Datasheet

ManualsBrandsLINEAR TECHNOLOGY ManualsLinear ICsLTC1067CGN#PBF

LTC1067/LTC1067-50

Rail-to-Rail, Very Low Noise

Universal Dual Filter Building Block

FEATURES

DESCRIPTION

The LTC

1067/LTC1067-50 consist of two identical rail-

to-rail, high accuracy and very wide dynamic range 2nd

order switched-capacitor building blocks. Each building

block, together with three to five resistors, provides 2nd

order filter functions such as bandpass, highpass, lowpass,

notch and allpass. High precision 4th order filters are

easily designed.

The center frequency of each 2nd order section is tuned by

the external clock frequency. The internal clock-to-center

frequency ratio (100:1 for the LTC1067 and 50:1 for the

LTC1067-50) can be modified by the external resistors.

These devices have a double sampled architecture which

places aliasing and imaging components at twice the clock

frequency. The LTC1067-50 is a low power device con-

suming about one half the current of the LTC1067. The

LTC1067-50’s typical supply current is about 1mA from a

3.3V supply.

The LTC1067 and LTC1067-50 are available in 16-pin

narrow SSOP and SO packages.

Mask programmable versions of the LTC1067 and

LTC1067-50, with thin film resistors on-chip and custom

clock-to-cutoff frequency ratios, can be designed in an

SO-8 package to realize application specific monolithic

filters. Please contact LTC Marketing for more details.

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

TYPICAL APPLICATION

Frequency Response

FREQUENCY (kHz)

GAIN (dB)

1067 • TA02

–10

–20

–30

–40

0.1µF

1067 TA01

LTC1067-50

LPA

BPA

HPA/NA

INV A

CLK

AGND

–

LPB

BPB

HPB/NB

INV B

3.3V

R32, 200k

R22, 10k

R31, 200k

R21, 10k

R11

200k

RB1, 200k

OUT

1µF

CLK

= 500kHz

TOTAL OUTPUT NOISE: 90µV

RMS

S/N RATIO: 80dB

■

Rail-to-Rail Input and Output Operation

■

Operates from a Single 3V to

5V Supply

■

Dual 2nd Order Filter in a 16-Lead SSOP Package

■

> 80dB Dynamic Range on Single 3.3V Supply

■

Clock-to-Center Frequency Ratio of 100:1 for the

LTC1067 and 50:1 for the LTC1067-50

■

Internal Sampling-to-Center Frequency Ratio of

200:1 for the LTC1067 and 100:1 for the LTC1067-50

■

Center Frequency Error < ±0.2% Typ

■

Low Noise: < 40µV

RMS

, Q ≤ 5

■

Customizable with Internal Resistors

APPLICATIONS

■

Notch Filters

■

Narrowband Bandpass Filters

■

Tone Detection

■

Noise Reduction Systems

Single 3.3V Supply Rail-to-Rail,

4th Order, 10kHz Bandpass Filter

Summary of content (20 pages)

