DAC7641Y Burr-Brown Corporation, DAC7641Y Datasheet - Page 13

• Manufacturer Part Number: DAC7641Y
• Description: 16-Bit/ Voltage Output DIGITAL-TO-ANALOG CONVERTER
• Manufacturer: Burr-Brown Corporation

ANALOG OUTPUTS
When V
fier can swing to within 2.25V of the supply rails, guaran-
teed over the –40 C to +85 C temperature range. With V
= 0V (single-supply operation), and with R
nected to ground, the output can swing to ground. Care must
be taken when measuring the zero-scale error with V
Since the output voltage cannot swing below ground, the
output voltage may not change for the first few digital input
codes (0000
a negative offset. At the negative limit of –2mV, the first
specified output starts at code 0040
Due to the high accuracy of these D/A converters, system
design problems such as grounding and contact resistance
become very important. A 16-bit converter with a 2.5V full-
scale range has a 1LSB value of 38 V. With a load current
of 1mA, series wiring and connector resistance (see Figure
4) of only 40m
To understand what this means in terms of a system layout,
the resistivity of a typical 1 ounce copper-clad printed circuit
board is 1/2 m per square. For a 1mA load, a 10 milli-inch
wide printed circuit conductor 600 milli-inches long will
result in a voltage drop of 30 V.
The DAC7641 offers a force and sense output configuration
for the high open-loop gain output amplifier. This feature
allows the loop around the output amplifier to be closed at the
load (see Figure 4), thus ensuring an accurate output voltage.
REFERENCE INPUTS
The reference inputs, V
between V
at least 1.25V greater than V
each DAC is equal to V
(essentially, the offset of the output op amp). The maximum
output is equal to V
that V
FIGURE 5. Dual Supply Configuration-Buffered References, used for Dual Supply Performance Curves.
SS
SS
SS
(the negative power supply) must either be
= –5V (dual supply operation), the output ampli-
H
+ 2.5V and V
, 0001
(R
500pF
H
REF
W2
, 0002
) will cause a voltage drop of 40 V.
H plus a similar offset voltage. Note
REF
REF
CC
H
L and V
, etc.) if the output amplifier has
REF
– 2.5V provided that V
L plus a small offset voltage
L. The minimum output of
REF
H
.
H, can be any voltage
DAC7641
LOAD
V
OUT
Sense
V
also con-
OUT
SS
REF
= 0V.
24
23
22
H is
SS
500pF
V
SS
13
connected to ground or must be in the range of –4.75V to
–5.25V. The voltage on V
the converter. If V
tions, the bias values may be in error and proper operation
of the device is not guaranteed.
The current into the V
on the DAC output voltages and can vary from a few
microamps to approximately 0.5mA. The reference input
appears as a varying load to the reference. If the reference
can sink or source the required current, a reference buffer is
not required. The DAC7641 features a reference drive and
sense connection such that the internal errors caused by the
changing reference current and the circuit impedances can
be minimized. Figures 5 through 13 show different reference
configurations and the effect on the linearity and differential
linearity.
FIGURE 4. Analog Output Closed-Loop Configuration. R
V
OUT
OPA2234
represents wiring resistances.
DAC7641
SS
is not in one of these two configura-
REF
V
OUT
H input and out of V
SS
Sense
V
OUT
sets several bias points within
DAC7641
–V
+V
24
23
22
+V
–2.5V
+2.5V
V
SS
+2.5V
R
R
W1
W2
REF
L depends
V
OUT
W
®