参数资料
型号: M38049FFLWG
元件分类: 微控制器/微处理器
英文描述: 8-BIT, FLASH, 16.8 MHz, MICROCONTROLLER, PBGA64
封装: 6 X 6 MM, 0.65 MM PITCH, PLASTIC, LGA-64
文件页数: 11/129页
文件大小: 1721K
代理商: M38049FFLWG
Rev.1.00
Oct 27, 2008
Page 108 of 128
REJ03B0266-0100
3804 Group (Spec.L)
(3) Oscillator concerns
In order to obtain the stabilized operation clock on the user
system and its condition, contact the oscillator manufacturer and
select the oscillator and oscillation circuit constants. Be careful
especially when range of voltage and temperature is wide.
Also, take care to prevent an oscillator that generates clocks for a
microcomputer operation from being affected by other signals.
1. Keeping oscillator away from large current signal lines
Install a microcomputer (and especially an oscillator) as far as
possible from signal lines where a current larger than the toler-
ance of current value flows.
<Reason>
In the system using a microcomputer, there are signal lines for
controlling motors, LEDs, and thermal heads or others. When a
large current flows through those signal lines, strong noise
occurs because of mutual inductance.
2. Installing oscillator away from signal lines where potential
levels change frequently
Install an oscillator and a connecting pattern of an oscillator
away from signal lines where potential levels change fre-
quently. Also, do not cross such signal lines over the clock
lines or the signal lines which are sensitive to noise.
<Reason>
Signal lines where potential levels change frequently (such as the
CNTR pin signal line) may affect other lines at signal rising edge
or falling edge. If such lines cross over a clock line, clock wave-
forms may be deformed, which causes a microcomputer failure
or a program runaway.
Fig. 107 Wiring for a large current signal line/Wiring of
signal lines where potential levels change
frequently
(4) Analog input
The analog input pin is connected to the capacitor of a voltage
comparator. Accordingly, sufficient accuracy may not be
obtained by the charge/discharge current at the time of A/D
conversion when the analog signal source of high-impedance is
connected to an analog input pin. In order to obtain the A/D
conversion result stabilized more, please lower the impedance of
an analog signal source, or add the smoothing capacitor to an
analog input pin.
(5) Difference of memory size
When memory size differ in one group, actual values such as an
electrical characteristics, A/D conversion accuracy, and the
amount of proof of noise incorrect operation may differ from the
ideal values. When these products are used switching, perform
system evaluation for each product of every after confirming
product specification.
(6) Wiring to CNVSS pin
The CNVSS pin determines the flash memory mode.
Connect the CNVSS pin the shortest possible to the GND pattern
which is supplied to the VSS pin of the microcomputer.
In addition connecting an approximately 5 k
Ω. resistor in series
to the GND could improve noise immunity. In this case as well
as the above mention, connect the pin the shortest possible to the
GND pattern which is supplied to the VSS pin o f the
microcomputer.
Note. When the boot mode or the standard serial I/O mode is used, a
switch of the input level to the CNVSS pin is required.
Fig. 108 Wiring for the CNVSS
XIN
XOUT
VSS
M
Microcomputer
Mutual inductance
Large
current
GND
XIN
XOUT
VSS
CNTR
Do not cross
N.G.
1. Keeping oscillator away from large current signal lines
2. Installing oscillator away from signal lines where potential
levels change frequently
The shortest
CNVSS
VSS
Approx. 5k
Ω
The shortest
(Note)
Note: Shows the microcomputer’s pin.
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