Rainbow Electronics MAX2105 - Manual (Page 14)

MAX2102/MAX2105
Power-Supply Sequencing
The MAX2102/MAX2105 have several +5V supply pins.
The supply layout should be in a star format, with a
bypass capacitor that dominates the rise time of the
supply at the center of the star, to ensure that all pins
see approximately the same voltage during power-up.
The prescaler V CC (pin 28) must be connected to the
same V CC as the other V CC pins, even if the prescaler
is not used. Leaving PSGND open will disable the
prescaler function and, in this state, the prescaler will
not dissipate any power.
Systems Consideration: Lowpass Filters in
Direct-Conversion Tuners
Typically, a 5th or 7th-order L-C lowpass filter is used
for anti-aliasing the ADCs following the MAX2102.
Figures 4 and 5 describe typical filtering requirements.
Table 1 offers suggested component values for these
lowpass filters.
Chip Information
TRANSISTOR COUNT: 1852
SUBSTRATE CONNECTED TO GND
Direct-Conversion Tuner ICs for
Digital DBS Applications
14 ______________________________________________________________________________________
Q
I
“1” “2” “3” “4”
MATCHED FILTERS
DIGITAL SIGNAL PROCESSING
ANALOG LP FILTERS ADCs
MAX2102
MAX2105
Figure 4. I, Q Signal Path