DataSheet8.cn


PDF ( 数据手册 , 数据表 ) DAC16FP

零件编号 DAC16FP
描述 16-Bit High Speed Current-Output DAC
制造商 Analog Devices
LOGO Analog Devices LOGO 


1 Page

No Preview Available !

DAC16FP 数据手册, 描述, 功能
a
FEATURES
؎1 LSB Differential Linearity (max)
Guaranteed Monotonic Over Temperature Range
؎2 LSB Integral Linearity (max)
500 ns Settling Time
5 mA Full-Scale Output
TTL/CMOS Compatible
Low Power: 190 mW (typ)
Available in Die Form
APPLICATIONS
Communications
ATE
Data Acquisition Systems
High Resolution Displays
16-Bit High Speed
Current-Output DAC
DAC16
FUNCTIONAL BLOCK DIAGRAM
IREF
REF GND
VCC
AGND
VEE
DGND
BUFFER
DAC16
CCOMP
DAC
IOUT
DB0 (LSB)
DB15 (MSB)
GENERAL DESCRIPTION
The DAC16 is a 16-bit high speed current-output digital-to-
analog converter with a settling time of 500 ns. A unique com-
bination of low distortion, high signal-to-noise ratio, and high
speed make the DAC16 ideally suited to performing waveform
synthesis and modulation in communications, instrumentation,
and ATE systems. Input reference current is buffered, with full-
scale output current of 5 mA. The 16-bit parallel digital input
bus is TTL/CMOS compatible. Operating from +5 V and
–15 V supplies, the DAC16 consumes 190 mW (typ) and is
available in a 24-lead epoxy DIP, epoxy surface-mount small
outline (SOL), and in die form.
0.1
0.01
VLOGIC = +5V
TURNING OFF
VLOGIC = 0V
TURNING ON
IFS = 4mA
TA = 25؇C
0.001
0
100 200 300 400 500 600 700 800
SETTLING TIME – ns
Figure 1. DAC16 Settling Time Accuracy vs. Percent of
Full Scale
REV. B
Information furnished by Analog Devices is believed to be accurate and
reliable. However, no responsibility is assumed by Analog Devices for its
use, nor for any infringements of patents or other rights of third parties
which may result from its use. No license is granted by implication or
otherwise under any patent or patent rights of Analog Devices.
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 781/329-4700 World Wide Web Site: http://www.analog.com
Fax: 781/326-8703
© Analog Devices, Inc., 1999







DAC16FP pdf, 数据表
DAC16
reference amplifier. Completely removing the compensation
network would introduce large linearity errors, reference amplifier
instability, wideband reference amplifier noise, and poor settling
time.
Because the DAC exhibits an internal current scaling factor of
eight times (8×), the reference amplifier requires only 500 µA
input current from the user-supplied precision reference for a
4 mA full-scale output current. In applications that do not re-
quire such high output currents, good accuracy can be achieved
with input reference currents in the range of 350 µA IREF
625 µA. The best signal-to-noise ratios, of course, will be
achieved with a 625 µA reference current which yields a maxi-
mum 5 mA output current. Figure 22 illustrates how to form
the reference input current with a REF02 and a 10 kprecision
resistor.
+15V
0.1F
REF02
RREF
10k
IREF DAC16
REF GND
IOUT
IREF
=
VREF
RREF
Figure 22. Generating the DAC16’s Reference Input Current
Reducing Voltage Reference Noise
In data converters of 16-bit and greater resolution, noise is of
critical importance. Surprisingly, the integrated voltage refer-
ence circuit used may contribute the dominant share of a
system’s noise floor, thereby degrading system dynamic range
and signal-to-noise ratio. To maximize system dynamic range
and SNR, all external noise contributions should be effectively
much less than 1/2 LSB. For example, in a 5 V DAC16 applica-
tion, one LSB is equivalent to 76 µV. This means that the total
wideband noise contribution due to a voltage reference and all
other sources should be less than 38 µV rms. These noise levels
are not easy targets to hit with standard off-the-shelf reference
devices. For example, commercially available references might
exhibit 5 µV rms noise from 0.1 Hz to 10 Hz: but, over a 100 kHz
bandwidth, its 300 µV rms of noise can easily swamp out a
16-bit system. Such noisy behavior can degrade a DAC’s effec-
tive resolution by increasing its differential nonlinearity which,
in turn, can lead to nonmonotonic behavior or analog errors.
The easiest way to reduce noise in the reference circuit is to
band-limit its noise before feeding it to the converter. In the
case of the DAC16, the reference is not a voltage, but a current.
Illustrated in Figure 23 is a simple way of hand-limiting
+15V
0.1F
REF02
R1 R2
5k5k
IREF DAC16
C1
22F
REF GND
AGND
Figure 23. Filtering a Reference’s Wideband Noise
voltage reference noise by splitting RREF into two equal resistors
and bypassing the common node with a capacitor. To minimize
thermally induced errors, R1 and R2 must be electrically and
thermally well-matched. Thin-film resistor networks work well
here. In this circuit, the parallel combination of R1 and R2
forms a 3 Hz low-pass filter with C1. The only noise source that
remains is the thermal noise of R2 which can be a significantly
lower noise generator than the voltage reference.
Input Coding
The unipolar digital input coding of the DAC16 employs nega-
tive logic to control the output current; that is, an all zero input
code (0000H) yields an output current 1 LSB below full scale.
Conversely, an all 1s input code (FFFFH) yields a zero analog
current output. An expression for the DAC16’s transfer equa-
tion can be expressed by:
IOUT
= 8 × IREF
×
65,
535
Digital
 65,536
Code

