MAX125_08 Datasheet, PDF (13/15 Pages) Maxim Integrated Products – 2x4-Channel, Simultaneous-Sampling 14-Bit DAS

2x4-Channel, Simultaneous-Sampling
14-Bit DAS
EXTERNAL
SETPOINTS
CONTROLLER
MAIN DC
POWER
STAGE
AACC
MMOOTTOORR
RESOLVER/
ENCODER
R/E
DSP
µC
14
MAX125
MAX126
14 BIT ADC +
MICRO-
SEQUENCER
A
CH1 ^B
A
CH2 B
A
CH3 _B
A
CH4 _B
AUX
MAIN DC
TEMP
VELOCITY
FEEDBACK
Figure 10. Vector Motor Control
brought to the MAX125/MAX126 at CH4B. The addi-
tional channels can be used to evaluate slower analog
inputs, such as the main DC bus voltage (CH2B), tem-
perature sensors (CH3B), or other analog inputs (AUX,
CH1B).
Power-Supply Bypassing
and Ground Management
For optimum system performance, use printed circuit
boards with separate analog and digital ground
planes. Wire-wrapped boards are not recommended.
Connect the two ground planes together at the low-
impedance power-supply source. Connect DGND and
AGND together at the IC. For the best ground connec-
tion, connect the DGND and AGND pins together and
connect that point to the system analog ground plane
to avoid interference from other digital noise sources. If
DGND is connected to the system digital ground, digi-
tal noise may get through to the ADC’s analog portion.
The AGND pins must be connected directly to a low-
impedance ground plane. Extra impedance between
the pins and the ground plane increases crosstalk and
degrades INL.
Bypass AV_DD and AV_SS with 0.1µF ceramic capacitors
to AGND. Mount them with short leads close to the
device. Ferrite beads may also be used to further iso-
late the analog and digital power supplies. Bypass
DV_DD with a 0.1µF ceramic capacitor to DGND.
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