LTC1569CS8-7#PBF

LTC1569-7 Linear Phase, DC Accurate, Tunable, 10th Order Lowpass Filter Furthermore, its root raised cosine response offers the optimum pulse shaping for PAM data communications. The filter attenuation is 57dB at 1.5 • fCUTOFF, 60dB at 2 • fCUTOFF, and in excess of 80dB at 6 • fCUTOFF. DC-accuracysensitive applications benefit from the 5mV maximum DC offset. FEATURES ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ One External R Sets Cutoff Frequency Root Raised Cosine Response Up to 300kHz Cutoff on a Single 5V Supply Up to 150kHz Cutoff on a Single 3V Supply 10th Order, Linear Phase Filter in an SO-8 DC Accurate, VOS(MAX) = 5mV Low Power Modes Differential or Single-Ended Inputs 80dB CMRR (DC) 80dB Signal-to-Noise Ratio, VS = 5V Operates from 3V to ±5V Supplies U APPLICATIO S ■ ■ ■ Data Communication Filters for 3V Operation Linear Phase and Phase Matched Filters for I/Q Signal Processing Pin Programmable Cutoff Frequency Lowpass Filters U DESCRIPTIO The LTC®1569-7 is a 10th order lowpass filter featuring linear phase and a root raised cosine amplitude response. The high selectivity of the LTC1569-7 combined with its linear phase in the passband makes it suitable for filtering both in data communications and data acquisition sytems. The LTC1569-7 is the first sampled data filter which does not require an external clock yet its cutoff frequency can be set with a single external resistor with a typical accuracy of 3.5% or better. The external resistor programs an internal oscillator whose frequency is divided by either 1, 4 or 16 prior to being applied to the filter network. Pin 5 determines the divider setting. Thus, up to three cutoff frequencies can be obtained for each external resistor value. Using various resistor values and divider settings, the cutoff frequency can be programmed over a range of seven octaves. Alternatively, the cutoff frequency can be set with an external clock and the clock-to-cutoff frequency ratio is 32:1. The ratio of the internal sampling rate to the filter cutoff frequency is 64:1. The LTC1569-7 is fully tested for a cutoff frequency of 256kHz/128kHz with single 5V/3V supply although up to 300kHz cutoff frequencies can be obtained. The LTC1569-7 features power savings modes and it is available in an SO-8 surface mount package. , LTC and LT are registered trademarks of Linear Technology Corporation. U TYPICAL APPLICATION Frequency Response, fCUTOFF = 128kHz/32kHz/8kHz Single 3V Supply, 128kHz/32kHz/8kHz Lowpass Filter 3V 1 2 OUT IN – V+ 8 7 VOUT –20 REXT = 10k 3V 1µF LTC1569-7 3.48k 3 2k IN + GND RX 6 1µF V– DIV/CLK fCUTOFF = –80 1/1 100pF –100 128kHz (10k/REXT) 1, 4 OR 16 –60 1/4 5 EASY TO SET fCUTOFF: –40 3V 1/16 4 GAIN (dB) VIN 0 1569-7 TA01 1 10 100 FREQUENCY (kHz) 1000 1569-7 TA01a 1 LTC1569-7 U U RATI GS W W W W AXI U U ABSOLUTE PACKAGE/ORDER I FOR ATIO (Note 1) Total Supply Voltage ................................................ 11V Power Dissipation .............................................. 500mW Operating Temperature LTC1569C ............................................... 