AD767KP Analog Devices Inc, AD767KP Datasheet - Page 5

• Manufacturer Part Number: AD767KP
• Description: IC DAC 12BIT W/AMP 28-PLCC
• Manufacturer: Analog Devices Inc

Specifications of AD767KP

• Data Interface: Parallel
• Rohs Status: RoHS non-compliant
• Settling Time: 3µs
• Number Of Bits: 12
• Number Of Converters: 1
• Voltage Supply Source: Dual ±
• Operating Temperature: 0°C ~ 70°C
• Mounting Type: Surface Mount
• Package / Case: 28-LCC (J-Lead)
• Resolution (bits): 12bit
• Sampling Rate: 500kSPS
• Input Channel Type: Parallel
• Supply Current: 18mA
• Digital Ic Case Style: LCC
• No. Of Pins: 25
• Power Dissipation (max): -
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

REV. A
BIPOLAR CONFIGURATION (Figure 3)
This configuration will provide a bipolar output voltage from
–5.000 to +4.9976 volts, with positive full scale occurring with
all bits ON (all 1s).
STEP I … OFFSET ADJUST
Turn OFF all bits. Adjust 100
volts output.
STEP II … GAIN ADJUST
Turn ON all bits. Adjust 100
reading of +4.9976 volts.
STEP III … BIPOLAR ZERO ADJUST (Optional)
In applications where an accurate zero output is required, set
the MSB ON, all other bits OFF, and readjust R1 for zero volts
output.
INTERNAL/EXTERNAL REFERENCE USE
The AD767 has an internal low-noise buried Zener diode
reference which is trimmed for absolute accuracy and tempera-
ture coefficient. This reference is buffered and optimized for use
in a high-speed DAC and will give long-term stability equal or
superior to the best discrete Zener reference diodes. The per-
formance of the AD767 is specified with the internal reference
driving the DAC since all trimming and testing (especially for
full-scale error and bipolar offset) is done in this configuration.
The internal reference has sufficient buffering to drive external
circuitry in addition to the reference currents required for the
DAC (typically 0.5 mA to Ref In and 1.0 mA to Bipolar Offset).
A minimum of 0.1 mA is available for driving external loads.
Figure 3.
5 V Bipolar Voltage Output
Figure 4. Using the AD767 with the AD588 High Precision Reference
gain trimmer R2 to give a
trimmer R1 to give –5.000
–5–
The AD767 reference output should be buffered with an
external op amp if it is required to supply more than 0.1 mA
output current. The reference is typically trimmed to 0.2%,
then tested and guaranteed to 1.0% max error. The
temperature coefficient is comparable to that of the full-scale
TC for a particular grade.
If an external reference is used (10.000 V, for example),
additional trim range must be provided, since the internal
reference has a tolerance of 1%, and the AD767 full-scale and
bipolar offset are both trimmed with the internal reference. The
gain and offset trim resistors give about 0.25% adjustment
range, which is sufficient for the AD767 when used with the
internal reference.
It is also possible to use external references other than 10 volts.
The recommended range of reference voltage is from +8 to
+10.5 volts, which allows both 8.192 V and 10.24 V ranges to
be used. The AD767 is optimized for fixed-reference applications.
If the reference voltage is expected to vary over a wide range in
a particular application, a CMOS multiplying DAC is a better
choice.
Reduced values of reference voltage will also permit the 12 volt
It is not recommended that the AD767 be used with external
feedback resistors to modify the scale factor. The internal
resistors are trimmed to ratio-match and temperature-track the
other resistors on the chip, even though their absolute tolerances
are 20%, and absolute temperature coefficients are approximately
–50 ppm/ C. If external resistors are used, a wide trim range
( 20%) will be needed and temperature drift will be increased
to reflect the mismatch between the temperature coefficients of
the internal and external resistors.
Small resistors may be added to the feedback resistors in order
to accomplish small modifications in the scaling. For example, if
a 10.24 V full scale is desired, a 140
resistor can be added in series with the internal (nominal) 5k
feedback resistor, and the gain trim potentiometer (between
Pins 6 and 7) should be increased to 200 . In the bipolar
mode, increase the value of the bipolar offset trim potentiometer
also to 200 .
5% power supply requirement to be relaxed to 12 volts
10%.
1% low-TC metal-film
AD767