Datasheet

DAC
Register
REF(+)
ResistorString
REF( )-
V H
REF
V
OUT
50kW
100kW 100kW
V
FB
V L
REF
V
REF
H
V
REF
L
R
R
R
R
V
REF
H V L-
REF
2
R
DIVIDER
ToOutputAmplifier
(2xGain)
DAC7551-Q1
SLAS767 –JUNE 2011 www.ti.com
THEORY OF OPERATION
DIGITAL-TO-ANALOG CONVERTER
The architecture of the DAC7551-Q1 consists of a
string DAC followed by an output buffer amplifier.
Figure 26 shows a generalized block diagram of the
DAC architecture.
Figure 26. Typical DAC Architecture
The input coding to the DAC7551-Q1 is unsigned
binary, which gives the ideal output voltage as:
V
OUT
= 2 x V
REF
L + (V
REF
H – V
REF
L) x D/4096
Where D = decimal equivalent of the binary code that
is loaded to the DAC register, which ranges from 0 to
4095.
RESISTOR STRING
The resistor string section is shown in Figure 27. It is
simply a string of resistors, each of value R. The
digital code loaded to the DAC register determines at
which node on the string the voltage is tapped off to
Figure 27. Typical Resistor String
be fed into the output amplifier. The voltage is tapped
off by closing one of the switches connecting the
string to the amplifier. It is specified monotonic
because it is a string of resistors.
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