FILTER OUTPUT NOISE (V/Hz) LTC1062 5th Order Lowpass Filter FEATURES DESCRIPTIO Lowpass Filter with No DC Error The LTC 1062 is a 5th order all pole maximally flat Low Passband Noise lowpass filter with no DC error. Its unusual architecture Operates DC to 20kHz puts the filter outside the DC path so DC offset and low Operates On a Single 5V Supply or Up to 8V frequency noise problems are eliminated. This makes the 5th Order Filter LTC1062 very useful for lowpass filters where DC accuracy Maximally Flat Response is important. Internal or External Clock The filter input and output are simultaneously taken across Cascadable for Faster Rolloff an external resistor. The LTC1062 is coupled to the signal Buffer Available through an external capacitor. This RC reacts with the internal switched capacitor network to form a 5th order U rolloff at the output. APPLICATIO S The filter cutoff frequency is set by an internal clock that 60Hz Lowpass Filters can be externally driven. The clock-to-cutoff frequency Antialiasing Filter ratio is typically 100:1, allowing the clock ripple to be Low Level Filtering easily removed. Rolling Off AC Signals from High DC Voltages Digital Voltmeters Two LTC1062s can be cascaded to form a 10th order quasi Scales max flat lowpass filter. The device can be operated with Strain Gauges single or dual supplies ranging from 2.5V to 9V. The LTC1062 is manufactured using Linear Technologys TM enhanced LTCMOS silicon gate process. , LTC and LT are registered trademarks of Linear Technology Corporation. LTCMOS is a trademark of Linear Technology Corporation. TYPICAL APPLICATIO 10Hz 5th Order Butterworth Lowpass Filter Filter Amplitude Response and Noise 25.8k 0 DC ACCURATE C = 3900pF OSC V IN OUTPUT 10 1F 20 1 8 BUFFERED FB B OUT OUTPUT 30 2 7 AGND OUT 40 LTC1062 50 50 3 6 + V = 5V V V 60 40 4 5 DIVIDER C OSC RATIO 70 30 80 20 C OSC= 3900pF 90 10 + V = 5V 1062 TA01 100 0 1 10 100 NOTE: TO ADJUST OSCILLATOR FREQUENCY, INPUT FREQUENCY (Hz) USE A 6800pF CAPACITOR IN SERIES 1062 TA02 WITH A 50k POT FROM PIN 5 TO GROUND 1062fd 1 AMPLITUDE RESPONSE (dB) U ULTC1062 ABSOLUTE AXI U RATI GS (Note 1) + Total Supply Voltage (V to V ) ............................... 18V Storage Temperature Range ................. 65C to 150C + Input Voltage at Any Pin ..... V 0.3V V V + 0.3V Lead Temperature (Soldering, 10 sec)................. 300C IN Operating Temperature Range LTC1062M (OBSOLETE)............. 55C T 125C A LTC1062C ................................... 40C T 85C A UUW PACKAGE/ORDER I FOR ATIO TOP VIEW ORDER PART ORDER PART TOP VIEW NUMBER NUMBER FB 1 8 B OUT NC 1 16 NC AGND 2 7 OUT NC 2 15 NC LTC1062CN8 LTC1062CSW + V 3 V 6 FB 3 14 B OUT DIVIDER 4 5 C AGND 4 13 OUT OSC RATIO + V 5 12 V N8 PACKAGE DIVIDER 8-LEAD PDIP 6 11 C OSC RATIO T = 100C, = 130C/W NC 7 10 NC J MAX JA NC 8 9 NC J8 PACKAGE 8-LEAD CERDIP LTC1062MJ8 T = 150C, = 100C/W SW PACKAGE J MAX JA LTC1062CJ8 16-LEAD PLASTIC SO T = 150C, = 90C/W J MAX JA OBSOLETE PACKAGE Consider the N8 Package as an Alternate Source Consult LTC Marketing for parts specified with wider operating temperature ranges. ELECTRICAL CHARACTERISTICS The denotes specifications which apply over the full operating tempera- + ture range, otherwise specifications are at T = 25C. V = 5V, V = 5V, unless otherwise specified. AC output measured at Pin 7, A Figure 1. PARAMETER CONDITIONS MIN TYP MAX UNITS Power Supply Current C (Pin 5 to V , Pin 11 in SW16) = 100pF 4.5 7 mA OSC 10 mA Input Frequency Range 0 to 20 kHz + Filter Gain at f = 0 f = 100kHz, Pin 4 (Pin 6 in SW16) at V, 0.00 dB IN CLK = 0.5f (Note 2) C = 0.01F, R = 25.78k 0.02 0.3 dB f IN C f = f 2 3.00 dB IN C f = 2f 2830.00 dB IN C = 4f 5260.00 dB f IN C + Clock-to-Cutoff Frequency Ratio, f /f f = 100kHz, Pin 4 (Pin 6 in SW16) at V,100 1% CLK C CLK C = 0.01F, R = 25.78k + Filter Gain at f = 16kHz f = 400kHz, Pin 4 at V , C = 0.01F, R = 6.5k 43 52 dB IN CLK + f /f Tempco f = 400kHz, Pin 4 at V , C = 0.01F, R = 6.5k 10 ppm/C CLK C CLK Filter Output (Pin 7, Pin 13 in SW16) DC Swing Pin 7/Pin13 (SW16) Buffered with an External Op Amp 3.5 3.8 V Clock Feedthrough 1mV P-P 1062fd 2 U WWW