AD664 Analog Devices, AD664 Datasheet - Page 19

• Manufacturer Part Number: AD664
• Description: Monolithic 12-Bit Quad DAC
• Manufacturer: Analog Devices

Specifications of AD664

• Resolution (bits): 12bit
• Dac Update Rate: 125kSPS
• Dac Settling Time: 8µs
• Max Pos Supply (v): +16.5V
• Single-supply: No
• Dac Type: Voltage Out
• Dac Input Format: Byte,Nibble,Par

REV.
APPLICATIONS OF THE AD664
“Tester-Per-Pin” ATE Architecture
Figure 29 shows the AD664 used in a single channel of a digital
test system. In this scheme, the AD664 supplies four individual
output voltages. Two are provided to the V
puts of the AD345 pin driver I.C. to set the digital output levels.
Two others are routed to the inputs of the AD96687 dual com-
parator to supply reference levels of the readback features. This
approach can be replicated to give as many channels of stimulus/
readback as the tester has pins. The AD664 is a particularly
appropriate choice for a large-scale system because the low
power requirements (under 500 mW) ease power supply and
cooling requirements. Analog ground currents of 600 A or less
make the ground current management task simpler. All DACs
can be driven from the same system reference and will track
over time and temperature. Finally, the small board area
required by the AD664 (and AD345 and AD96687) allows a
high functional density.
X-Y Plotters
Figure 30 is a block diagram of the control section of a
microprocessor-controlled X-Y pen plotter. In this conceptual
exercise, two of the DACs are used for the X-channel drive and
two are used for the Y-channel drive. Each provides either the
coarse or fine movement control for its respective channel. This
approach offers increased resolution over some other approaches.
A designer can take advantage of the reset feature of the AD664
in the following manner. If the system is designed such that the
“HOME” position of the pen (or galvanometer, beam, head or
similar mechanism) results when the outputs of all of the DACs
are at zero, then no system software is required to home the
pen. A simple reset signal is sufficient.
Similarly, the transparent feature could be used to the same
end. One code can be sent to all DACs at the same time to send
the pen to the home position. Of course, this would require
D
Figure 29. AD664 in “Tester-per-Pin” Architecture
HIGH
and V
LOW
in-
–19–
some software where the previous example would require only a
single reset strobe signal!
Drawing scaling can be achieved by taking advantage of the
AD664’s software programmable gain settings. If, for example,
an “A” size drawing is created with gain settings of 1, then a
“C” size drawing can be created by simply resetting all DAC
gains to 2 and redrawing the object. Conversely, a “C” size
drawing created with gains of 2 can be reduced to “A” size sim-
ply by changing the gains to 1 and redrawing. The same princi-
pal applies for conversion from “B” size to “D” size or “D” size
to “B” size. The multiplying capability of the AD664 provides
another scaling option. Changing the reference voltage provides
a proportional change in drawing size. Inverting the reference
voltage would invert the drawing.
Swapping digital input data from the X channel to the Y chan-
nel would rotate the drawing 90 degrees.
Figure 30. X-Y Plotter Block Diagram
AD664