ZIRCON-MM
User Manual v2.11 © 2002 Diamond Systems Corporation P. 15
11. ANALOG I/O
Zircon-MM contains an 8-bit resolution A/D converter and an 8-bit resolution D/A converter on a
single chip. The A/D converter input is fed by an 8 channel analog input multiplexor to expand the
number of input channels to 8 single-ended analog voltage inputs. The D/A converter is
nonmultiplexed, providing a single analog voltage output.
The A/D and D/A converter chip is factory calibrated for accuracy, and no user trims are provided (or
available). Zircon-MM therefore requires no calibration over its entire operating lifetime.
The analog I/O can be set to several different ranges, depending on the model of Zircon-MM. For
model ZMM-LC, the analog circuitry is powered from the 5/Ground supplies, so all analog
I/O is limited to positive voltages (0 - 2.5V or 0 - 1.25V ranges). On ZMM-DX, the analog circuitry is
powered by an on-board DC/DC converter that provides ded5/-5 supplies to the board. Using
these supplies bipolar input and output ranges are available, inc/-2.5V and +/-1.25V.
In addition, on ZMM-DX the input impedance is improved by the addition of a precision op amp
between the input multiplexor and the A/D converter. The addition of this op amp further enables the
use of a voltage divider network to provide two additional input ranges: +/-5V and 0-5V. The voltage
divider network, however, has the side effect of reducing the input impedance of the analog input
channels.
On ZMM-LC, the D/A converter is unbuffered and directly drives the output pin on the user I/O
header. This output can develop up to 1.25mA of current across a 2K
Ω
load (at a maximum output
voltage of 2.5V). On ZMM-DX, the output is buffered through an op amp as described above,
providing up to 30mA of drive current capability.
