công cụ tìm kiếm bảng dữ liệu linh kiện điện tử
  Vietnamese  ▼
ALLDATASHEET.VN

X  

AD668SQ bảng dữ liệu(PDF) 7 Page - Analog Devices

tên linh kiện AD668SQ
Giải thích chi tiết về linh kiện  12-Bit Ultrahigh Speed Multiplying D/A Converter
Download  16 Pages
Scroll/Zoom Zoom In 100%  Zoom Out
nhà sản xuất  AD [Analog Devices]
Trang chủ  http://www.analog.com
Logo AD - Analog Devices

AD668SQ bảng dữ liệu(HTML) 7 Page - Analog Devices

Back Button AD668SQ Datasheet HTML 3Page - Analog Devices AD668SQ Datasheet HTML 4Page - Analog Devices AD668SQ Datasheet HTML 5Page - Analog Devices AD668SQ Datasheet HTML 6Page - Analog Devices AD668SQ Datasheet HTML 7Page - Analog Devices AD668SQ Datasheet HTML 8Page - Analog Devices AD668SQ Datasheet HTML 9Page - Analog Devices AD668SQ Datasheet HTML 10Page - Analog Devices AD668SQ Datasheet HTML 11Page - Analog Devices Next Button
Zoom Inzoom in Zoom Outzoom out
 7 / 16 page
background image
AD668
REV. A
–7–
The variations in DAC settling and rise times can be attributed
to differences in rise time and current driving capabilities of the
various families. Differences in the glitch impulse are predomi-
nantly dependent upon the variation in data skew. Variations in
these specs occur not only between logic families, but also be-
tween different gates and latches within the same family. When
selecting a gate to drive the AD668 logic input, pay particular
attention to the propagation delay time specs: tPLH and tPHL.
Selecting the smallest delays possible will help to minimize the
settling time, while selection of gates where tPLH and tPHL are
closely matched to one another will minimize the glitch impulse
resulting from data skew. Of the common latches, the 74374
octal flip-flop provides the best performance in this area for
many of the logic families mentioned above.
PIN BY PIN CURRENT ACCOUNTING
The internal wiring and pinout of the AD668 are dictated in
large part by current management constraints. When using low
impedance, high current, high accuracy parts such as the
AD668, great care must be taken in the routing of not only sig-
nal lines, but ground and supply lines as well. The following ac-
counting provides a detailed description of the magnitudes and
signal dependencies of the currents associated with each of the
part’s pins. These descriptions are consistent with the functional
block diagram as well as the equivalent circuits provided in Fig-
ures 4, 5, and 6.
VCC – the current into this pin is drawn predominantly through
the DAC current sources and generally runs about 2.2 times the
DAC’s nominal full scale. By design, this current is independent
of the digital input code but is linearly dependent on analog in-
put variations.
REFCOM – this node provides the reference ground for the
reference amplifier’s current feedback loop (as illustrated in Fig-
ure 5) as well as providing the negative supply voltage for most
of the reference amplifier. The current consists of 1.2 mA of
analog input dependent current and another 3 mA of input in-
dependent current. Analog input voltages should always be pro-
duced with respect to this voltage.
REFIN1 – has a 1k series resistance to the reference amplifier
input and a 5k series resistance to REFIN2. REFIN1 may be
used in conjunction with REFIN2 to provide a 5:1 voltage di-
vider, or the two may be driven in parallel to provide a high
impedance input node (see Figure 5).
REFIN2 – the 4k side of the input resistive divider. Note also
that the combined impedance of these two resistors matches the
effective impedance at the other input of the reference amplifier,
thereby minimizing the offset due to bias currents. Circuits
which alter this effective impedance may suffer increased analog
offset and drift performance degradation as a result of the mis-
match in these impedances.
IOUT – the output current. In the current output mode with this
node tied to a virtual ground, a 10.24 mA nominal full scale
output current will flow from this pin. In the voltage output
mode, with RL grounded, half of the output current will flow
out of RL and the other half will flow out of LCOM. External
resistive loading will cause current to be divided between
LCOM, RL, and IOUT as Figure 4 suggests.
DIGITAL INPUT CONSIDERATIONS
The AD668 uses a standard positive true straight binary code
for unipolar outputs (all 1s full-scale output), and an offset bi-
nary code for bipolar output ranges. In the bipolar mode, with
all 0s on the inputs, the output will go to negative full scale;
with 111 . . . 11, the output will go to positive full scale less
1 LSB; and with 100 . . . 00 (only the MSB on), the output will
go to zero.
The threshold of the digital inputs is set at 1.4 V and does not
vary with supply voltage. This reference is provided by a band-
gap generator, which requires approximately 3 mA of bias
current achieved by tying RTH to any +VLOGIC supply where:
R
TH =
+V
LOGIC –1. 4 V
3 mA


