19-4766; Rev 1; 9/98 5th-Order, Lowpass, Switched-Capacitor Filters Features The MAX7409/MAX7410/MAX7413/MAX7414 5th-order, lowpass, switched-capacitor filters (SCFs) operate from a single +5V (MAX7409/MAX7410) or +3V (MAX7413/ MAX7414) supply. These devices draw only 1.2mA of supply current and allow corner frequencies from 1Hz to 15kHz, making them ideal for low-power post-DAC filtering and anti-aliasing applications. They feature a shutdown mode, which reduces the supply current to 0.2µA. ♦ 5th-Order Lowpass Filters Bessel Response (MAX7409/MAX7413) Butterworth Response (MAX7410/MAX7414) Two clocking options are available on these devices: self-clocking (through the use of an external capacitor) or external clocking for tighter corner-frequency control. An offset adjust pin allows for adjustment of the DC output level. ♦ Low Power 1.2mA (operating mode) 0.2µA (shutdown mode) The MAX7409/MAX7413 Bessel filters provide low overshoot and fast settling, while the MAX7410/MAX7414 Butterworth filters provide a maximally flat passband response. Their fixed response simplifies the design task to selecting a clock frequency. Applications ADC Anti-Aliasing CT2 Base Stations DAC Postfiltering Speech Processing Air-Bag Electronics Selector Guide PART OPERATING VOLTAGE (V) FILTER RESPONSE MAX7409 Bessel +5 MAX7410 Butterworth +5 MAX7413 Bessel +3 MAX7414 Butterworth +3 ♦ Clock-Tunable Corner Frequency (1Hz to 15kHz) ♦ Single-Supply Operation +5V (MAX7409/MAX7410) +3V (MAX7413/MAX7414) ♦ Available in 8-Pin µMAX/DIP Packages ♦ Low Output Offset: ±4mV Ordering Information PART TEMP. RANGE MAX7409CUA 0°C to +70°C 8 µMAX PIN-PACKAGE MAX7409CPA 0°C to +70°C 8 Plastic DIP MAX7409EUA MAX7409EPA MAX7410CUA -40°C to +85°C -40°C to +85°C 0°C to +70°C 8 µMAX 8 Plastic DIP 8 µMAX MAX7410CPA 0°C to +70°C 8 Plastic DIP MAX7410EUA MAX7410EPA -40°C to +85°C -40°C to +85°C 8 µMAX 8 Plastic DIP Ordering Information continued at end of data sheet. Typical Operating Circuit VSUPPLY Pin Configuration 0.1µF TOP VIEW VDD INPUT COM 1 8 CLK IN 2 7 SHDN GND 3 6 OS 5 OUT VDD 4 MAX7409 MAX7410 MAX7413 MAX7414 CLOCK IN CLK SHDN OUT MAX7409 MAX7410 MAX7413 MAX7414 GND OUTPUT COM OS 0.1µF µMAX/DIP ________________________________________________________________ Maxim Integrated Products 1 For free samples & the latest literature: http://www.maxim-ic.com, or phone 1-800-998-8800. For small orders, phone 408-737-7600 ext. 3468. MAX7409/MAX7410/MAX7413/MAX7414 General Description MAX7409/MAX7410/MAX7413/MAX7414 5th-Order, Lowpass, Switched-Capacitor Filters ABSOLUTE MAXIMUM RATINGS VDD to GND ..............................................................-0.3V to +6V IN, OUT, COM, OS, CLK, SHDN ................-0.3V to (VDD + 0.3V) OUT Short-Circuit Duration...................................................1sec Continuous Power Dissipation (TA = +70°C) 8-Pin DIP (derate 9.09mW/°C above +70°C) ...............727mW 8-Pin µMAX (derate 4.1mW/°C above +70°C) .............330mW Operating Temperature Ranges MAX74 _ _C_A ...................................................0°C to +70°C MAX74 _ _E_A ................................................-40°C to +85°C Storage Temperature Range .............................-65°C to +160°C Lead Temperature (soldering, 10sec) .............................