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TODX298 Datasheet(PDF) 8 Page - Toshiba Semiconductor |
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TODX298 Datasheet(HTML) 8 Page - Toshiba Semiconductor |
8 / 10 page TODX298 2001-07-26 8 7. Precaution on Use (1) Maximum rating The maximum ratings are the limit values which must not be exceeded during operation of device. None of these rating value must not be exceeded. If the maximum rating value is exceeded, the characteristics of devices may never be restored properly. In extreme cases, the device may be permanently damages. (2) Lifetime of light emitters If an optical module is used for a long period of time, degeneration in the characteristics will mostly be due to a lowering of the fiber output power (Pf). This is caused by the degradation of the optical output of the LEDs used as the light source. The cause of degradation of the optical output of the LEDs may be defects in wafer crystallization or mold resin stress. The detailed causes are, however, not clear. The lifetime of light emitters is greatly influenced by the operating conditions and the environment in which it is used as well as by the lifetime characteristics unique to the device type. Thus, when a light emitting device and its operating conditions determined, Toshiba recommend that lifetime characteristics be checked. Depending on the environment conditions, Toshiba recommend that maintenance such as regular checks of the amount of optical output in accordance with the condition of operating environment. (3) Soldering Optical modules are comprised of internal semiconductor devices. However, in principle, optical modules are optical components. During soldering, ensure that flux does not contact with the emitting surface or the detecting surface. Also ensure that proper flux removal is conducted after soldering. Some optical modules come with a protective cap. The protective cap is used to avoid malfunction when the optical module is not in use. Note that it is not dust or waterproof. As mentioned before, optical modules are optical components. Thus, in principle, soldering where there may be flux residue and flux removal after soldering is not recommended. Toshiba recommend that soldering be performed without the optical module mounted on the board. Then, after the board has been cleaned, the optical module should be soldered on to the board manually. If the optical module cannot be soldered manually, use non−halogen (chlorine−free) flux and make sure, without cleaning, there is no residue such as chlorine. This is one of the ways to eliminate the effects of flux. In such a cases, be sure to check the devices’ reliability. (4) Noise resistance It is believed that the use of optical transfer devices improve noise resistance. In theory, optical fiber is not affected by noise at all. However, receiving modules which handle signals whose level is extremely small, are susceptible to noise. TOSLINK improve noise resistance to use a conductive case. However, the current signal output by the optical receiving modules’ photodiode is extremely small. Thus, in some environments, shielding the case may not achieve sufficient noise resistance. First systems which incorporate TOSLINK, Toshiba recommend testing using the actual device to check its noise resistance. Use a simple noise filter on TOSLINK fiber optic transceiving module’s power line. If the ripple in the power supply used is significant, reinforce the filter. The optical module is to be used in an area which is susceptible to radiated noise, increase the shielding by covering the optical module and the power line filter with a metallic cover. (5) Vibration and shock This module is plastic sealed and has its wire fixed by resin. This structure is relatively resistant to vibration and shock. In actual equipment, there are sometime cases in which vibration, shock, or stress is applied to soldered parts or connected parts, resulting in lines cut. A care must be taken in the design of equipment which will be subject to high levels of vibration. (6) Fixing fiber optical transceiving module Solder the fixed pin (pins 9 and 10) of fiber optic transceiving module TODX298 to the printed circuit board to fix the module to the board. (7) Shielding and wiring pattern of fiber optic transceiving modules To shield, connect the fixed pins (pins 9 and 10) of fiber optic transceiving module TODX298 to the GND. Where the fiber optic transceiving module uses conductive resin, be careful that the case does not touch wiring (including land). To improve noise resistance, shield the optical module and the power line filter using a metallic cover. |
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