(see Figure 6). The digital bit inputs operate with small input
currents to easily interface to unbuffered CMOS logic. The digi-
tal input signals to the DAC should be isolated from the analog
input and output as much as possible. To minimize undershoot,
ringing, and digital feedthrough noise, the interconnect distance
to the DAC inputs should be kept as short as possible. Termina-
tion resistors may improve performance if the digital lines be-
come too long. The digital inputs should be free from large
glitches and ringing and have 10% to 90% rise and fall times on
the order of 5 ns.
Figure 6. Equivalent Digital Input
To realize the AD668’s specified ac performance, it is recom-
mended that high speed logic families such as Schottky TTL,
high speed CMOS, or the new lines of high speed TTL be used
exclusively. Table I shows how DAC performance, particularly
glitch, can vary depending on the driving logic used. As this
table indicates, STTL, HCMOS, and FAST* represent the
most viable families for driving the AD668.
Table I. DAC Performance vs. Drive Logic
10%-90%
2
Settling Time
2, 3
Maximum
Logic
DAC Rise
1 LSB
Glitch
4
Glitch
Family
1
Time
1%
0.1% (0.025%)
Impulse Excursion
TTL
10.5 ns
47 ns
77 ns 100 ns
2.5 nV-s
280 mV
LSTTL
11.25 ns
35 ns
60 ns 120 ns
1.2 nV-s
270 mV
STTL
11 ns
50 ns
75 ns 110 ns
500 pV-s 200 mV
HCMOS 12 ns
53 ns
78 ns 100 ns
350 pV-s 200 mV
FAST*
11.5 ns
49 ns
73 ns 100 ns
2 nV-s
250 mV
NOTES
1All values typical, taken in test fixture diagrammed in Figure 23.
2Measurements are made for a 1 V full-scale step into 100
Ω DAC load resistance.
3Settling time is measured from the time the digital input crosses the threshold
voltage (1.4 V) to when the output is within the specified range of its final value.
4The worst case glitch impulse, measured on the major carry. DAC full scale is1 V.
*FAST is a registered trademark of National Semiconductor Corporation.


Số phần tương tự - AD668SQ

nhà sản xuấttên linh kiệnbảng dữ liệuGiải thích chi tiết về linh kiện
logo
Analog Devices
AD668SQ AD-AD668SQ Datasheet
602Kb / 16P
   12-Bit Ultrahigh Speed Multiplying D/A Converter
REV. A
More results

Mô tả tương tự - AD668SQ

nhà sản xuấttên linh kiệnbảng dữ liệuGiải thích chi tiết về linh kiện
logo
Analog Devices
AD668 AD-AD668 Datasheet
602Kb / 16P
   12-Bit Ultrahigh Speed Multiplying D/A Converter
REV. A
AD668 AD-AD668_15 Datasheet
250Kb / 16P
   12-Bit Ultrahigh Speed Multiplying D/A Converter
REV. A
DAC312 AD-DAC312_15 Datasheet
272Kb / 14P
   12-Bit High Speed Multiplying D/A Converter
DAC312HSZ AD-DAC312HSZ Datasheet
240Kb / 14P
   12-Bit High Speed Multiplying D/A Converter
REV. C
DAC312 AD-DAC312 Datasheet
269Kb / 14P
   12-Bit High Speed Multiplying D/A Converter
REV. C
AD568 AD-AD568_15 Datasheet
544Kb / 14P
   12-Bit Ultrahigh Speed Monolithic D/A Converter
REV. A
AD568 AD-AD568 Datasheet
541Kb / 14P
   12-Bit Ultrahigh Speed Monolithic D/A Converter
REV. A
AD568 AD-AD568_17 Datasheet
575Kb / 15P
   12-Bit Ultrahigh Speed Monolithic D/A Converter
logo
NXP Semiconductors
AM6012 PHILIPS-AM6012 Datasheet
107Kb / 11P
   12-Bit multiplying D/A converter
August 31, 1994
logo
Intersil Corporation
AD7541 INTERSIL-AD7541_02 Datasheet
164Kb / 8P
   12-Bit, Multiplying D/A Converter
More results


Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16


bảng dữ liệu tải về

Go To PDF Page


Link URL




Chính sách bảo mật
ALLDATASHEET.VN
Cho đến nay ALLDATASHEET có giúp ích cho doanh nghiệp của bạn hay không?  [ DONATE ] 

Alldatasheet là   |   Quảng cáo   |   Liên lạc với chúng tôi   |   Chính sách bảo mật   |   Trao đổi link   |   Tìm kiếm theo nhà sản xuất
All Rights Reserved©Alldatasheet.com


Mirror Sites
English : Alldatasheet.com  |   English : Alldatasheet.net  |   Chinese : Alldatasheetcn.com  |   German : Alldatasheetde.com  |   Japanese : Alldatasheet.jp
Russian : Alldatasheetru.com  |   Korean : Alldatasheet.co.kr  |   Spanish : Alldatasheet.es  |   French : Alldatasheet.fr  |   Italian : Alldatasheetit.com
Portuguese : Alldatasheetpt.com  |   Polish : Alldatasheet.pl  |   Vietnamese : Alldatasheet.vn
Indian : Alldatasheet.in  |   Mexican : Alldatasheet.com.mx  |   British : Alldatasheet.co.uk  |   New Zealand : Alldatasheet.co.nz
Family Site : ic2ic.com  |   icmetro.com