Specifications

Motor Control
Monitoring and controlling multichannel currents and voltages
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Overview
To monitor and control a motor,
multiple currents and voltages
need to be measured and the phase
integrity between the channels
preserved. Designers are faced
with two choices for the ADC
architecture: use multiple single-
channel ADCs in parallel, a design
that makes it very difficult to synch
up the conversion timing; or use a
simultaneous-sampling ADC. The
simultaneous-sampling architecture
uses either multiple ADCs in a single
package, all with a single conversion
trigger, or with multiple sample-
and-hold amplifiers (also referred
to as track-and-hold amplifiers) on
the analog inputs. In the case of
multiple sample-and-hold amplifiers,
a multiplexer is still used between
the multiple analog inputs and the
single ADC. Simultaneous sampling
eliminates the need for complicated
digital-signal-processing algorithms.
Sampling speeds of 100ksps or more
are common for motor-control appli-
cations. At these speeds the ADC
continuously monitors the motor for
any indication of errors or potential
damage. At the first sign of trouble,
the system can correct itself or shut
down when necessary. If the ADC
does not sample fast enough, an
error condition might not be identi-
fied early enough to be addressed.
The amount of dynamic measurement
range varies for each motor-control
application. In some cases 12 bits
of resolution are sufficient. For
the more precise motor-control
applications, however, 16 bits of
resolution are a more common
standard. A high-performance
16-bit ADC like the MAX11044 or
MAX11049 allows a system to achieve
better than 90dB of dynamic range.
Maxim offers a broad portfolio
of simultaneous-sampling ADCs
designed for motor control. Devices
have both serial and parallel inter-
faces, and 12-, 14-, or 16-bit operation.
Monitoring and controlling multichannel currents and voltages