+300°C Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability. ELECTRICAL CHARACTERISTICS—MAX7409/MAX7410 (VDD = +5V, filter output measured at OUT, 10kΩ || 50pF load to GND at OUT, OS = COM, 0.1µF capacitor from COM to GND, SHDN = VDD, fCLK = 100kHz, TA = TMIN to TMAX, unless otherwise noted. Typical values are at TA = +25°C.) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS FILTER CHARACTERISTICS Corner Frequency Clock-to-Corner Ratio fc fCLK / fc (Note 1) 0.001 to 15 Clock-to-Corner Tempco 10 Output Voltage Range Output Offset Voltage 0.25 VOFFSET DC Insertion Gain with Output Offset Removed Total Harmonic Distortion plus Noise Offset Voltage Gain COM Voltage Range Input Voltage Range at OS Input Resistance at COM kHz 100:1 VIN = VCOM = VDD / 2 VCOM = VDD / 2 (Note 2) THD+N AOS VCOM VOS fIN = 200Hz, VIN = 4Vp-p, measurement bandwidth = 22kHz -0.2 ±25 mV 0 0.2 dB -85 MAX7410 -78 dB 1 V/V Input, COM externally driven 2.0 2.5 3.0 Output, COM unconnected 2.3 2.5 2.7 Input, OS externally driven RCOM 110 Clock Feedthrough V ±4 MAX7409 OS to OUT ppm/°C VDD - 0.25 V VCOM ±0.1 V 180 kΩ 5 mVp-p Resistive Output Load Drive RL 10 1 kΩ Maximum Capacitive Output Load Drive CL 50 500 pF Input Leakage Current at COM SHDN = GND, VCOM = 0 to VDD ±0.1 ±10 µA Input Leakage Current at OS VOS = 0 to VDD ±0.1 ±10 µA 30 38 kHz ±13.5 ±20 µA CLOCK Internal Oscillator Frequency fOSC COSC = 1000pF (Note 3) Clock Output Current (Internal Oscillator Mode) ICLK VCLK = 0 or 5V Clock Input High VIH Clock Input Low VIL 2 21 4.5 _______________________________________________________________________________________ V 0.5 V 5th-Order, Lowpass, Switched-Capacitor Filters (VDD = +5V, filter output measured at OUT, 10kΩ || 50pF load to GND at OUT, OS = COM, 0.1µF capacitor from COM to GND, SHDN = VDD, fCLK = 100kHz, TA = TMIN to TMAX, unless otherwise noted. Typical values are at TA = +25°C.) PARAMETER SYMBOL CONDITIONS MIN UNITS TYP MAX 5.5 V Operating mode, no load 1.2 1.5 mA 1 POWER REQUIREMENTS Supply Voltage VDD Supply Current IDD 4.5 Shutdown Current I SHDN SHDN = GND 0.2 Power-Supply Rejection Ratio PSRR IN = COM (Note 4) 70 µA dB SHUTDOWN SHDN Input High VSDH SHDN Input Low VSDL SHDN Input Leakage Current 4.5 V ±0.2 V SHDN = 0 to VDD 0.5 V ±10 µA ELECTRICAL CHARACTERISTICS—MAX7413/MAX7414 (VDD = +3V, filter output measured at OUT pin, 10kΩ || 50pF load to GND at OUT, OS = COM, 0.1µF capacitor from COM to GND, SHDN = VDD, fCLK = 100kHz, TA = TMIN to TMAX, unless otherwise noted. Typical values are at TA = +25°C.) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS FILTER CHARACTERISTICS Corner Frequency fC Clock-to-Corner Ratio (Note 1) 0.001 to 15 fCLK / fC 100:1 Clock-to-Corner Tempco 10 Output Voltage Range Output Offset Voltage 0.25 VOFFSET DC Insertion Gain with Output Offset Removed Total Harmonic Distortion plus Noise Offset Voltage Gain COM Voltage Range Input Voltage Range at OS Input Resistance at COM kHz VIN = VCOM = VDD / 2 VCOM = VDD / 2 (Note 2) THD+N AOS VCOM VOS fIN = 200Hz, VIN = 2.5Vp-p, measurement bandwidth = 22kHz -0.2 ±25 mV 0 +0.2 dB -83 MAX7414 -81 dB 1 Input, COM externally driven 1.4 Output, COM unconnected 1.4 Input, OS externally driven V ±4 MAX7413 OS to OUT ppm/°C VDD - 0.25 V/V 1.5 1.6 V 1.5 1.6 V VCOM ±0.1 V RCOM 110 180 kΩ 3 mVp-p Resistance Output Load Drive RL 10 1 kΩ Maximum Capacitive Output Load Drive CL 50 500 pF Clock Feedthrough Input Leakage Current at COM Input Leakage Current at OS SHDN = GND, VCOM = 0 to VDD VOS = 0 to VDD ±0.1 ±10 µA ±0.1 ±10 µA _______________________________________________________________________________________ 3 MAX7409/MAX7410/MAX7413/MAX7414 ELECTRICAL CHARACTERISTICS—MAX7409/MAX7410 MAX7409/MAX7410/MAX7413/MAX7414 5th-Order, Lowpass, Switched-Capacitor Filters ELECTRICAL CHARACTERISTICS—MAX7413/MAX7414 (continued) (VDD = +3V, filter output measured at OUT pin, 10kΩ || 50pF load to GND at OUT, OS = COM, 0.1µF capacitor from COM to GND, SHDN = VDD, fCLK = 100kHz, TA = TMIN to TMAX, unless otherwise noted. Typical values are at TA = +25°C.) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS 21 30 38 kHz ±13.5 ±20 µA CLOCK Internal Oscillator Frequency fOSC COSC = 1000pF (Note 3) Clock Output Current (Internal Oscillator Mode) ICLK VCLK = 0 or 3V Clock Input High VIH Clock Input Low VIL 2.5 V 0.5 V 3.6 V mA POWER REQUIREMENTS Supply Voltage Supply Current VDD IDD 2.7 Operating mode, no load 1.2 1.5 Shutdown Current I SHDN SHDN = GND 0.2 1 Power-Supply Rejection Ratio PSRR IN = COM (Note 4) 70 µA dB SHUTDOWN SHDN Input High VSDH SHDN Input Low VSDL SHDN Input Leakage Current 2.5 V SHDN= 0 to VDD V 0.2 0.5 V ±10 µA FILTER CHARACTERISTICS (VDD = +5V for MAX7409/MAX7410, VDD = +3V for MAX7413/MAX7414, filter output measured at OUT, 10kΩ || 50pF load to GND at OUT, SHDN = VDD, fCLK = 100kHz, TA = TMIN to TMAX, unless otherwise noted.) PARAMETER CONDITIONS MIN TYP -1 -0.74 MAX UNITS BESSEL FILTERS—MAX7409/MAX7413 fIN = 0.5fC Insertion Gain Relative to DC Gain fIN = fC -3.0 -2.4 fIN = 4fC -3.6 -41.0 -35 fIN = 7fC -64.3 -58 dB BUTTERWORTH FILTERS—MAX7410/MAX7414 Insertion Gain Relative to DC Gain fIN = 0.5fC -0.3 0 fIN = fC -3.6 -3.0 -2.4 fIN = 3fC -47.5 -43 fIN = 5fC -70 -65 dB Note 1: The maximum fC is defined as the clock frequency fCLK = 100 x fC at which the peak S / (THD+N) drops to 68dB with a sinusoidal input at 0.2fC. Note 2: DC insertion gain is defined as ∆VOUT / ∆VIN. Note 3: fOSC (kHz) ≅ 30 x 103 / COSC (pF). Note 4: PSRR is the change in output voltage from a VDD of 4.5V and a VDD of 5.5V. 4 _______________________________________________________________________________________ 5th-Order, Lowpass, Switched-Capacitor Filters (VDD = +5V for MAX7409/MAX7410, VDD = +3V for MAX7413/MAX7414, fCLK = 100kHz, SHDN = VDD, COM = OS = VDD / 2, TA = +25°C, unless otherwise noted.) MAX7410/MAX7414 FREQUENCY RESPONSE (BUTTERWORTH) fC = 1kHz 0 fC = 1kHz -0.8 -16 -20 -1.2 -30 -1.6 -32 -40 -2.0 -40 -50 -2.4 -48 -60 -3.0 -70 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 -3.2 0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 INPUT FREQUENCY (kHz) MAX7410/MAX7414 PASSBAND FREQUENCY RESPONSE (BUTTERWORTH) MAX7409/MAX7413 PHASE RESPONSE (BESSEL) MAX7410/MAX7414 PHASE RESPONSE (BUTTERWORTH) 0 fC = 1kHz PHASE SHIFT (DEGREES) 0 INPUT FREQUENCY (Hz) -0.5 -1.0 -1.5 -2.0 -2.5 -50 0 fC = 1kHz -50 PHASE SHIFT (DEGREES) fC = 1kHz MAX7409 toc04 0.5 0 102 204 306 408 510 612 714 816 918 1.02k INPUT FREQUENCY (kHz) MAX7409 toc05 0 -100 -150 -200 0 0.2 -200 -250 0.4 0.6 0.8 1.0 1.2 1.4 0 1.6 SUPPLY CURRENT vs. SUPPLY VOLTAGE MAX7409 toc07 1.19 1.18 1.17 0.4 0.6 0.8 1.0 1.2 1.4 1.6 Table A. THD+N vs. Input Signal Amplitude Plot Characteristics LABEL fIN (Hz) fC (kHz) fCLK (kHz) MEASUREMENT BANDWIDTH (kHz) A 200 1 100 22 B 1k 5 500 80 1.16 1.15 0.2 INPUT FREQUENCY (kHz) INPUT FREQUENCY (kHz) INPUT FREQUENCY (Hz) SUPPLY CURRENT (mA) -150 -350 -250 0 102 204 306 408 510 612 714 816 918 1.02k -100 -300 -3.0 -3.5 MAX7409 toc06 -24 GAIN (dB) -10 -56 GAIN (dB) 0 -0.4 -8 GAIN (dB) GAIN (dB) 10 MAX7409 toc02 fC = 1kHz 0 MAX7409 toc01 8 MAX7409/MAX7413 PASSBAND FREQUENCY RESPONSE (BESSEL) MAX7409 toc03 MAX7409/MAX7413 FREQUENCY RESPONSE (BESSEL) 1.14 1.13 1.12 1.11 2.5 3.0 3.5 4.0 4.5 5.0 5.5 SUPPLY VOLTAGE (V) _______________________________________________________________________________________ 5 MAX7409/MAX7410/MAX7413/MAX7414 Typical Operating Characteristics Typical Operating Characteristics (continued) (VDD = +5V for MAX7409/MAX7410, VDD = +3V for MAX7413/MAX7414, fCLK = 100kHz, SHDN = VDD, COM = OS = VDD / 2, TA = +25°C, unless otherwise noted.) -20 -50 -60 B -70 -80 A -90 0 -40 -50 B -30 -40 -50 -60 -70 -70 -80 -80 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 B A A -90 0 0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 0.5 1.0 1.5 2.0 2.5 AMPLITUDE (Vp-p) AMPLITUDE (Vp-p) AMPLITUDE (Vp-p) MAX7414 TOTAL HARMONIC DISTORTION PLUS NOISE vs. INPUT SIGNAL AMPLITUDE SUPPLY CURRENT vs. TEMPERATURE INTERNAL OSCILLATOR PERIOD vs. SMALL CAPACITANCE SUPPLY CURENT (mA) -30 -40 -50 -60 1.16 1.15 1.14 1.13 B -70 VDD = +5V 1.17 A -90 0.5 1.0 1.5 2.0 3.0 VDD = +5V 80 VDD = +3V 60 40 VDD = +3V 0 -40 -20 0 20 40 60 80 0 100 500 1000 1500 2000 2500 3000 3500 CAPACITANCE (pF) INTERNAL OSCILLATOR PERIOD vs. LARGE CAPACITANCE INTERNAL OSCILLATOR FREQUENCY vs. SUPPLY VOLTAGE INTERNAL OSCILLATOR FREQUENCY vs. TEMPERATURE MAX7409 toc14 10 VDD = +5V 8 VDD = +3V 6 4 2 30.2 COSC = 1000pF 30.1 30.0 29.9 29.8 29.7 29.6 29.5 29.4 0 50 100 150 200 250 CAPACITANCE (nF) 300 350 OSCILLATOR FREQUENCY FREQUENCY (kHz) TEMPERATURE (°C) MAX7409 toc15 AMPLITUDE (Vp-p) 12 0 100 1.11 2.5 OSCILLATOR FREQUENCY (kHz) 0 120 20 1.12 -80 3.0 MAX7409 toc13 -20 1.18 OSCILLATOR PERIOD (µs) SEE TABLE A MAX7409 toc12 1.19 MAX7409 toc11 0 THD + NOISE (dB) -20 -90 -10 6 -30 -60 SEE TABLE A -10 THD + NOISE (dB) THD + NOISE (dB) -40 MAX7409 toc10 SEE TABLE A -10 -20 -30 0 MAX7409 toc09 SEE TABLE A THD + NOISE (dB) 0 MAX7409 toc08 0 -10 MAX7413 TOTAL HARMONIC DISTORTION PLUS NOISE vs. INPUT SIGNAL AMPLITUDE MAX7410 TOTAL HARMONIC DISTORTION PLUS NOISE vs. INPUT SIGNAL AMPLITUDE 31.5 COSC = 1000pF 31.0 30.5 MAX7409 toc16 MAX7409 TOTAL HARMONIC DISTORTION PLUS NOISE vs. INPUT SIGNAL AMPLITUDE OSCILLATOR PERIOD (ms) MAX7409/MAX7410/MAX7413/MAX7414 5th-Order, Lowpass, Switched-Capacitor Filters VDD = +3V 30.0 29.5 VDD = +5V 29.0 2.5 3.0 3.5 4.0 4.5 SUPPLY VOLTAGE (V) 5.0 5.5 -40 -20 0 20 40 60 TEMPERATURE (°C) _______________________________________________________________________________________ 80 100 5th-Order, Lowpass, Switched-Capacitor Filters (VDD = +5V for MAX7409/MAX7410, VDD = +3V for MAX7413/MAX7414, fCLK = 100kHz, SHDN = VDD, COM = OS = VDD / 2, TA = +25°C, unless otherwise noted.) OUTPUT OFFSET VOLTAGE vs. SUPPLY VOLTAGE OUTPUT OFFSET VOLTAGE vs. TEMPERATURE VDD = +3V -3.50 -3.75 VDD = +5V -4.00 MAX7409 toc18 -2.5 DC OFFSET VOLTAGE (mV) -3.25 OFFSET VOLTAGE (mV) -2.0 MAX7409 toc17 -3.00 -3.0 -3.5 -4.0 -4.5 -4.25 -5.0 -4.50 -40 -20 0 20 40 60 80 2.5 100 3.0 3.5 4.0 4.5 5.0 5.5 SUPPLY VOLTAGE (V) TEMPERATURE (°C) Pin Description PIN NAME FUNCTION 1 COM 2 IN 3 GND Ground 4 VDD Positive Supply Input: +5V for MAX7409/MAX7410, +3V for MAX7413/MAX7414. 