Rainbow-electronics MAX7480 Manual de usuario descargar pdf (Pagina 8)

MAX7480

8th-Order, Lowpass, Butterworth,

Switched-Capacitor Filter

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.

_____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600

Anti-Aliasing and Post-DAC Filtering

When using the MAX7480 for anti-aliasing or post-DAC

filtering, synchronize the DAC and the filter clocks. If

the clocks are not synchronized, beat frequencies may

alias into the passband.

The high clock-to-corner frequency ratio (100:1) also

eases the requirements of pre- and post-SCF filtering.

At the input, a lowpass filter prevents the aliasing of fre-

quencies around the clock frequency into the pass-

band. At the output, a lowpass filter attenuates the

clock feedthrough.

A high clock to corner-frequency ratio allows a simple

RC lowpass filter, with the cutoff frequency set above

the SCF corner frequency to provide input anti-aliasing

and reasonable output clock attenuation.

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

the MAX7480’s typical harmonic-distortion values with

a 10kΩ load at T

= +25°C.

V+ = +2.5V

V- = -2.5V

CLK

GND

INPUT

OUTPUTOUT

0.1µF

CLOCK

*DRIVE SHDN TO V- FOR LOW-POWER SHUTDOWN MODE.

SHDN

COM

0.1µF

MAX7480

V+

V-

Figure 4. Dual-Supply Operation

5th

3rd

-89-68

-93-73

200

100

CLK

(kHz)

4th

2nd

-85

-91

TYPICAL HARMONIC DISTORTION (dB)

-82

-89

MAX7480

(Vp-p)

(kHz)

FILTER

400

200

(Hz)

Table 1. Typical Harmonic Distortion

TRANSISTOR COUNT: 1116

Chip Information

1 2 3 4 5 6 7 8

Switched-Capacitor Filter 1

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