DAC312BR/883 Analog Devices, DAC312BR/883 Datasheet - Page 13

• Manufacturer Part Number: DAC312BR/883
• Description: 12-Bit High Speed Multiplying D/A Converter
• Manufacturer: Analog Devices

DAC312
DESCRIPTION OF OPERATION
The DAC312 is divided into two major sections, an 8 segment
generator and a 9-bit master/slave D/A converter. In operation
the device performs as follows (see Simplified Schematic).
The three most significant bits (MSBs) are inputs to a 3-to-8
line decoder. The selected resistor (R5 in the figure) is con-
nected to the master/slave 9-bit D/A converter. All lower order
resistors (R1 through R4) are summed into the I
line, while all
O
higher order resistors (R6 through R8) are summed into the I
O
line. The R5 current supplies 512 steps of current (0 mA to
0.499 mA for a 1 mA reference current) which are also summed
into the I
or I
lines depending on the bits selected. In the fig-
O
O
ure, the code selected is: 100 110000000. Therefore, 2 mA (4
0.5 mA/segment) +0.375 mA (from master/slave D/A converter)
are summed into I
giving an I
of 2.375 mA. I
has a current
O
O
O
of 1.625 mA with this code. As the three MSB’s are increment-
ed, each successively higher code adds 0.5 mA to I
and sub-
Expanded Transfer Characteristic Segment (001 010 011)
O
tracts 0.5 mA from I
, with the selected resistor feeding its
O
current to the master/slave D/A converter; thus each increment
of the 3 MSBs allows the current in the 9-bit D/A converter to
be added to a pedestal consisting of the sum of all lower order
currents from the segment generator. This configuration guar-
antees monotonicity.
Simplified Schematic
REV. C
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