DAC7802K Burr-Brown Corporation, DAC7802K Datasheet - Page 8

• Manufacturer Part Number: DAC7802K
• Description: Dual Monolithic CMOS 12-Bit Multiplying DIGITAL-TO-ANALOG CONVERTERS
• Manufacturer: Burr-Brown Corporation

DISCUSSION OF
SPECIFICATIONS
RELATIVE ACCURACY
This term, also known as end point linearity or integral
linearity, describes the transfer function of analog output to
digital input code. Relative accuracy describes the deviation
from a straight line, after zero and full scale errors have been
adjusted to zero.
DIFFERENTIAL NONLINEARITY
Differential nonlinearity is the deviation from an ideal 1LSB
change in the output when the input code changes by 1LSB.
A differential nonlinearity specification of 1LSB maximum
guarantees monotonicity.
GAIN ERROR
Gain error is the difference between the full-scale DAC
output and the ideal value. The ideal full scale output value
for the DAC780X is –(4095/4096)V
adjusted to zero using external trims as shown in Figures 5
and 7.
OUTPUT LEAKAGE CURRENT
The current which appears at I
loaded with all zeros.
OUTPUT CAPACITANCE
The parasitic capacitance measured from I
AGND.
CHANNEL-TO-CHANNEL ISOLATION
The AC output error due to capacitive coupling from DAC A
to DAC B or DAC B to DAC A.
MULTIPLYING FEEDTHROUGH ERROR
The AC output error due to capacitive coupling from V
I
OUTPUT CURRENT SETTLING TIME
The time required for the output current to settle to within
+0.01% of final value for a full scale step.
DIGITAL-TO-ANALOG GLITCH ENERGY
The integrated area of the glitch pulse measured in nanovolt-
seconds. The key contributor to digital-to-analog glitch is
charge injected by digital logic switching transients.
DIGITAL CROSSTALK
Glitch impulse measured at the output of one DAC but
caused by a full scale transition on the other DAC. The
integrated area of the glitch pulse is measured in nanovolt-
seconds.
CIRCUIT DESCRIPTION
Figure 1 shows a simplified schematic of one half of a
DAC780X. The current from the V
between I
CMOS switches. This maintains a constant current in each leg
OUT
with the DAC loaded with all zeros.
OUT A
®
and AGND by 12 single-pole double-throw
DAC7800, 01, 02
OUT A
and I
REF
REF A
. Gain error may be
OUT B
OUT A
pin is switched
with the DAC
or I
OUT B
REF
to
to
8
of the ladder regardless of the input code. The input resistance
at V
voltage or current, AC or DC, positive or negative polarity,
and have a voltage range up to 20V.
FIGURE 1. Simplified Circuit Diagram for DAC A.
A CMOS switch transistor, included in series with the ladder
terminating resistor and in series with the feedback resistor,
R
resistance of the ladder switches.
Figure 2 shows an equivalent circuit for DAC A. C
output capacitance due to the N-channel switches and varies
from about 30pF to 70pF with digital input code. The current
source I
ages to the substrate. I
R
with input code.
FIGURE 2. Equivalent Circuit for DAC A.
INSTALLATION
ESD PROTECTION
All digital inputs of the DAC780X incorporate on-chip ESD
protection circuitry. This protection is designed to withstand
2.5kV (using the Human Body Model, 100pF and 1500 ).
However, industry standard ESD protection methods should
be used when handling or storing these components. When
not in use, devices should be stored in conductive foam or
rails. The foam or rails should be discharged to the destina-
tion socket potential before devices are removed.
POWER SUPPLY CONNECTIONS
The DAC780X are designed to operate on V
For optimum performance and noise rejection, power supply
decoupling capacitors C
application circuits. These capacitors (1 F tantalum recom-
mended) should be located close to the D/A. AGND and
V
FB A
O
REF A
V
is the equivalent output resistance of the D/A and it varies
(MSB)
REF A
DB11
REF
, compensates for the temperature drift of the ON
LKG
R
2R
is therefore constant and can be driven by either a
R
is the combination of surface and junction leak-
DB10
4096
D
2R
IN
R
x
LKG
V
DB9
REF
R
D
approximately doubles every 10 C.
2R
should be added as shown in the
R
R
O
(LSB)
DB0
I
2R
LKG
DD
2R
R
C
= +5V +10%.
OUT
R
OUT
R
I
AGND A
OUT A
FB A
AGND
I
R
OUT A
FB A
is the