Rainbow-electronics MAX2108 Manual de usuario descargar pdf (Pagina 7)

MAX2108

Direct-Conversion Tuner IC

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Power-Supply Sequencing

The MAX2108 has several +5V supply pins. Configure

the supply layout in a star format, with a bypass capac-

itor that dominates the rise time of the supply at the

center of the star to ensure that all pins see approxi-

mately the same voltage during power-up.

Filters in Direct-Conversion Tuners

Typically, a 5th- or 7th-order L-C lowpass filter is used

for anti-aliasing the ADCs following the MAX2108.

Table 1 offers suggested component values for these

lowpass filters. Figures 1 and 2 describe typical filtering

requirements.

Table 1. Suggested Component Values for Discrete Lowpass Filters

0.1dB Chebyshev,

= 30MHz

0.1dB Chebyshev,

= 20MHz

FILTER TYPE

ADC

SAMPLING

RATE

(Msps)

(Ω)

(pF)

620

910

(nH)

(pF)

910

1500

(nH)

(pF)

1000

1500

(nH)

(pF)

(kΩ)

50 15 680 39 820 33 Short Open 20

0.1dB Chebyshev,

= 20MHz

50 9 390 28 620 34 680 28 20

0.1dB Chebyshev,

= 45MHz

1 2 3 4 5 6 7 8 9 10 11 12

Direct-Conversion Tuner IC 1

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Rainbow-electronics MAX2108 Manual de usuario Pagina 7

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