em78p210n ELAN Microelectronics Corp, em78p210n Datasheet - Page 51

• Manufacturer Part Number: em78p210n
• Description: 8-bit Microcontroller With Otp Rom
• Manufacturer: ELAN Microelectronics Corp

Product Specification (V1.2) 04.22.2008
(This specification is subject to change without further notice)
6.8.4
The EM78P210N offers a versatile internal RC mode with default frequency value of
4MHz. Internal RC oscillator mode has other frequencies (1 MHz, 16 MHz, and
455kHz) that can be set by Code Option (Word 1), RCM1, and RCM0. The Table below
describes the EM78P210N internal RC drift with the variations on voltage, temperature,
and process.
Internal RC Drift Rate (Ta=25 ° C, VDD=5.0V ± 5%, VSS=0V)
Theoretical values are for reference only. Actual values may vary depending on actual process.
6.9 Power-on Considerations
Any microcontroller is not warranted to start operating properly before the power supply
stabilizes to a steady state. EM78P210N has a built-in Power-on Voltage Detector
(POVD) with detection level range of 1.7V to 1.9V. 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.
6.9.1
The circuit shown in the
figure implements an
external RC to produce a
reset pulse. The pulse
width (time constant) should
be kept long enough to
allow Vdd to reach the
minimum operating voltage.
This circuit is used when the
power supply has a slow
power rise time. Since the
current leakage from the /RESET pin is about ±5μA, it is recommended that R should
not be greater than 40K. This way, the voltage at Pin /Reset is held below 0.2V. The
diode (D) functions 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.
RC Frequency
Internal
455kHz
16MHz
4MHz
1MHz
Internal RC Oscillator Mode
External Power-on Reset Circuit
(-40°C~+85°C)
Temperature
±5%
±5%
±5%
±5%
(2.1V~5.5V)
Voltage
Figure 6-17 External Power on Reset Circuit
±5%
±5%
±5%
±5%
/RESET
VDD
Drift Rate
8-Bit Microcontroller with OTP ROM
Process
±4%
±4%
±4%
±4%
Rin
C
R
EM78P210N
±14%
±14%
±14%
±14%
Total
D
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