參數(shù)資料
型號(hào): SDM872S
英文描述: 16 Single Ended/8 Differential Input 12-BIT DATA ACQUISITION SYSTEMS
中文描述: 16單端/ 8差分輸入12位數(shù)據(jù)采集系統(tǒng)
文件頁(yè)數(shù): 19/27頁(yè)
文件大?。?/td> 256K
代理商: SDM872S
SDM862/863/872/873
19
The STATUS output indicates the state of the converter by
being high only during a conversion. During this time the
three-state output buffers remain in a high-impedance state,
and therefore, data is not valid. During this period additional
transitions of the three control inputs will be ignored, so that
conversion cannot be prematurely terminated or restarted.
However, if BYTE SELECT changes state after the begin-
ning of conversion, any additional start conversion transition
will latch the new state of BYTE SELECT, possibly result-
ing in an incorrect conversion length (8 bit versus 12 bits)
for that conversion.
READING OUTPUT DATA
After conversion is initiated, the output data buffers remain
in a high-impedance state until the following four conditions
are met: R/C high, STATUS low, CE high, and CS low. In
this condition the data lines are enabled according to the
state of the inputs DATA MODE and BYTE SELECT. See
Read Cycle Timing for timing relationships and specifica-
tion.
In most applications the DATA MODE input will be
hardwired in either the high or low condition, although it is
fully TTL- and CMOS-compatible and may be actively
driven if desired. When DATA MODE is high, all 12
outputs lines (DB0-DB11 ) are enabled simultaneously for
full data word transfer to a 12-bit or 16-bit bus and the state
of the BYTE SELECT is ignored.
When DATA MODE is low, the data is presented in the
form of two 8-bit bytes, with selection of each byte by the
state of BYTE SELECT during the read cycle.
The BYTE SELECT input is usually driven by the least
significant bit of the address bus, allowing storage of the
output data word in two consecutive memory locations.
When BYTE SELECT is low, the byte addressed contains
the 8MSBs. When BYTE SELECT is high, the byte ad-
dressed contains the 4LSBs from the conversion followed by
four zeros that have been forced by the control logic. The
left-justified formats of the two 8-bit bytes are shown in
Figure 23. The design of the SDM guarantees that the BYTE
SELECT input may be toggled at any time without damage
to the output buffers occurring.
In the majority of applications, the read operation will be
attempted only after the conversion is complete and the
status output has gone low. In those situations requiring the
fastest possible access to the data, the read may be started as
much as (t
DD
max + t
HS
max) before STATUS goes low.
Refer to Read Cycle Timing for these timing relationships.
APPLICATIONS INFORMATION
ASSEMBLY OF SURFACE MOUNT PACKAGES
There are several assembly methods for the LCC versions of
the SDM8XX. The associated advantages and disadvantages
of three methods are outlined below.
1. DIRECT SURFACE MOUNT ONTO PCB
ADVANTAGES
DISADVANTAGES
Ease of assembly
Low cost
Low weight
Small footprint size
Difficult to inspect solder joints
Difficult to clean
Choice of board material important in
wide temperature range applications
In wide temperature applications it is important to match the
coefficients of thermal expansion of the board and the
SDM8XXL. Below is a list of materials and their approxi-
mate coefficients of linear thermal expansion.
MATERIAL
(ppm/
°
C)
Alumina (96%) - SDM Package
Copper-clad-Invar (50% Cu)
6-7
9
6
3
6
6
5
12
14
(30% Cu)
(10% Cu)
Epoxy-Kevlar (60% Kevlar)
Polyimide-Kevlar (40% Kevlar)
Beryllia
Polyimide-glass (x-axis)
(y-axis)
Kevlar E.I. du Pont de Nemours & Co.
2. ATTACHMENT OF
SURFACE MOUNT EDGE CLIPS
ADVANTAGES
DISADVANTAGES
Ease of Inspection
Easy cleaning
Thermal expansion taken up by
the flexing of the edge clips
Extra cost
Extra assembly
ASSEMBLY
The edge clips are attached to the edges of the SDM8XXL
as in Figure 24 before the device is mounted on to the board.
FIGURE 24. Edge Clip Assembly.
SDM
EDGE
CLIP
SUPPLIERS OF EDGE CLIPS
USA
USA
DIE-TECH INC.,
R.D. 1, Sipe Road,
York Haven,
PA 17370 USA
PHONE: (717) 938-6771
NAS Electronics,
381 Park St.,
Hackensack,
NJ 07602 USA
PHONE: (201) 343-3156
EUROPE
EUROPE
SEMI-DICE (UK) Ltd,
Buckingham House,
Mineral Lane,
Chesham,
Bucks. HP5 2AU UK
PHONE: 0494 771275
NASBRIT Ltd,
Wester Goudi Ind. Est.
Dundee DD2 4UX
UK
PHONE: 0382 622222
相關(guān)PDF資料
PDF描述
SDM873 16 Single Ended/8 Differential Input 12-BIT DATA ACQUISITION SYSTEMS
SDM873A 16 Single Ended/8 Differential Input 12-BIT DATA ACQUISITION SYSTEMS
SDM873B 16 Single Ended/8 Differential Input 12-BIT DATA ACQUISITION SYSTEMS
SDM873J 16 Single Ended/8 Differential Input 12-BIT DATA ACQUISITION SYSTEMS
SDM873K 16 Single Ended/8 Differential Input 12-BIT DATA ACQUISITION SYSTEMS
相關(guān)代理商/技術(shù)參數(shù)
參數(shù)描述
SDM873 制造商:BB 制造商全稱:BB 功能描述:16 Single Ended/8 Differential Input 12-BIT DATA ACQUISITION SYSTEMS
SDM873A 制造商:BB 制造商全稱:BB 功能描述:16 Single Ended/8 Differential Input 12-BIT DATA ACQUISITION SYSTEMS
SDM873B 制造商:BB 制造商全稱:BB 功能描述:16 Single Ended/8 Differential Input 12-BIT DATA ACQUISITION SYSTEMS
SDM873J 制造商:BB 制造商全稱:BB 功能描述:16 Single Ended/8 Differential Input 12-BIT DATA ACQUISITION SYSTEMS
SDM873K 制造商:BB 制造商全稱:BB 功能描述:16 Single Ended/8 Differential Input 12-BIT DATA ACQUISITION SYSTEMS