Technical Library | 2020-07-08 20:05:59.0
There is a compelling need for functional testing of high-speed input/output signals on circuit boards ranging from 1 gigabit per second (Gbps) to several hundred Gbps. While manufacturing tests such as Automatic Optical Inspection (AOI) and In-Circuit Test (ICT) are useful in identifying catastrophic defects, most high-speed signals require more scrutiny for failure modes that arise due to high-speed conditions, such as jitter. Functional ATE is seldom fast enough to measure high-speed signals and interpret results automatically. Additionally, to measure these adverse effects it is necessary to have the tester connections very close to the unit under test (UUT) as lead wires connecting the instruments can distort the signal. The solution we describe here involves the use of a field programmable gate array (FPGA) to implement the test instrument called a synthetic instrument (SI). SIs can be designed using VHDL or Verilog descriptions and "synthesized" into an FPGA. A variety of general-purpose instruments, such as signal generators, voltmeters, waveform analyzers can thus be synthesized, but the FPGA approach need not be limited to instruments with traditional instrument equivalents. Rather, more complex and peculiar test functions that pertain to high-speed I/O applications, such as bit error rate tests, SerDes tests, even USB 3.0 (running at 5 Gbps) protocol tests can be programmed and synthesized within an FPGA. By using specific-purpose test mechanisms for high-speed I/O the test engineer can reduce test development time. The synthetic instruments as well as the tests themselves can find applications in several UUTs. In some cases, the same test can be reused without any alteration. For example, a USB 3.0 bus is ubiquitous, and a test aimed at fault detection and diagnoses can be used as part of the test of any UUT that uses this bus. Additionally, parts of the test set may be reused for testing another high-speed I/O. It is reasonable to utilize some of the test routines used in a USB 3.0 test, in the development of a USB 3.1 (running at 10 Gbps), even if the latter has substantial differences in protocol. Many of the SI developed for one protocol can be reused as is, while other SIs may need to undergo modifications before reuse. The modifications will likely take less time and effort than starting from scratch. This paper illustrates an example of high-speed I/O testing, generalizes failure modes that are likely to occur in high-speed I/O, and offers a strategy for testing them with SIs within FPGAs. This strategy offers several advantages besides reusability, including tester proximity to the UUT, test modularization, standardization approaching an ATE-agnostic test development process, overcoming physical limitations of general-purpose test instruments, and utilization of specific-purpose test instruments. Additionally, test instrument obsolescence can be overcome by upgrading to ever-faster and larger FPGAs without losing any previously developed design effort. With SIs and tests scalable and upward compatible, the test engineer need not start test development for high-speed I/O from scratch, which will substantially reduce time and effort.
Technical Library | 2019-04-08 23:21:29.0
Climatest Symor® adopts molecular sieve to dry air, the whole system is controlled by microcomputer, when humidity is high, It will start to absorb moisture,when the humidity reach the pre-set value, it will stop absorbing, and then discharge the water to outside the cabinet by heating,again and again by automatic control. The most effective and environment-friendly moisture-absorbing desiccant is molecular sieve, molecular sieve is the microporous crystal material synthesized by silicon and aluminium oxide. In order to keep the crystal net discharge to be zero, atoms with cations are located in the crystal structure.and the cation used in these synthetic crystals is usually sodium. At present, there are two kinds of molecular sieves widely used in the dry box industry: Class A and Class X. Molecular sieves are synthesized, shaped and activated under strictly controlled production processes. The whole controlled sythesis process can ensure consistency of the three-dimensional pore size. 3A molecular sieve pore size is 3 angstroms, 4A molecular sieve pore size is 4 angstroms; 13X molecular sieve pore size is 8.5 angstroms. The working principle of molecular sieve: Molecular sieves adsorb molecules onto the crystal surface by physical attraction force. Since 95% surface area of the molecular sieve is within aperture,it needs to screen the adjacent molecules by different size. Only small size molecules can enter into the inner adsorption surface of the molecular sieve through the crystal aperture. This selective adsorption phenomenon is called molecular sieve effect. The molecular sieve adsorption capacity and charge density (polarity) are further related to the adsorbed molecules. The molecular sieves can further distinguish which of the mixed molecules can be adsorbed and determine to what extent the charge density can allow the molecules to be adsorbed onto the crystal. Water molecules are particularly small (2.6 angstroms), that belong to highly polar molecules (very strong positive and negative electron density), and are easily adsorbed by molecular sieves, even under very low moisture condition,once the water molecules are adsorbed,they will be firmly fixed on the crystal. The environment-friendly moisture absorption device is equipped with molecular sieve. When it’s absorbing, the memory alloy controller is in tensile state, and the spring is in contractive state,which just make the valve contact the outer baffle, this insulates the outside air from inside dry box air to achieve dehumidification purpose; and after molecular sieve absorbed moisture inside dry box and become saturated, the program will automatically control the memory alloy device to shrink it so that the valve reaches the inner baffle position. Meanwhile, due to the shrinkage of the memory alloy, the spring is stretched and the valve is pulled out of the outer baffle,so that the moisture in molecular sieve will be discharged into the outside. after the dehumidifying process finished, the program automatically control and reset the memory alloy and spring,to restart absorbing status.
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