DAC8SPEC.TXT 8 BIT DIGITAL TO ANALOG COVERTER ---------------------------------------------- The DAC8 card is a 2 channel 8-bit Multiplying Digital to Analog Converter. Typical applications include servo, programmable power supply, sound card, variable gain amplifier, etc.. Maximum sample rate is 44 khz. Both channels have sharp cutoff low-pass filters for signal conditioning and noise reduction. A 2.5 volt voltage reference is available for use with external circuitry. The voltage range is 0 to -2.5v when DAC outputs are used directly (filter bypassed). When filter outputs are used voltage will be 0 to 5v. These ranges can be altered with external resistive dividers or amplifiers. Output voltage is determined by the value written to each channel. The lowest value occurs when 00h is written and the highest with FFh. Dual sharp-cutoff active filters improve playback quality of stereo audio and provide overshoot damping in control applications. The cutoff frequency is approximately 4hkz and they have a gain of 2. These filters can be used independently from the DAC circuit. This means they can be used to improve record quality when switched to ADC inputs if one is installed. A single filter with extremely sharp cutoff and a gain of 4 can be implemented by placing the two filters in tandem. External electrolytic capacitors might be used on the filter inputs to decouple DC offsets. SPECIFICATIONS -------------- Resolution: 0.39% Full Scale Filter output impedance: 220ohm (drives speaker/phones 60 ohms or greater) Block Diagram: PC BUS : ,--DAC A IN ,----0 to -2.5V DAC A OUT : ,----, : : : :2.5v; J11 J16 : ,------, : ,------, : :VREF;---o---o-----: DAC : : J9 J10 : FILT : : '----' : : CH A :-----o--o-----: A :---0 to 5V FILT A OUT :-------- : ----------: : : '------' : : '------' : : : '--------- FILT A IN : : : : ,---DAC B IN ,---0 to -2.5V DAC B OUT : : : : : : J12 : ,------, : ,------, : '---o-------: DAC : : J14 J15 : FILT : : : CH B :-----o--o-----: B :---0 to 5V FILT B OUT :---------------------: : : '------' : '------' : : '--------- FILT B IN I/O Connector pinout: 1 Ground 2 DAC A in 3 Ground 4 DAC B in 5 Ground 6 DAC A out Registers: 7 Ground 8 DAC B out DAC Chan A (out) = 262h* 9 Ground 10 Filter A in DAC Chan B (out) = 263h* 11 Filter B in 12 Filter A out 13 Filter B out 14 NC 15 NC 16 NC 17 NC 18 NC 19 NC 20 NC 21 NC 22 NC Address Jumpers: 23 NC 24 NC J1 J2 J3 J4 162-163=1-5 2-6 3-7 4-8 25 Ground 26 NC o o o o 1A2-1A3=1-6 2-5 3-7 4-8 27 Ground 28 +5v out o o o o 262-263=1-5 2-6 3-8 4-7* 29 Ground 30 +2.5 vref out J5 J6 J7 J8 2A2-2A3=1-6 2-5 3-8 4-7 31 Ground 32 -12v out 322-323=1-8 2-6 3-7 4-5 33 Ground 34 +12v out *default The DAC8 is often used with inexpensive PC motherboards and the MVS ROM Drive for embedded applications or portable computers. Using a right angle Passive Backplane (part number PB4) allows the cards to lie down flat. Everything can now fit into a compact low-profile case. The DAC8 has the same form factor as the MVS Single Board Computer. Corner holes are in the same position which simplifies mounting with standoffs. The PC Bus ends of the DAC8 and the SBC are connected with a passive backplane. This is constructed using 62 pin IDC connectors (part number MVCON1) and a short length of ribbon cable. Other PC adapter cards can be added on in the same way. LIMITED WARRANTY MVS will repair free of charge product suffering from manufacturing defects for a period of 5 years after shipping. This will be done only if it has been determined by MVS that the product has not been misused (improper voltages, physical alteration, etc.). Otherwise a minimum service charge is required. In either case it is necessary to contact MVS for a Returned Merchandise Authorization (RMA) number before shipping the unit.