of Microprocessors

DIGITAL-TO-ANALOG AND ANALOG-TO-DIGITAL CONVERTERS 249
10 kn 10 kn
10 kn
u
V,ef
N
ANY
VOLTAGE 20kn 20 kn 20 kn
BETWEEN
-10 AND
+/OV
eee
20 kn 1.20 kn
1 LJ-1---±b~Ioutllout 2
FEEDBACK
JOkn
Fig. 7-20. 7530-type 10-bit IC DAC
By far the most important feature of this circuit is its ability to handle
bipolar reference inputs. In fact, there is nothing to prevent audio signals up
to 10 V in amplitude from being applied to the reference input. The two
output buses are complements of each other. With all switches in the zero
state (shown), the entire reference current (less lLSB) is directed to the lout2
bus and none goes to loutl. The converse is true for all switches in the one
state. In the intermediate states, the sum of the two currents equals the
reference current less lLSB. Thus, if the input, D, is considered to be an
>- -OUTPUT
OUTPUT
(B)
'MATCHED TO 0.1%
Fig. 7-21. Applications of the 7530 10-bit DAC IC. (A) Digital potentiometer.
(8) Four-quadrant multiplying DAC.