0°C to 70°C LTC1569I ............................................ – 40°C to 85°C Storage Temperature ............................ – 65°C to 150°C Lead Temperature (Soldering, 10 sec).................. 300°C ORDER PART NUMBER TOP VIEW IN + 1 8 OUT – 2 7 V+ GND 3 6 RX V– 4 5 DIV/CLK IN LTC1569CS8-7 LTC1569IS8-7 S8 PART MARKING S8 PACKAGE 8-LEAD PLASTIC SO TJMAX = 125°C, θJA = 80°C/W (Note 6) 15697 1569I7 Consult factory for Military grade parts. ELECTRICAL CHARACTERISTICS The ● denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. VS = 3V (V + = 3V, V – = 0V), fCUTOFF = 128kHz, RLOAD = 10k unless otherwise specified. PARAMETER CONDITIONS Filter Gain VS = 5V, fCLK = 8.192MHz, fCUTOFF = 256kHz, VIN = 2.5VP-P, REXT = 5k, Pin 5 Shorted to Pin 4 fIN = 5120Hz = 0.02 • fCUTOFF fIN = 51.2kHz = 0.2 • fCUTOFF fIN = 128kHz = 0.5 • fCUTOFF fIN = 204.8kHz = 0.8 • fCUTOFF fIN = 256kHz = fCUTOFF, LTC1569C fIN = 256kHz = fCUTOFF, LTC1569I fIN = 384kHz = 1.5 • fCUTOFF fIN = 512kHz = 2 • fCUTOFF fIN = 768kHz = 3 • fCUTOFF VS = 2.7V, fCLK = 1MHz, fIN = 625Hz = 0.02 • fCUTOFF fIN = 6.25kHz = 0.2 • fCUTOFF fCUTOFF = 31.25kHz, VIN = 1VP-P, Pin 6 Shorted to Pin 4, External Clock fIN = 15.625kHz = 0.5 • fCUTOFF fIN = 25kHz = 0.8 • fCUTOFF fIN = 31.25kHz = fCUTOFF fIN = 46.875kHz = 1.5 • fCUTOFF fIN = 62.5kHz = 2 • fCUTOFF fIN = 93.75kHz = 3 • fCUTOFF Filter Phase VS = 2.7V, fCLK = 4MHz, fCUTOFF = 125kHz, Pin 6 Shorted to Pin 4, External Clock Filter Cutoff Accuracy when Self-Clocked REXT = 10.24k from Pin 6 to Pin 7, VS = 3V, Pin 5 Shorted to Pin 4 Filter Output DC Swing VS = 3V, Pin 3 = 1.11V fIN = 2500Hz = 0.02 • fCUTOFF fIN = 25kHz = 0.2 • fCUTOFF fIN = 62.5kHz = 0.5 • fCUTOFF fIN = 100kHz = 0.8 • fCUTOFF fIN = 125kHz = fCUTOFF fIN = 187.5kHz = 1.5 • fCUTOFF MIN TYP MAX UNITS ● ● ● ● ● ● ● ● ● – 0.10 – 0.25 – 0.50 – 1.1 – 5.7 – 6.2 0.00 – 0.15 – 0.41 – 0.65 – 3.8 – 3.8 – 58 – 62 – 67 0.10 – 0.05 – 0.25 – 0.40 – 2.3 – 2.0 – 48 – 54 – 64 dB dB dB dB dB dB dB dB dB ● ● ● ● ● ● ● ● – 0.08 – 0.25 – 0.50 – 0.75 – 3.3 0.00 – 0.15 – 0.40 – 0.65 – 3.15 – 57 – 60 – 66 0.12 – 0.05 – 0.30 – 0.50 – 3.0 – 52 – 54 – 58 dB dB dB dB dB dB dB dB ● ● ● ● – 114 78 – 85 155 –11 –112 80 – 83 158 – 95 –110 82 – 81 161 Deg Deg Deg Deg Deg Deg 125kHz ±1% 2.1 VP-P VP-P 3.9 VP-P VP-P 8.6 8.4 VP-P VP-P 8.0 VP-P ● 1.9 ● 3.7 LTC1569C ● LTC1569I ● VS = 5V, Pin 3 = 2V VS = ±5V 2 LTC1569-7 ELECTRICAL CHARACTERISTICS The ● denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. VS = 3V (V + = 3V, V – = 0V), fCLK = 4.096MHz, fCUTOFF = 128kHz, RLOAD = 10k unless otherwise specified. PARAMETER Output DC Offset (Note 2) CONDITIONS REXT = 10k, Pin 5 Shorted to Pin 4 Output DC Offset Drift Clock Pin Logic Thresholds when Clocked Externally Power Supply Current (Note 3) VS = 3V VS = 5V VS = ±5V MIN TYP ±2 ±6 ±15 REXT = 10k, Pin 5 Shorted to Pin 4 VS = 3V VS = 5V VS = ±5V – 25 – 25 ±25 µV/°C µV/°C µV/°C VS = 3V Min Logical “1” Max Logical “0” 2.6 0.5 V V VS = 5V Min Logical “1” Max Logical “0” 4.0 0.5 V V VS = ±5V Min