5 OUT Filter Output 6 OS 7 SHDN 8 CLK Common Input Pin. Biased internally at midsupply. Bypass COM externally to GND with a 0.1µF capacitor. To override internal biasing, drive COM with an external supply. Filter Input Offset Adjust Input. To adjust output offset, connect OS to an external supply through a resistive voltagedivider (Figure 3). Connect OS to COM if no offset adjustment is needed. Refer to the Offset and CommonMode Input Adjustment section. Shutdown Input. Drive low to enable shutdown mode; drive high or connect to VDD for normal operation. Clock Input. Connect an external capacitor (COSC) from CLK to ground: fOSC (kHz) = 30 x 103 / COSC (pF). To override the internal oscillator, connect CLK to an external clock: fC = fCLK /100. _______________Detailed Description The MAX7409/MAX7413 Bessel filters provide low overshoot and fast settling responses, and the MAX7410/ MAX7414 Butterworth filters provide a maximally flat passband response. All parts operate with a 100:1 clock-to-corner frequency ratio and a 15kHz maximum corner frequency. Bessel Characteristics Lowpass Bessel filters such as the MAX7409/MAX7413 delay all frequency components equally, preserving the shape of step inputs (subject to the attenuation of the higher frequencies). Bessel filters settle quickly—an important characteristic in applications that use a multiplexer (mux) to select an input signal for an analog-todigital converter (ADC). An anti-aliasing filter placed between the mux and the ADC must settle quickly after a new channel is selected. Butterworth Characteristics Lowpass Butterworth filters such as the MAX7410/ MAX7414 provide a maximally flat passband response, making them ideal for instrumentation applications that require minimum deviation from the DC gain throughout the passband. _______________________________________________________________________________________ 7 MAX7409/MAX7410/MAX7413/MAX7414 Typical Operating Characteristics (continued) MAX7409/MAX7410/MAX7413/MAX7414 5th-Order, Lowpass, Switched-Capacitor Filters RS 2V/div + - VIN L2 C1 L4 C3 C5 RL A 2V/div B 2V/div Figure 2. 5th-Order Ladder Filter Network C Clock Signal 200µs/div A: 1kHz INPUT SIGNAL B: MAX7409 BESSEL FILTER RESPONSE; fC = 5kHz C: MAX7410 BUTTERWORTH FILTER RESPONSE; fC = 5kHz Figure 1. Bessel vs. Butterworth Filter Response The difference between Bessel and Butterworth filters can be observed when a 1kHz square wave is applied to the filter input (Figure 1, trace A). With the filter cutoff frequencies set at 5kHz, trace B shows the Bessel filter response and trace C shows the Butterworth filter response. Background Information Most switched-capacitor filters (SCFs) are designed with biquadratic sections. Each section implements two filtering poles, and the sections are cascaded to produce higher-order filters. The advantage to this approach is ease of design. However, this type of design is highly sensitive to component variations if any section’s Q is high. An alternative approach is to emulate a passive network using switched-capacitor integrators with summing and scaling. Figure 2 shows a basic 5th-order ladder filter structure. A switched-capacitor filter such as the MAX7409/ MAX7410/MAX7413/MAX7414 emulates a passive ladder filter. The filter’s component sensitivity is low when compared to a cascaded biquad design, because each component affects the entire filter shape, not just one pole-zero pair. In other words, a mismatched