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MB90550A/550B Series
16
5.
Crystal Oscillator Circuit
Noises around X0 or X1 pins may cause abnormal operations. Make sure to provide bypass capacitors via
shortest distance from X0, X1 pins, crystal oscillator (or ceramic resonator) and ground lines, and make sure
that lines of oscillation circuit not cross the lines of other circuits.
A printed circuit board artwork surrounding the X0 and X1 pins with grand area for stabilizing the operation is
highly recommended.
Turning-on Sequence of Power Supply to A/D Converter and Analog Inputs
6.
Make sure to turn on the A/D converter power supply, D/A converter power supply (AV
CC
, AVRH, AVRL) and
analog inputs (AN0 to AN7) after turning-on the digital power supply (V
CC
).
Turn-off the digital power after turning off the A/D converter supply and analog inputs. In this case, make sure
that the voltage does not exceed AVRH or AV
CC
(turning on/off the analog and digital power supplies simulta-
neously is acceptable).
Connection of Unused Pins of A/D Converter
7.
Connect unused pin of A/D converter to AV
CC
= V
CC
, AV
SS
= AVRH = AVRL = V
SS
.
N.C. Pin
8.
The N.C. (internally connected) pin must be opened for use.
Notes on Energization
9.
To prevent the internal regulator circuit from malfunctioning, set the voltage rise time during energization at 50
μ
s or more.
10. Indeterminate outputs from ports 0 and 1
The outputs from ports 0 and 1 become indeterminate during oscillation setting time of step-down circuit (during
a power-on reset) after the power is turned on. (MB90552A, MB90552B, MB90553A, MB90553B, MB90F553A,
MB90V550A)
The series without built-in step-down circuit has no oscillation setting time of step-down circuit, so outputs should
not become indeterminate. (MB90P553A)
Oscillation setting time *
2
V
CC
(power-supply pin)
PONR (power-on reset) signal
RST (external asynchronous reset) signal
RST (internal reset) signal
Oscillation clock signal
KA (internal operating clock A) signal
KB (internal operating clock B) signal
PORT (port output) signal
Step-down circuit setting time *
1
Period of indeterminate
*1: Step-down circuit setting time 2
17
/oscillation clock frequency (oscillation clock frequency of 16 MHz: 8.19 ms)
*2: Oscillation setting time
2
18
/oscillation clock frequency (oscillation clock frequency of 16 MHz: 16.38 ms)
Timing chart of indeterminate outputs from ports 0 and 1