Logical “1” Max Logical “0” 4.0 0.5 V V fCLK = 1.028MHz (10k from Pin 6 to Pin 7, Pin 5 Open, ÷ 4), fCUTOFF = 32kHz VS = 3V 8 9 mA mA 7 9 10 mA mA 9 13 14 mA mA 14 mA mA 30 mA mA 37 mA mA 4.6 V ● VS = 10V ● fCLK = 4.096MHz (10k from Pin 6 to Pin 7, Pin 5 Shorted to Pin 4, ÷ 1), fCUTOFF = 128kHz VS = 3V fCLK = 8.192MHz (5k from Pin 6 to Pin 7, Pin 5 Shorted to Pin 4, ÷ 1), fCUTOFF = 256kHz VS = 5V 9.5 ● 20 ● VS = 10V 27 ● Power Supply Voltage where Low Power Mode is Enabled Pin 5 Shorted to Pin 4, Note 3 ● 3.7 UNITS mV mV mV 6 ● VS = 5V MAX ±5 ±12 4.2 Clock Feedthrough REXT = 10k, Pin 5 Open 0.4 mVRMS Wideband Noise Noise BW = DC to 2 • fCUTOFF 125 µVRMS THD fIN = 10kHz, 1.5VP-P 74 dB Clock-to-Cutoff Frequency Ratio 32 Max Clock Frequency (Note 4) VS = 3V VS = 5V VS = ±5V Min Clock Frequency (Note 5) 3V to ±5V, TA < 85°C Input Frequency Range Aliased Components 1dB of gain peaking. Note 5: The minimum clock frequency is arbitrarily defined as the frequecy at which the filter DC offset changes by more than 5mV. Note 6: Thermal resistance varies depending upon the amount of PC board metal attached to the device. θJA is specified for a 2500mm2 test board covered with 2oz copper on both sides. 3 LTC1569-7 U W TYPICAL PERFOR A CE CHARACTERISTICS Passband Gain and Group Delay vs Frequency Gain vs Frequency 10 20 VS = 3V fC = 128kHz 19 REXT = 10k PIN 5 AT V – 18 17 1 0 16 GAIN (dB) –1 15 14 –2 DELAY (µs) LOG MAG (10dB/DIV) VS = 3V fC = 128kHz REXT = 10k PIN 5 AT V – 13 12 –3 11 –90 5 10 100 FREQUENCY (kHz) –4 1000 10 FREQUENCY (kHz) 1 1569-7 G03 1569-7 G04 THD vs Input Voltage THD vs Input Frequency 12 VS = 3V PIN 3 = 1.11V –60 VS = 5V PIN 3 = 2V THD (dB) –72 –74 VIN = 1.5VP-P fCUTOFF = 128kHz IN + TO OUT REXT = 10k PIN 5 AT V – –76 10 –70 1 2 3 4 INPUT VOLTAGE (VP-P) DIV-BY-16 6 DIV-BY-4 5 5 1 10 100 fCUTOFF (kHz) ± 5V Supply Current 35 23 32 21 DIV-BY-1 19 17 DIV-BY-1 29 26 ISUPPLY (mA) EXT CLK 15 13 11 23 EXT CLK 20 17 14 9 11 DIV-BY-16 7 DIV-BY-16 DIV-BY-4 8 DIV-BY-4 5 5 1 10 100 fCUTOFF (kHz) 1000 1569-7 G06 1 1000 1569-7 G05 1569-7 G02 5V Supply Current ISUPPLY (mA) EXT CLK 7 4 0 10 20 30 40 50 60 70 80 90 100 INPUT FREQUENCY (kHz) 1569-7 G01 4 8 –90 0 DIV-BY-1 9 fIN = 10kHz fCUTOFF = 128kHz IN + TO OUT REXT = 10k PIN 5 AT V – –80 –78 11 VS = 5V PIN 3 = 2V ISUPPLY (mA) –70 THD (dB) 3V Supply Current –50 –68 10 100 10 100 fCUTOFF (kHz) 1000 1569-7 G07 LTC1569-7 U U U PIN FUNCTIONS IN +/IN – (Pins 1, 2): Signals can be applied to either or both input pins. The DC gain from IN + (Pin 1) to OUT (Pin␣ 8) is 1.0, and the DC gain from Pin 2 to Pin 8 is –1. The input range, input resistance and output range are described in the Applications Information section. Input voltages which exceed the power supply voltages should be avoided. Transients will not cause latchup if the current into/out of the input pins is limited to 20mA. DIV/CLK (Pin 5): DIV/CLK serves two functions. When the internal oscillator is enabled, DIV/CLK can be used to engage an internal divider. The internal divider is set to 1:1 when DIV/CLK is