Rainbow Electronics MAX1200 - Manual (Page 13)

MAX1200
+5V Single-Supply, 1Msps, 16-Bit
Self-Calibrating ADC
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The MAX1200 has three power-supply inputs: analog
V
DD (AV DD ), digital V DD (DV DD ), and drive V DD
(DRV
DD
). Each AV DD input should be decoupled with
parallel ceramic chip capacitors of values 0.1µF and
0.001µF, with these capacitors as close to the pin as
possible and with the shortest possible connection to
the ground plane. The DV
DD pins should also have
separate 0.1µF capacitors again adjacent to their
respective pins, as should the DRV
DD pin. Minimize the
digital load capacitance. However, if the total load
capacitance on each digital output exceeds 20pF, the
DRV
DD decoupling capacitor should be increased or,
preferably, digital buffers should be added.
The power-supply voltages should also be decoupled
with large tantalum or electrolytic capacitors at the
point they enter the PCB. Ferrite beads with additional
decoupling capacitors forming a pi network may
improve performance.
The analog power-supply input (AV DD ) for the
MAX1200 is typically +5V while the digital supplies can
vary from +3V to +5V. Usually, DV
DD and DRV DD pins
are connected to the same power supply. Note that the
DV
DD supply voltage must be greater than or equal to
the DRV DD voltage. For example, a digital +3.3V sup-
ply could be connected to DRV DD while a cleaner +5V
supply is connected to DV DD , resulting in slightly
improved performance. Alternatively, the +3.3V supply
could be connected to both DRV
DD and DV DD .
However, the +3.3V supply must not be connected to
DV DD while the +5V supply is connected to DRV DD
(Table 2).
Table 2. Power-Supply Voltage
Combinations
Chip Information
TRANSISTOR COUNT: 56,577
SUBSTRATE CONNECTED TO AGND
AV DD
(V)
DV DD
(V)
DRV DD
(V)
ALLOWED/
NOT ALLOWED
+5 +5 +5 Allowed
+5 +5 +3.3 Allowed
+5 +3.3 +3.3 Allowed
+5 +3.3 +5
Not
Allowed