SNAS534B – MAY 1999 – REVISED MARCH 2013
is high.
WR
2
: Write 2
(active low). This signal, in combination with XFER, causes the 8-bit data which is available in the
input latch to transfer to the DAC register.
XFER: Transfer control signal
(active low). The XFER will enable WR
2
.
Other Pin Functions
DI
0
-DI
7
: Digital Inputs.
DI
0
is the least significant bit (LSB) and DI
7
is the most significant bit (MSB).
I
OUT1
: DAC Current Output 1.
I
OUT1
is a maximum for a digital code of all 1's in the DAC register, and is zero for
all 0's in DAC register.
I
OUT2
: DAC Current Output 2.
I
OUT2
is a constant minus I
OUT1
, or I
OUT1
+ I
OUT2
= constant (I full scale for a fixed
reference voltage).
R
fb
:
Feedback Resistor.
The feedback resistor is provided on the IC chip for use as the shunt feedback
resistor for the external op amp which is used to provide an output voltage for the DAC. This on-chip
resistor should always be used (not an external resistor) since it matches the resistors which are used in
the on-chip R-2R ladder and tracks these resistors over temperature.
V
REF
: Reference Voltage Input.
This input connects an external precision voltage source to the internal R-2R
ladder. V
REF
can be selected over the range of +10 to
−10V.
This is also the analog voltage input for a 4-
quadrant multiplying DAC application.
V
CC
: Digital Supply Voltage.
This is the power supply pin for the part. V
CC
can be from +5 to +15V
DC
.
Operation is optimum for +15V
DC
GND:
The pin 10 voltage must be at the same ground potential as I
OUT1
and I
OUT2
for current switching
applications. Any difference of potential (V
OS
pin 10) will result in a linearity change of :
(1)
For example, if V
REF
= 10V and pin 10 is 9mV offset from I
OUT1
and I
OUT2
the linearity change will be 0.03%.
Pin 3 can be offset ±100mV with no linearity change, but the logic input threshold will shift.
Linearity Error
Figure 3. a) End Point Test After
Zero and fs adj.
Figure 4. b) Best Straight Line
Figure 5. c) Shifting fs adj. to
Pass
Best Straight Line Test
Definition of Terms
Resolution:
Resolution is directly related to the number of switches or bits within the DAC. For example, the
DAC0830 has 2
8
or 256 steps and therefore has 8-bit resolution.
Linearity Error:
Linearity Error is the maximum deviation from a
straight line passing through the endpoints of
the DAC transfer characteristic.
It is measured after adjusting for zero and full-scale. Linearity error is a
parameter intrinsic to the device and cannot be externally adjusted.
6
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