DAC7800_04 BURR-BROWN [Burr-Brown Corporation], DAC7800_04 Datasheet - Page 8

• Manufacturer Part Number: DAC7800_04
• Description: Dual Monolithic CMOS 12-Bit Multiplying DIGITAL-TO-ANALOG CONVERTERS
• Manufacturer: BURR-BROWN [Burr-Brown Corporation]

8
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
ensures 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
to zero using external trims, see 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 DAC 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
AGND by 12 single-pole double-throw CMOS switches. This
maintains a constant current in each leg of the ladder regard-
less of the input code. The input resistance at V
OUT
with the DAC loaded with all zeros.
REF A
pin is switched between I
REF
OUT A
. Gain error may be adjusted
and I
OUT B
OUT A
REF
with the DAC
is therefore
or I
OUT A
OUT B
REF
and
www.ti.com
to
to
constant and can be driven by either a 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
tance 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 DAC. AGND and
V
FB A
O
REF A
V
is the equivalent output resistance of the DAC and it varies
(MSB)
REF A
DB11
, compensates for the temperature drift of the ON resis-
R
LKG
2R
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.
should be added as shown in the
2R
R
DAC7800, 7801, 7802
R
O
(LSB)
DB0
I
2R
LKG
SBAS005A
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