PAGE 1
LTC1067/LTC1067-50 Rail-to-Rail, Very Low Noise Universal Dual Filter Building Block U DESCRIPTION FEATURES ■ ■ ■ ■ ■ ■ ■ ■ ■ Rail-to-Rail Input and Output Operation Operates from a Single 3V to ±5V Supply Dual 2nd Order Filter in a 16-Lead SSOP Package > 80dB Dynamic Range on Single 3.
PAGE 2
LTC1067/LTC1067-50 U PACKAGE/ORDER INFORMATION U W W V –) W .............................. 12V Input Voltage ........................ (V + + 0.3V) to (V – – 0.3V) Output Short-Circuit Duration .......................... Indefinite Power Dissipation ............................................... 500mV Operating Temperature Range LTC1067C ............................................... 0°C to 70°C LTC1067I ............................................ – 40°C to 85°C Storage Temperature Range ...........
PAGE 3
LTC1067/LTC1067-50 ELECTRICAL CHARACTERISTICS LTC1067 (complete filter) VS = 4.75V, fCLK = 250kHz, TA = 25°C, unless otherwise noted. PARAMETER Q Accuracy fO Temperature Coefficient Q Temperature Coefficient DC Offset Voltage (See Table 2) Clock Feedthrough Maximum Clock Frequency Power Supply Current CONDITIONS VS = 3V, fCLK = 250kHz, Q = 5 VS = 4.
PAGE 4
LTC1067/LTC1067-50 ELECTRICAL CHARACTERISTICS LTC1067-50 (complete filter) VS = 4.75V, fCLK = 125kHz, TA = 25°C, unless otherwise noted. PARAMETER fO Temperature Coefficient Q Temperature Coefficient DC Offset Voltage (See Table 2) CONDITIONS Clock Feedthrough Maximum Clock Frequency Power Supply Current MIN VOS1 (DC Offset of Input Inverter) VOS2 (DC Offset of First Integrator) VOS3 (DC Offset of Second Integrator) ● ● ● Q < 2.5, VS = ±5V VS = 3V, fCLK = 125kHz VS = 4.
PAGE 5
LTC1067/LTC1067-50 U W TYPICAL PERFORMANCE CHARACTERISTICS LTC1067 Noise + THD vs Input Frequency LTC1067 Noise + THD vs Input Frequency –75 MODE 1 –80 MODE 3 –85 4TH ORDER BUTTERWORTH LPF VS = SINGLE 5V, fCLK = 500kHz VIN = 0.5VRMS, f–3dB = 5kHz, RL = 20k 220 4TH ORDER LOWPASS BUTTERWORTH VS = ±5V, VIN = 1VRMS fCLK = 1MHz, f–3dB = 10kHz RL = 20k –80 200 160 MODE 1 –85 3 2 INPUT FREQUENCY (kHz) 4 5 3 2 4 5 6 7 8 9 10 INPUT FREQUENCY (MHz) 9.0 8.8 8.6 8.4 4.5 4.5 VS = 5V 4.0 3.5 VS = 3.
PAGE 6
LTC1067/LTC1067-50 U W TYPICAL PERFORMANCE CHARACTERISTICS LTC1067-50 Noise + THD vs Input Voltage LTC1067-50 Noise + THD vs Input Voltage –20 4TH ORDER BUTTERWORTH LPF VS = SINGLE 5V, fIN = 1kHz fCLK = 250kHz, f–3dB = 5kHz RL = 20k –40 –30 (NOISE + THD)/SIGNAL (dB) –30 –50 –60 –70 MODE 1 –80 –90 –40 1 INPUT VOLTAGE (VRMS) MODE 1 –65 –50 –60 MODE 3 MODE 2 –70 –80 MODE 1 –100 0.
PAGE 7
LTC1067/LTC1067-50 U W TYPICAL PERFORMANCE CHARACTERISTICS LTC1067/LTC1067-50 Mode 3 Noise Increase vs R2/R4 Ratio 2.0 2.0 1.9 1.9 RELATIVE NOISE INCREASE (REFERENCE NOISE WHEN R2/R4 = 1) RELATIVE NOISE INCREASE (REFERENCE NOISE WHEN R5/R6 = 0.02) LTC1067/LTC1067-50 Mode 1B Noise Increase vs R5/R6 Ratio 1.8 1.7 1.6 1.5 1.4 1.3 1.2 1.1 0.5 1.5 2.0 2.5 R5/R6 RATIO 1.0 3.0 1.7 1.6 1.5 1.4 1.3 1.2 1.1 1.0 0.2 1.0 0 1.8 3.5 0.3 0.4 0.5 0.6 0.7 R2/R4 RATIO 0.8 0.9 1.
