EM78P153EN EMC [ELAN Microelectronics Corp], EM78P153EN Datasheet - Page 30

• Manufacturer Part Number: EM78P153EN
• Description: EM78P153E is an 8-bit microprocessor with low-power and high-speed CMOS technology
• Manufacturer: EMC [ELAN Microelectronics Corp]

This specification is subject to change without prior notice.
4.10 Programmable Oscillator Set-Up Time
4.11 External Power 0n Reset Circuit
4.12 Residue-Voltage Protection
EM78P153E is equipped with Power On Voltage Detector (POVD) with a detecting level of 2.0 V. The
extra external reset circuit will work well if Vdd rises quick enough (50 ms or less). In many critical
applications however, extra devices are still required to assist in solving power-up problems.
The Option word contains SUT0 and SUT1, which can be used to define the oscillator set up time.
Theoretically, the range is from 4.5 ms to 72 ms. For most of crystal or ceramic resonators, the lower the
operation frequency is, the longer the Set-up time may be required. Table 12 describes the values of
Oscillator Set-Up Time.
The circuit shown in Fig 17 implements an external RC to produce the reset pulse. The pulse width (time
constant) should be kept long enough for Vdd to reach minimum operation voltage. This circuit is used
when the power supply has slow rise time. Because the current leakage from the /RESET pin is about
will be held below 0.2V. The diode (D) acts as a short circuit at the moment of power down. The
capacitor C, will discharged rapidly and fully. Rl, the current-limited resistor, will prevent high current
discharge or ESD (electrostatic discharge) from flowing to pin /RESET.
When battery is replaced, device power (Vdd) is taken off but residue-voltage remains. The
residue-voltage may trips below Vdd minimum, but not to zero. This condition may cause a poor power
5 A, it is recommended that R should not be great than 40 K. In this way, the voltage in pin /RESET
EM78P153E
/RESET
Fig. 17 External Power-Up Reset Circuit
Vdd
30
Rin
R
C
D
EM78P153E
OTP ROM
2002/03/01