Цитата(TigerSHARC @ Feb 19 2015, 18:15)
Буду рад если кто-то объяснит мне смысл сих знаков на плате?
Источники опорного напряжения чувствительны к механическим напряжениям, которые передаются на кристалл от печатной платы через выводы. Чтобы уменьшить влияние механических стрессов, изготовители ИОН рекомендуют максимально изолировать ИОН от остальной платы, в том числе - при помощи вырезов в плате. В данном случае мы видим неплохую подвеску, выполненную из материала печатной платы. Хм, надо будет взять на вооружение.
PS: LT
AN82 - Understanding and Applying Voltage References, page 6-7:
Stress has a directly measurable effect on reference output. If the stress changes over a period of time, it may manifest itself as unacceptable long-term drift. Circuit boards are not perfectly elastic, so bending forces may cause permanent deformation and a permanent step-change in reference output voltage. Devices in metal (TO-5 and TO-46) packages are largely immune to board stress, owing to the rigidity of the package and the flexibility of the leads. Plastic and surface mount packages are another matter.
Board stress effects are easily observed by monitoring the output of a reference while applying a bending force to the board. A controlled experiment was performed to measure the effect of board stress on an LT1460CS8-2.5 surface mount reference. Devices were mounted in the center of 7" x 9" rectangular boards, as shown in Figure 11. The boards were then deflected out-of-plane 18 mils per
inch, as shown in steps 1 through 4. Figure 12 shows the net effect on the output of one representative sample measured over eight cycles of flexure.
The original board showed about 60ppm peak-to-peak shift. The board was then slotted on a vertical mill, forming a 0.5" x 0.5" tab with the reference located in its center (also illustrated in Figure 11). The test continued with the slotted configuration, and the output voltage variations were reduced to ±1 count (10µV) on the meter, or approximately 4ppm peak-to-peak. This represents a tenfold
improvement in stress-induced output voltage shift.
хитрые приёмы разводки прецизионных цепей, на примере ИОН для Fluke 8508A
Feb 19 2015, 07:45