PAGE 8
LTC1067/LTC1067-50 U U U PIN FUNCTIONS SA, SB (Pins 4, 13): Summing Inputs. The summing pins’ connection, along with the other resistor connections, determine the circuit topology (mode) of each 2nd order section. These pins should never be left floating. LPA, BPA, HPA/NA, HPB/NB, BPB, LPB (Pins 5, 6, 7, 10, 11, 12): Output Pins. Each 2nd order section of the LTC1067 has three outputs which typically source 33mA and sink 2mA.
PAGE 9
LTC1067/LTC1067-50 W U ODES OF OPERATIO Linear Technology’s universal switched-capacitor filters are designed with a fixed internal, nominal fCLK/fO ratio. The LTC1067 has a 100:1 f CLK /f O ratio and the LTC1067-50 has a 50:1 fCLK/fO ratio. Filter designs often require the fCLK /fO ratio of each section to be different from the nominal ratio and in most cases different from each other. Ratios other than the nominal value are possible with external resistors.
PAGE 10
LTC1067/LTC1067-50 W U ODES OF OPERATIO CC R6 Please refer to the Operating Limits paragraph under Applications Information for a guide to the use of capacitor CC. R5 CC R3 R4 R2 S N VIN R1 – + Σ + AGND NOTE: RATIO = 100 FOR LTC1067 = 50 FOR LTC1067-50 LP BP R2 – ∫ HP ∫ 1067 F04 √ fCLK R6 fO = ; f n = fO RATIO (R6 + R5) R3 R6 ; H = – R2 ; H Q = R3 =– R1 R1 OBP R2 (R6 + R5) ON R2 R6 + R5 HOLP = – R6 R1 √ R3 ( VIN R1 – S + Σ – ∫ + ) fCLK RATIO 1 R3 R2 R2 R3 √ R4 ; Q = 1.
PAGE 11
LTC1067/LTC1067-50 W U ODES OF OPERATIO Mode 3a Mode 2n This is an extension of Mode 3 where the highpass and lowpass outputs are summed through two external resistors, RH and RL, to create a notch (see Figure 7). Mode 3a is more versatile than Mode 2 because the notch frequency can be higher or lower than the center frequency of the 2nd order section. The external op amp of Figure 7 is not always required.
PAGE 12
LTC1067/LTC1067-50 U U W U APPLICATIONS INFORMATION A switched-capacitor integrator generally exhibits a higher input offset than a discrete RC integrator. The larger offset is mainly due to the charge injection from the CMOS switches into the integrated capacitor. The integrator’s op amp offset, typically a couple of millivolts, also adds to the overall offset value. Figure 9 shows the input offsets from a single 2nd order section.
PAGE 13
LTC1067/LTC1067-50 U W U U APPLICATIONS INFORMATION Aliasing Aliasing is an inherent phenomenon of switched-capacitor filters and occurs when the frequency of the input signals that produce the strongest aliased components have a frequency, fIN, such as (fSAMPLING – fIN) that falls into the filter’s passband. For both the LTC1067 and the LTC1067-50, the sampling frequency is twice fCLK. If the input signal spectrum is not band limited, aliasing may occur.
PAGE 14
