AD7845 Analog Devices, AD7845 Datasheet - Page 11

• Manufacturer Part Number: AD7845
• Description: Complete 12-Bit CMOS Multiplying DAC
• Manufacturer: Analog Devices

Specifications of AD7845

• Resolution (bits): 12bit
• Dac Update Rate: 200kSPS
• Dac Settling Time: 5µs
• Max Pos Supply (v): +15.75V
• Single-supply: No
• Dac Type: Voltage Out
• Dac Input Format: Par

REV. B
Figure 23 and 24 are the interface circuits for the Z80 and
MC6809 microprocessors. Again, these use the same basic
format as the 8085A interface.
Figure 23. AD7845 to Z80 Interface
Figure 24. MC6809 Interface
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DIGITAL FEEDTHROUGH
In the preceding interface configurations, most digital inputs to
the AD7845 are directly connected to the microprocessor bus.
Even when the device is not selected, these inputs will be con-
stantly changing. The high frequency logic activity on the bus
can feed through the DAC package capacitance to show up as
noise on the analog output. To minimize this digital feedthrough
isolate the DAC from the noise source. Figure 25 shows an
interface circuit which uses this technique. All data inputs are
latched from the busy by the CS signal. One may also use other
means, such as peripheral interface devices, to reduce the digital
feedthrough.
Figure 25. AD7845 Interface Circuit Using Latches to
Minimize Digital Feedthrough
AD7845