EM78P417N/418N/419N
8-Bit Microprocessor with OTP ROM
Internal RC Drift Rate (Ta=25℃, VDD=5V±5%, VSS=0V)
Drift Rate
Internal
RC Frequency
Temperature
(-40℃~+80℃)
Voltage
Process
Total
(2.3V~5.5V)
4MHz
8MHz
±10%
±10%
±10%
±10%
±5%
±6%
±5%
±5%
±4%
±4%
±4%
±4%
±19%
±20%
±19%
±19%
1MHz
455MHz
Theoretical values are for reference only. Actual values may vary depending on actual process.
6.12 Power-on Considerations
Any microcontroller is not warranted to start operating properly before the power supply
stabilizes in steady state. EM78P417/8/9N is equipped with Power On Voltage
Detector (POVD) with detection level range of 1.9V to 2.1V. The circuitry eliminates the
extra external reset circuit. It will work well if Vdd rises quickly enough (50 ms or less).
However, under critical applications, extra devices are still required to assist in solving
power-on problems.
6.12.1 External Power-on Reset Circuit
The circuit shown in the
VDD
following figure implements
an external RC to produce a
/RESET
R
C
D
reset pulse. The pulse
width (time constant) should
be kept long enough to
EM78P417/ 8/ 9N
Rin
allow Vdd to reach the
minimum operating voltage.
This circuit is used when the
power supply has a slow
power rise time. Because
Fig. 6-18 External Power on Reset Circuit
the current leakage from the /RESET pin is about ±5µA, it is recommended that R
should not be great than 40 K. This way, the voltage at Pin /RESET is held below 0.2V.
The diode (D) acts as a short circuit at power-down. The “C” capacitor is discharged
rapidly and fully. Rin, the current-limited resistor, prevents high current discharge or
ESD (electrostatic discharge) from flowing into Pin /RESET.
60 •
Product Specification (V1.0) 06.23.2005
(This specification is subject to change without further notice)
ELAN [ ELAN MICROELECTRONICS CORP ]
