Datasheet

www.ti.com
THEORY OF OPERATION
DIGITAL-TO-ANALOG CONVERTER
DAC
Register
REF(+)
ResistorString
REF( )-
V H
REF
V
OUT
50kW
100kW 100kW
V
FB
V L
REF
RESISTOR STRING
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
SLAS441E – MARCH 2005 – REVISED APRIL 2007
The architecture of the DAC7551 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 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.
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.
11
Submit Documentation Feedback