DAC8426FP Analog Devices Inc, DAC8426FP Datasheet - Page 9

• Manufacturer Part Number: DAC8426FP
• Description: IC DAC 8BIT QUAD 10VREF 20-DIP
• Manufacturer: Analog Devices Inc

Specifications of DAC8426FP

• Rohs Status: RoHS non-compliant
• Settling Time: 3µs
• Number Of Bits: 8
• Number Of Converters: 4
• Voltage Supply Source: Dual ±
• Power Dissipation (max): 210mW
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Through Hole
• Package / Case: 20-DIP (0.300", 7.62mm)
• Data Interface: -

APPLICATIONS SETUP
UNIPOLAR OUTPUT OPERATION
The output voltage appearing at any output V
internal 10 V reference multiplied by the decimal value of the
latched digital input divided by 2
where D = 0
Note that the maximum possible output is 1 LSB less than the
internal 10 V reference, that is, 255/256 10 V = 9.961 V.
Table II lists output voltages for a given digital input. The total
unadjusted error (TUE) specification of the product grade used
determines the output tolerances of the values listed in Table II.
For example, a 2 LSB grade DAC8426FP loaded with decimal
128
curring in the range of 5 V 2 LSB, which is 5 V (2 10 V/256)
= 5 V 0.078 V. Therefore V
following range:
(TUE), the guaranteed range is 4.961 V V
These tolerances provide the worst case analysis including tem-
perature changes.
REV. C
For the top grade DAC8426EP 1 LSB total unadjusted error
10
(half-scale) would have a guaranteed output voltage oc-
10
Figure 5. DAC Output Current Sink
Figure 4. Amplifier Output Stage
to 255
4.922 V
V
OUT
10
(D) = D/256
V
OUT
OUT
(128)
8
is guaranteed to occur in the
(= 256). In equation form:
10 V
5.078 V
OUT
OUT
(128
is equal to the
10
) 5.039 V.
–9–
One additional characteristic guaranteed is a DNL of 1 LSB
on all grades. The DAC8426 is therefore guaranteed to be mon-
otonic. In the situation where a continuously positive 1 LSB
digital increment is applied, the output voltage will always in-
crease in value, never decrease. This is very important is servo
applications and other closed-loop feedback systems. Finally, in
the typical characteristic curves, long term output voltage drift
(stability) is provided.
BIPOLAR OUTPUT OPERATION
An external op amp plus two resistors can easily convert any
DAC output to bipolar output voltage swings. Figure 6 shows all
four DACs output operating in bipolar mode. This is the general
expression describing the bipolar output transfer equation:
where D = 0
If R
Table III lists various output voltages with R
input code. This coding is considered offset binary. Note that
the LSB step size is now 20 V/256 = 0.078 V, twice as large as
the unipolar output case previously discussed. In order to minimize
gain and offset errors, choose R
within 0.1% over the selected operating temperature range
of interest.
Digital Input
Code
255
254
129
128
127
1
0
OFFSETTING AGND
Since the DAC ladder and bandgap reference are terminated at
AGND, it is possible to offset AGND positive with respect to
DGND. The 10 V output span remains if a positive offset is ap-
plied to AGND. The offset voltage source connected to AGND
must be capable of sinking 14 mA. AGND cannot be taken
negative with respect to DGND; this would forward bias an in-
ternal diode. Allowance must be made at V
of headroom above V
in single supply applications where virtual ground needs to be
slightly positive with respect to ground. In this application con-
nect V
current sinking capability when the DAC output is programmed
to all zeros code, see Figure 7.
1
V
= R
OUT
Table II. Unipolar Output Voltage as a Function of
Digital Input Code
SS
to DGND to take advantage of the extra buffer output
2
(D) = [(1 +R
, then V
10
to 255
V
OUT
OUT
10
REF
becomes:
2
(D) = (D/128–1)
/R
OUT. This connection setup is useful
1
)
D/256
1
Analog Output
Voltage (= D/256 10 V)
9.961 V
9.922 V
5.039 V
5.000 V
4.961 V
0.039 V
0.000 V
and R
10 V] –R
2
to match and track
10 V
DD
1
DAC8426
= R
to maintain 3.5 V
Full-Scale (FS)
FS-1 LSB
1 LSB
Half-Scale
Zero-Scale
2
/R
2
1
versus digital
10 V,