component in a biquad design will have a concentrated error on its respective poles, while the same mismatch in a ladder filter design results in an error distributed over all poles. External Clock The MAX7409/MAX7410/MAX7413/MAX7414 family of SCFs is designed for use with external clocks that have a 50% ±10% duty cycle. When using an external clock with these devices, drive CLK with a CMOS gate powered from 0 to VDD. Varying the rate of the external clock adjusts the corner frequency of the filter as follows: fC = fCLK / 100 Internal Clock When using the internal oscillator, connect a capacitor (C OSC) between CLK and ground. The value of the capacitor determines the oscillator frequency as follows: fOSC (kHz) = 30 x 103/ COSC (pF) Minimize the stray capacitance at CLK so that it does not affect the internal oscillator frequency. Vary the rate of the internal oscillator to adjust the filter’s corner frequency by a 100:1 clock-to-corner frequency ratio. For example, an internal oscillator frequency of 100kHz produces a nominal corner frequency of 1kHz. Input Impedance vs. Clock Frequencies The MAX7409/MAX7410/MAX7413/MAX7414’s input impedance is effectively that of a switched-capacitor resistor (see the following equation), and is inversely proportional to frequency. The input impedance values determined below represent the average input impedance, since the input current is not continuous. As a rule, use a driver with an output impedance less than 10% of the filter’s input impedance. Estimate the input impedance of the filter using the following formula: ZIN = 1 / ( fCLK x 2.1pF) For example, an fCLK of 100kHz results in an input impedance of 4.8MΩ. 8 _______________________________________________________________________________________ 5th-Order, Lowpass, Switched-Capacitor Filters VSUPPLY 0.1µF VDD INPUT __________Applications Information SHDN OUT IN OUTPUT COM 0.1µF MAX7409 MAX7410 MAX7413 MAX7414 Offset and Common-Mode Input Adjustment The COM pin sets the common-mode input voltage and is biased at mid-supply with an internal resistor-divider. If the application does not require offset adjustment, connect OS to COM. For applications requiring offset adjustment, apply an external bias voltage through a resistor-divider network to OS such as shown in Figure 3. For applications that require DC level shifting, adjust OS with respect to COM. (Note: OS should not be left unconnected.) The output voltage is represented by this equation: MAX7409/MAX7410/MAX7413/MAX7414 Low-Power Shutdown Mode These devices feature a shutdown mode that is activated by driving SHDN low. In shutdown mode, the filter’s supply current reduces to 0.2µA and its output becomes high impedance. For normal operation, drive SHDN high or connect it to VDD. CLOCK CLK 50k 50k OS 0.1µF 50k GND Figure 3. Offset Adjustment Circuit V+ VOUT = (VIN - VCOM) + VOS with VCOM = VDD / 2 (typical), and where (VIN - VCOM) is lowpass filtered by the SCF, and OS is added at the output stage. See the Electrical Characteristics for the voltage range of COM and OS. Changing the voltage on COM or OS significantly from midsupply reduces the filter’s dynamic range. VDD OUT INPUT V+ V- Power Supplies The MAX7409/MAX7410 operate from a single +5V supply and the MAX7413/MAX7414 operate from a single +3V supply. Bypass V DD to GND with a 0.1µF capacitor. If dual supplies are required (±2.5V for