. With ±7.
PAGE 2
LTC1066-1 W U U W W W AXI U RATI GS U ABSOLUTE PACKAGE/ORDER I FOR ATIO (Note 1) TOP VIEW Total Supply Voltage (V + to V –) .......................... 16.5V Power Dissipation ............................................. 700mW Burn-In Voltage ................................................... 16.5V Voltage at Any Input ..... (V – – 0.3V) ≤ VIN ≤ (V + + 0.3V) Maximum Clock Frequency VS = ±8V ....................................................... 6.1MHz VS = ±7.5V ................................
PAGE 3
LTC1066-1 ELECTRICAL CHARACTERISTICS (See Test Circuit) The ● denotes the specifications which apply over the full operating temperature range, otherwise specifications are at VS = ±7.5V, RL = 1k, TA = 25°C, fCLK signal level is TTL or CMOS (maximum clock rise or fall time ≤ 1µs) unless otherwise specified. All AC gain measurements are referenced to passband gain. PARAMETER CONDITIONS MIN TYP MAX UNITS Gain at fCUTOFF for fCLK = 20kHz, VS = ±7.5V fCLK/fCUTOFF = 50:1, f TEST = 400Hz ● – 1.75 – 1.
PAGE 4
LTC1066-1 U W TYPICAL PERFOR A CE CHARACTERISTICS 10 0 –10 fCLK= 500kHz GAIN (dB) –50 –60 VS = ±7.5V TA = 25°C fCLK/fC = 50:1 COMPENSATION = 30k, 15pF –80 –90 –100 –10 –20 –50 –60 VS = ±7.
PAGE 5
LTC1066-1 U W TYPICAL PERFOR A CE CHARACTERISTICS Passband Gain vs Frequency GAIN (dB) 2 1 70 GROUP DELAY (µs) 3 0 –1 B A –2 C D 60 –4 C 40 30 1 10 FREQUENCY (kHz) 2 100 4 6 THD + Noise vs Frequency fIN = 1kHz VS = SINGLE 5V fCLK = 1MHz fCLK /fC = 50:1 TA = 25°C –55 GND PIN 15 AT 2V –65 –70 VS = ±7.5V –80 –50 –75 –80 GND PIN 15 AT 2.5V –55 –60 –65 ( ( –70 –60 –70 –75 –80 –85 –85 –85 –90 0.1 –90 0.
PAGE 6
LTC1066-1 U W TYPICAL PERFOR A CE CHARACTERISTICS Power Supply Current vs Power Supply Voltage Transient Response Transient Response 30 21 1V/DIV 0°C 25°C 70°C 24 1V/DIV POWER SUPPLY CURRENT (mA) 27 18 15 12 9 6 100µs/DIV LINEAR PHASE (PIN 8 TO GND) fIN = 1kHz, fCUTOFF = 10kHz 100µs/DIV ELLIPTIC RESPONSE (PIN 8 TO V +) fIN = 1kHz, fCUTOFF = 10kHz 3 0 0 2 4 6 8 10 12 14 16 18 20 TOTAL POWER SUPPLY VOLTAGE (V) 1066-1 G20 1066-1 G19 1066-1 G18 Table 1.
PAGE 7
LTC1066-1 U U U PIN FUNCTIONS Power Supply Pins (5, 18, 4, 10) The power supply pins should be bypassed with a 0.1µF capacitor to an adequate analog ground. The bypass capacitors should be connected as close as possible to the power supply pins. The V + pins (5, 18) and the V – pins (4, 10) should always be tied to the same positive supply and negative supply value respectively. Low noise linear supplies are recommended.
PAGE 8
LTC1066-1 U U U PIN FUNCTIONS (see Block Diagram). Input bias current flows out of pins 2 and 3. Pin 16 (+IN B) is the positive input of a high performance op amp B which is internally connected as a unity-gain follower. Op amp B buffers the switchedcapacitor network output. The input capacitance of both op amps is 10pF. 15pF capacitor should be connected between pins 11 and 13. Compensation is recommended for the following cases shown in Table 6.