shorted to V – (Pin 4). The internal divider is set to 4:1 when DIV/CLK is allowed to float (a 100pF bypass to V – is recommended). The internal divider is set to 16:1 when DIV/CLK is shorted to V + (Pin 7). In the divide-by-4 and divide-by-16 modes the power supply current is reduced by typically 60%. GND (Pin 3): The GND pin is the reference voltage for the filter and should be externally biased to 2V (1.11V) to maximize the dynamic range of the filter in applications using a single 5V (3V) supply. For single supply operation, the GND pin should be bypassed with a quality 1µF ceramic capacitor to V – (Pin 4). The impedance of the circuit biasing the GND pin should be less than 2kΩ as the GND pin generates a small amount of AC and DC current. For dual supply operation, connect Pin␣ 3 to a high quality DC ground. A ground plane should be used. A poor ground will increase DC offset, clock feedthrough, noise and distortion. When the internal oscillator is disabled (RX shorted to V –) DIV/CLK becomes an input pin for applying an external clock signal. For proper filter operation, the clock waveform should be a squarewave with a duty cycle as close as possible to 50% and CMOS voltages levels (see Electrical Characteristics section for voltage levels). DIV/ CLK pin voltages which exceed the power supply voltages should be avoided. Transients will not cause latchup if the fault current into/out of the DIV/CLK pin is limited to 40mA. RX (Pin 6): Connecting an external resistor between the RX pin and V + (Pin 7) enables the internal oscillator. The value of the resistor determines the frequency of oscillation. The maximum recommended resistor value is 40k and the minimum is 3.8k/8k (single 5V/3V supply). The internal oscillator is disabled by shorting the RX pin to V – (Pin 4). (Please refer to the Applications Information section.) V –/V + (Pins 4, 7): For 3V, 5V and ±5V applications a quality 1µF ceramic bypass capacitor is required from V + (Pin 7) to V – (Pin 4) to provide the transient energy for the internal clock drivers. The bypass should be as close as possible to the IC. In dual supply applications (Pin 3 is grounded), an additional 0.1µF bypass from V + (Pin 7) to GND (Pin 3) and V – (Pin 4) to GND (Pin 3) is recommended. OUT (Pin 8): Filter Output. This pin can drive 10kΩ and/or 40pF loads. For larger capacitive loads, an external 100Ω series resistor is recommended. The output pin can exceed the power supply voltages by up to ±2V without latchup. The maximum voltage difference between GND (Pin 3) and V + (Pin 7) should not exceed 5.5V. W BLOCK DIAGRA IN + 1 8 OUT 10TH ORDER LINEAR PHASE FILTER NETWORK IN – 2 7 V+ REXT GND 3 V– 4 POWER CONTROL 6 RX DIVIDER/ BUFFER 5 DIV/CLK PRECISION OSCILLATOR 1569-7 BD 5 LTC1569-7 U U W U APPLICATIONS INFORMATION Self-Clocking Operation The LTC1569-7 features a unique internal oscillator which sets the filter cutoff frequency using a single external resistor. The design is optimized for VS = 3V, fCUTOFF = 128kHz, where the filter cutoff frequency error is typically