MAX7409/MAX7410, ±1.5V for MAX7413/MAX7414), connect COM to system ground and connect GND to the negative supply. Figure 4 shows an example of dual-supply operation. Single- and dual-supply performance are equivalent. For either single- or dual-supply operation, drive CLK and SHDN from GND (V- in dualsupply operation) to VDD. For ±5V dual-supply applications, use the MAX291–MAX297. Input Signal Amplitude Range The optimal input signal range is determined by observing the voltage level at which the Total Harmonic Distortion + Noise is minimized for a given corner frequency. The Typical Operating Characteristics show graphs of the devices’ Total Harmonic Distortion plus Noise Response as the input signal’s peak-to-peak amplitude is varied. SHDN CLOCK IN CLK * OUTPUT COM MAX7409 MAX7410 MAX7413 MAX7414 OS 0.1µF 0.1µF GND V*DRIVE SHDN TO V- FOR LOW-POWER SHUTDOWN MODE. Figure 4. Dual-Supply Operation Anti-Aliasing and DAC Postfiltering When using these devices for anti-aliasing or DAC postfiltering, synchronize the DAC (or ADC) and the filter clocks. If the clocks are not synchronized, beat frequencies will alias into the desired passband. Harmonic Distortion Harmonic distortion arises from nonlinearities within the filter. These nonlinearities generate harmonics when a pure sine wave is applied to the filter input. Table 1 lists typical harmonic-distortion values for the MAX7410/ MAX7414 with a 10kΩ load at TA = +25°C. Table 2 lists typical harmonic-distortion values for the MAX7409/ MAX7413 with a 10kΩ load at TA = +25°C. _______________________________________________________________________________________ 9 MAX7409/MAX7410/MAX7413/MAX7414 5th-Order, Lowpass, Switched-Capacitor Filters Table 1. MAX7410/MAX7414 Typical Harmonic Distortion FILTER fCLK (kHz) fIN (Hz) 500 1k 100 200 500 1k MAX7410 VIN (Vp-p) TYPICAL HARMONIC DISTORTION (dB) 2nd 3rd 4th -85 -67 -86.7 -82 -84 -78 -88.7 -88.5 -85.3 -74 -87.1 -87.6 -86.1 -85.5 -85.8 -86.4 5th 4 MAX7414 2 100 200 Table 2. MAX7409/MAX7413 Typical Harmonic Distortion FILTER fCLK (kHz) fIN (Hz) 500 1k MAX7409 TYPICAL HARMONIC DISTORTION (dB) 2nd 3rd 4th 5th -82.5 -79 -88.8 -91.1 -83.5 -85.4 -88.4 -88.8 -86 -81 -87.3 -87.9 -86.4 -86.9 -87.9 -88.3 4 100 200 500 1k MAX7413 2 100 200 Ordering Information (continued) PART TEMP. RANGE MAX7413CUA 0°C to +70°C 8 µMAX MAX7413CPA 0°C to +70°C 8 Plastic DIP MAX7413EUA MAX7413EPA -40°C to +85°C -40°C to +85°C 8 µMAX 8 Plastic DIP MAX7414CUA 0°C to +70°C 8 µMAX MAX7414CPA 0°C to +70°C 8 Plastic DIP MAX7414EUA -40°C to +85°C 8 µMAX MAX7414EPA -40°C to +85°C 8 Plastic DIP 10 VIN (Vp-p) PIN-PACKAGE Chip Information TRANSISTOR COUNT: 1457 ______________________________________________________________________________________ 5th-Order, Lowpass, Switched-Capacitor Filters 8LUMAXD.EPS ______________________________________________________________________________________ 11 MAX7409/MAX7410/MAX7413/MAX7414 ________________________________________________________Package Information 5th-Order, Lowpass, Switched-Capacitor Filters PDIPN.EPS MAX7409/MAX7410/MAX7413/MAX7414 Package Information (continued) Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are implied. Maxim reserves the right to change the circuitry and specifications without notice at any time. 12 ____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 © 1998 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.