PAGE 9
LTC1066-1 W BLOCK DIAGRA RF CF LTC1066-1 – 2 –IN A HIGH SPEED OP AMP + 3 1 14 OUT A FILTERIN +IN A + V– V 5,18 4,10 CONNECT 1 GND 50/100 CLK 15 8 9 8TH ORDER SWITCHEDCAPACITOR NETWORK 6 11 COMP1 13 COMP2 – 12 CONNECT 2 HIGH SPEED OP AMP 7 + 16 17 OUT B +IN B FILTEROUT PATENT PENDING 11066-1 BD TEST CIRCUIT 20k 1 2 1µF V– VIN 20Ω 0.1µF ELLIPTIC + RESPONSE V 50:1 LINEAR PHASE RESPONSE 100:1 V+ 0.
PAGE 10
LTC1066-1 U W U U APPLICATIONS INFORMATION The DC performance of the LTC1066-1 is dictated by the DC characteristics of the input precision op amp. 1. DC input voltages in the vicinity of the filter’s half of the total power supply are processed with exactly 0dB (or 1V/ V) of gain. 2. The typical DC input voltage ranges are equal to: VIN = ±5.8V, VS = ±7.5V VIN = ±3.6V, VS = ±5V VIN = ±1.4V, VS = ±2.5V With an input DC voltage range of VIN = ±5V, (VS = ±7.5V), the measured CMRR was 100dB.
PAGE 11
LTC1066-1 U W U U APPLICATIONS INFORMATION AC PERFORMANCE AC (Passband) Gain The passband gain of the LTC1066-1 is equal to the passband gain of the internal switched-capacitor lowpass filter, and it is measured at f = 0.25fCUTOFF. Unlike conventional monolithic filters, the LTC1066-1 starts with an absolutely perfect 0dB DC gain and phases into an “imperfect” AC passband gain, typically ±0.1dB. The filter’s low passband ripple, typically 0.05dB, is measured with respect to the AC passband gain.
PAGE 12
LTC1066-1 U W U U APPLICATIONS INFORMATION Transient Response and Settling Time The LTC1066-1 exhibits two different transient behaviors. First, during power-up the DC correcting loop will settle after the voltage offset of the internal switched-capacitor network is stored across the feedback capacitor CF (see Block Diagram). It takes approximately five time constants (5RFCF) for settling to 1%. Second, following DC loop settling, the filter reaches steady state.
PAGE 13
LTC1066-1 U W U U APPLICATIONS INFORMATION Aliasing 0 ALIASED OUTPUT (dB) In a sampled-data system the sampling theorem says that if an input signal has any frequency components greater than one half the sampling frequency, aliasing errors will appear at the output. In practice, aliasing is not always a serious problem. High order switched-capacitor lowpass filters are inherently band limited and significant aliasing occurs only for input signals centered around the clock frequency and its multiples.
PAGE 14
LTC1066-1 U TYPICAL APPLICATIO Dual Supply Operation DC Accurate, 10Hz to 100kHz, Clock-Tunable, 8th Order Elliptic Lowpass Filter fCLK / fC = 50:1 100k 33µF 0.1µF 1 2 100k VIN 3 20Ω –7.5V 7.5V 0.1µF fCLK OUT B +IN A +IN B 5 V+ 8 200Ω –IN A V– 7 7.5V V+ 4 1N4148* 6 0.1µF OUT A 9 LTC1066-1 CONNECT 1 FILTEROUT 50/100 CLK GND FILTERIN COMP 2 CONNECT 2 COMP 1 V– 20Ω 18 7.5V 17 VOUT 0.1µF 16 15 14 13 12 30k 15pF 11 10 0.1µF 1N4148* –7.5V MAXIMUM OUTPUT VOLTAGE OFFSET = ±5.
