DAC712
www.ti.com ................................................................................................................................................. SBAS023A–SEPTEMBER 2000–REVISED JULY 2009
LOGIC INPUT COMPATIBILITY
GAIN AND OFFSET ADJUSTMENTS
The DAC712 digital inputs are TTL-compatible (1.4V
switching level) with low-leakage, high-impedance
inputs. Thus, the inputs are suitable for being driven
by any type of 5V logic such as 5V CMOS logic. An
equivalent circuit of a digital input is shown in
Figure 9.
Figure 10 illustrates the relationship of offset and gain
adjustments for a bipolar connected D/A converter.
Offset should be adjusted first to avoid interaction of
adjustments. Table 1 shows calibration values and
codes. These adjustments have a minimum range of
±0.3%.
Data inputs float to logic '0' and control inputs float to
logic '0' if left unconnected. It is recommended that
any unused inputs be connected to DCOM to improve
noise immunity.
Range of
+ Full-Scale
Gain Adjust
» ±0.3%
1LSB
Digital inputs remain high-impedance when power is
off.
Full-Scale
All Bits
Range
Gain Adjust
Rotates the Line
Logic 0
+VCC
ESD Protection Circuit
Bipolar
Offset
All Bits
Logic 1
R = 1k: A0, A1, WR, CLR
3k: D0...D15
MSB on All
Others Off
R
Range of
Offset Adjust
Digital
Input
- Full-Scale
Offset Adjust
Translates
the Line
6.8V
5pF
Digital Input
-VCC
» ±0.3%
Figure 10. Relationship of Offset and Gain
Adjustments
Figure 9. Equivalent Circuit of Digital Inputs
INPUT CODING
Table 1. Digital Input and Analog Output Voltage
Calibration Values
The DAC712 is designed to accept positive-true
binary twos complement (BTC) input codes that are
compatible with bipolar analog output operation. For
bipolar analog output configuration, a digital input of
7FFFh gives a positive full-scale output, 8000h gives
a negative full-scale output, and 0000h gives bipolar
zero output.
DAC712 CALIBRATION VALUES
1 LEAST SIGNIFICANT BIT = 305µV
DIGITAL INPUT
CODE BINARY
TWOS
COMPLEMENT,
BTC
ANALOG OUTPUT
(V)
DESCRIPTION
Positive Full-Scale –
1LSB
7FFFh
+9.999695
INTERNAL REFERENCE
4000h
0001h
0000h
FFFFh
C000h
8000h
+5.000000
+0.000305
0.000000
3/4 Scale
BPZ + 1LSB
The DAC712 contains a +10V reference.
The reference output may be used to drive external
loads, sourcing up to 2mA. The load current should
be constant, otherwise the gain and bipolar offset of
the converter will vary.
Bipolar Zero (BPZ)
BPZ – 1LSB
–0.000305
–5.000000
–10.00000
1/4 Scale
Negative Full-Scale
OUTPUT VOLTAGE SWING
The output amplifier of the DAC712 is committed to a
±10V output range. The DAC712 provides a ±10V
output swing while operating on ±11.4V or higher
voltage supplies.
Offset Adjustment
Apply the digital input code that produces the
maximum negative output voltage and adjust the
offset potentiometer or the offset adjust D/A converter
for –10V.
Copyright © 2000–2009, Texas Instruments Incorporated
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