參數(shù)資料
型號： UPD17246MC-xxx-5A4
廠商： NEC Corp.
英文描述： 4-BIT SINGLE-CHIP MICROCONTROLLERS FOR SMALL GENERAL-PURPOSE INFRARED REMOTE CONTROL TRANSMITTERS
中文描述： 4位單片微控制器的小型通用兩用紅外遙控遞質(zhì)
文件頁數(shù)： 56/102頁
文件大?。?/td> 461K
代理商： UPD17246MC-XXX-5A4
56
Data Sheet U15002EJ1V0DS
μ
PD17240, 17241, 17242, 17243, 17244, 17245, 17246
5.3.2
Countermeasures against noise during transmission (carrier output)
When a signal is transmitted from the transmitter of a remote controller, a peak current of 0.5 to 1 A may flow through
the infrared LED. Since two batteries are usually used as the power source of the transmitter, several
of equivalent
resistance (r) exists in the power source as shown in Figure 5-2. This resistance increases to 10 to 20
if the supply
voltage drops to 2 V. While the carrier is being output from the REM pin (while the infrared LED lights), therefore,
a high-frequency noise may be generated on the power lines due to the voltage fluctuation that may take place
especially during switching.
To minimize the influence on the microcontroller of this high-frequency noise, take the following measures.
<1>
Separate the power lines of the microcontroller from the power lines of the infrared LED with the terminals
of the batteries at the center. Use thick power lines and keep the wiring short.
Locate the resonator as close as possible to the microcontroller and shield it with GND lines (as indicated
by the shaded portion in the figure below).
Locate the capacitor for stabilization of the power supply closely to the power lines of the microcontroller.
Also, use a capacitor to eliminate high-frequency noise.
To prevent data from changing, do not execute data read/write processing such as key scan, an interrupt
that requires a stack, or the CALL/RET instruction, while the carrier is being output.
To improve the reliability in case of program hang-up, use the watchdog timer.
<2>
<3>
<4>
<5>
Figure 5-2. Example of Countermeasures Against Noise
0.5 to 1 A
Infrared LED
REM
V
DD
Microcontroller
+
–
r
Batteries
V
SS
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