PAGE 15
LTC1066-1 U TYPICAL APPLICATIO Single 5V Supply Operation DC Accurate, 10Hz to 36kHz, Clock-Tunable, 8th Order Elliptic Lowpass Filter fCLK / fC = 50:1 100k 33µF 0.1µF 1 2 100k 3 VIN 5V fCLK OUT B +IN A +IN B V– V+ 8 200Ω –IN A 5 7 5V V+ 4 6 0.1µF OUT A 9 LTC1066-1 CONNECT 1 FILTEROUT 50/100 CLK GND FILTERIN COMP 2 CONNECT 2 COMP 1 V– 18 5V 17 0.1µF VOUT 16 10k 15 14 13 12 1µF 30k 10k 15pF 11 10 INPUT LINEAR RANGE = 1.4V to 3.6V. DC LINEARITY = ±0.0063%.
PAGE 16
LTC1066-1 U TYPICAL APPLICATIO DC Accurate Lowpass Filter with Input Anti-Aliasing (fCLK ≤ 250kHz) 2ND ORDER BUTTERWORTH ANTIALIASING FILTER PROVIDES –68dB ATTENUATION TO INPUTS AT 2fCLK RF C2 VIN R1 20Ω CF R2 1 C1 2 3 f f 1 fCUTOFF = CLK , = CUTOFF 50 2πRFCF 250 7.5V 20Ω –7.5V 0.1µF 7.5V f –3dB = 2•fCUTOFF (f –3dB IS THE –3dB FREQUENCY OF THE 0.1µF 2ND ORDER ANTI-ALIASING FILTER) 1 = 0.707•f –3dB, R2 = 17.
PAGE 17
LTC1066-1 U TYPICAL APPLICATIO DC Accurate Lowpass Filter with Input Anti-Aliasing (fCLK > 250kHz) 2ND ORDER RC ANTI-ALIASING FILTER PROVIDES –36dB ATTENUATION TO INPUTS AT 2fCLK 402Ω 1k f –3dB IS THE –3dB FREQUENCY OF THE 2ND ORDER RC FILTER f –3dB = 5•fCUTOFF C= 100 f –3dB µF (f –3dB IN Hz) 20Ω 2 C 3 OUT A OUT B +IN A +IN B 4 V– 0.1µF 5 V+ 7.5V 0.1µF 6 7 f fCUTOFF = CLK 50 8 fCLK 9 V + –IN A 20Ω –7.5V 7.
PAGE 18
LTC1066-1 U TYPICAL APPLICATIO DC Accurate Clock-Tunable Lowpass Filter with Tunable Input Anti-Aliasing Filter (Circuit provides at least – 20dB attenuation to input frequencies at 2fCLK. The clock-tunable range is 5 octaves.) 5V 0.1µF 1µF + 1 12.1k 20 LTC1045 2 + 19 0.1µF – 2k FIRST ORDER RC LOWPASS ANTI-ALIASING FILTER 0.1µF 3 + 18 – –5V 5V CLOCK-TUNABLE, 8TH ORDER LOWPASS FILTER 0.1µF 0.1µF 1k 4 4 + 17 0.
PAGE 19
LTC1066-1 U PACKAGE DESCRIPTIO SW Package 18-Lead Plastic Small Outline (Wide .300 Inch) (Reference LTC DWG # 05-08-1620) .050 BSC .045 ±.005 .030 ±.005 TYP .447 – .463 (11.354 – 11.760) NOTE 4 N 18 17 16 15 14 13 12 11 10 N .325 ±.005 .420 MIN .394 – .419 (10.007 – 10.643) NOTE 3 1 2 3 N/2 N/2 RECOMMENDED SOLDER PAD LAYOUT .005 (0.127) RAD MIN .009 – .013 (0.229 – 0.330) NOTE: 1. DIMENSIONS IN .291 – .299 (7.391 – 7.595) NOTE 4 .010 – .029 × 45° (0.254 – 0.
PAGE 20
LTC1066-1 U TYPICAL APPLICATIONS 100kHz Elliptic Lowpass Filter with Input Anti-Aliasing and Output Clock Feedthrough Filters (Not DC Accurate) 2ND ORDER BUTTERWORTH INPUT ANTI-ALIASING FILTER PROVIDES –68dB ATTENUATION TO INPUTS AT 2fCLK. f –3dB = 200kHz 2.49k C1 51pF VIN 10k 2 C2 510pF 3 –8V 0.1µF 8V 0.