Table II provides the relationship between the digital input
codes and the output current of the DAC16.
Table II. Unipolar Code Table
Digital Input
Word (Hex)
0000
7FFE
7FFF
8000
FFFF
DAC16 Output
Current IOUT
8 × (216 – 1)/216 × IREF
8 × (215 + 1)/216 × IREF
8 × (215/216) × IREF
8 × (215– 1)/216 × IREF
0
Comment
Full Scale
Midscale + 1 LSB
Midscale
Midscale – 1 LSB
Zero Scale
Since the DAC16 exhibits a small output voltage compliance on
the order of a few millivolts, a high accuracy operational ampli-
fier must be used to convert the DAC’s output current to a volt-
age. Refer to the section on selecting operation amplifiers for the
DAC16. The circuit shown in Figure 24 illustrates a unipolar
output configuration. In symbolic form, the transfer equation
for this circuit can be expressed by:
VO
=
R3
×
8
×
IREF
65,535 – Digital
 65,536
Code

In this example, the reference input current was set to 500 µA
which produces a full-scale output current of 4 mA – 1 LSB.
The DAC’s output current was scaled by R3, a 1.25 kresistor,
to produce a 5 V full-scale output voltage. Bear in mind that to
ensure the highest possible accuracy, matched thin-film resistor
networks are almost a necessity, not an option. The resistors
used in the circuit must have close tolerance and tight thermal
tracking. Table III illustrates the relationship between the input
digital code and the circuit’s output voltage for the component
values shown.
Table III. Unipolar Output Voltage vs. Digital Input Code
Digital Input Word Decimal Number in Analog Output
(Hex)
in DAC Decoder
Voltage (V)
0000
7FFE
7FFF
8000
FFFF
65,535
32,769
32,768
32,767
0
4.999924
2.500076
2.500000
2.499924
0
–8– REV. B














页数 12 页
下载[ DAC16FP.PDF 数据手册 ]


分享链接

Link :

推荐数据表

零件编号描述制造商
DAC16FP16-Bit High Speed Current-Output DACAnalog Devices
Analog Devices
DAC16FS16-Bit High Speed Current-Output DACAnalog Devices
Analog Devices

零件编号描述制造商
STK15C88256-Kbit (32 K x 8) PowerStore nvSRAMCypress Semiconductor
Cypress Semiconductor
NJM4556DUAL HIGH CURRENT OPERATIONAL AMPLIFIERNew Japan Radio
New Japan Radio
EL1118-G5 PIN LONG CREEPAGE SOP PHOTOTRANSISTOR PHOTOCOUPLEREverlight
Everlight


DataSheet8.cn    |   2020   |  联系我们   |   搜索  |  Simemap