LTC1067/LTC1067-50 U U W U APPLICATIONS INFORMATION POSITIVE OUTPUT VOLTAGE SWING (V) 5.0 4.5 LTC1067 4.0 LTC1067-50 3.5 3.0 2.5 0 2 4 6 8 10 12 14 16 18 20 LOAD RESISTANCE (kΩ TO V –) 1067 F11 Figure 11. LTC1067/LTC1067-50 Positive Output Voltage Swing vs Load Resistance, 5V Supply POSITIVE OUTPUT VOLTAGE SWING (V) 3.3 LTC1067 VS = 3.3V 3.0 2.7 LTC1067-50 VS = 3V 2.4 2.1 1.8 1.5 0 2 4 6 8 10 12 14 16 18 20 LOAD RESISTANCE (kΩ TO V –) 1067 F12 Figure 12.
PAGE 15
LTC1067/LTC1067-50 U U W U APPLICATIONS INFORMATION Figure 14 illustrates how a resistor adjusts the AGND voltage for use with a 3V/3.3V powered ADC with a fullscale input of 2.048V. As in the previous circuit, the resistor value was chosen carefully to assure that a 2.048V input signal to the filter yields a full-scale reading from the ADC and a 0V input signal gives the lowest possible value. For this application, the power supply must be above 2.
PAGE 16
LTC1067/LTC1067-50 U U W U APPLICATIONS INFORMATION This would be used for operating Mode 3. Here, a 0Ω resistor in the R61 position also works. Jumpers JP52 and JP62 perform the same functions on the B side of the part. Several other jumpers should be connected as follows: The buffering amplifier can be configured for inverting or noninverting operation. For inverting applications, connect jumper JP2 positions 1 and 2.
PAGE 17
LTC1067/LTC1067-50 U U W U APPLICATIONS INFORMATION Figure 16. Silkscreen for the LTC1067/LTC1067-50 Demo Board U TYPICAL APPLICATIONS 5th Order Lowpass with Input RC (Fixed Frequency) 1 5V 0.1µF 2 3 4 R41, 20k R31, 47.5k VIN RIN1 16.9k 5 RIN2 22.6k 6 R21, 22.6k 7 8 CIN1 1500pF 5% V+ CLK NC AGND 16 14 V– V+ SA SB LTC1067 LPA LPB BPA BPB HPA/NA HPB/NB INV A INV B fCLK 15 –5V 0.1µF 13 12 R42, 47.5k 11 R32, 29.4k 10 R22, 45.
PAGE 18
LTC1067/LTC1067-50 U TYPICAL APPLICATIONS 1kHz Linear Phase Bandpass Filter 1 5V 0.1µF R61 40.2k 2 3 4 R51 4.99k 5 R31, 56.2k 6 R21, 10k 7 R11 60.4k 8 VIN V+ CLK AGND NC 16 100kHz 15 –5V 0.1µF 14 V– V+ SA SB LTC1067 LPA LPB BPA BPB HPA/NA HPB/NB INV A INV B 13 12 R42, 80.6k 11 R32, 53.6k 10 R22, 10k VS MAXIMUM FREQUENCY CENTER 9 RB1, 36.5k ±5V 5kHz 5V (OR ±2.5V) 3V (OR ±1.5V) 2.5kHz 2.
PAGE 19
LTC1067/LTC1067-50 U TYPICAL APPLICATIONS Single Supply, 4th Order Bandpass Filter VS = 5V, fCLK = 64kHz Gain vs Frequency Gain vs Frequency Sine Burst Response 1 0 0 5 –1 10 –2 15 –3 GAIN (dB) GAIN (dB) –5 20 25 –4 VOUT (50mV/DIV) –5 30 –6 35 –7 40 –8 45 500 VIN (500mV/DIV) –9 700 900 1100 1300 FREQUENCY (kHz) 1500 960 980 1000 1020 FREQUENCY (kHz) 1067 TA07b 1040 5ms/DIV 1067 TA07d 1067 TA07b LTC1067 Dual Bandpass Filters VS = ±5V, fCLK = 150kHz (fCENTER1 =1.
PAGE 20
LTC1067/LTC1067-50 U PACKAGE DESCRIPTION Dimensions in inches (millimeters) unless otherwise noted. S Package 16-Lead Plastic Small Outline (Narrow 0.150) (LTC DWG # 05-08-1610) 0.386 – 0.394* (9.804 – 10.008) 0.010 – 0.020 × 45° (0.254 – 0.508) 0.008 – 0.010 (0.203 – 0.254) 16 0.004 – 0.010 (0.101 – 0.254) 0.053 – 0.069 (1.346 – 1.752) 15 14 13 12 11 10 9 0° – 8° TYP 0.150 – 0.157** (3.810 – 3.988) 0.228 – 0.244 (5.791 – 6.197) 0.050 (1.270) TYP 0.014 – 0.019 (0.355 – 0.483) 0.016 – 0.