Chip information, Package information, Table 2. power-supply voltage combinations – Rainbow Electronics MAX1205 User Manual

Page 12

MAX1205

+5V Single-Supply, 1Msps, 14-Bit
Self-Calibrating ADC

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implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.

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is a registered trademark of Maxim Integrated Products.

First, a multilayer printed circuit board (PCB) with sepa-
rate ground and power-supply planes is recommend-
ed. Run high-speed signal traces directly above the
ground plane. Since the MAX1205 has separate analog
and digital ground buses (AGND and DGND respec-
tively), the PCB should also have separate analog and
digital ground sections connected at only one point
(star ground). Digital signals should run above the digi-
tal ground plane and analog signals should run above
the analog ground plane. Digital signals should be kept
far away from the sensitive analog inputs, reference
inputs senses, common-mode input, and clock input.

The MAX1205 has three power-supply inputs: analog
V

(AV

), digital V

(DV

), and drive V

(DRV

Each AV

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

pins should also have separate 0.1µF

capacitors adjacent to their respective pins, as should the
DRV

pin. Minimize the digital load capacitance.

However, if the total load capacitance on each digital out-
put exceeds 20pF, the DRV

decoupling capacitor

should be increased or, preferably, digital buffers should
be added.

The power-supply voltages should 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

) for the

MAX1205 is typically +5V while the digital supplies can
vary from +5V to +3V. Usually, DV

and DRV

pins

are connected to the same power supply. Note that the
DV

supply voltage must be greater than or equal to

the DRV

voltage. For example, a digital +3.3V supply

could be connected to DRV

while a cleaner +5V

supply is connected to DV

, resulting in slightly

improved performance. Alternatively, the +3.3V supply
could be connected to both DRV

and DV

However, the +3.3V supply should not be connected to
DV

while the +5V supply is connected to DRV

(Table 2).

Table 2. Power-Supply Voltage Combinations

___________________Chip Information

TRANSISTOR COUNT: 56,577

SUBSTRATE CONNECTED TO: AGND

(V)

ALLOWED/NOT ALLOWED

Allowed

Not Allowed

Allowed

DRV

(V)

+3.3

(V)

+3.3

Package Information

MQFP44.EPS