EM78P468NBQ EMC [ELAN Microelectronics Corp], EM78P468NBQ Datasheet - Page 42

• Manufacturer Part Number: EM78P468NBQ
• Description: 8-BIT Microcontroller
• Manufacturer: EMC [ELAN Microelectronics Corp]

EM78P468N
8-BIT Microcontroller
38 •
4.7 Power-on Considerations
4.7
4.7
.1
.2
Any microcontroller (as with this LSI) is not warran
the power supply stabilizes in
(POR)
external reset circuit but will work well
less). However, under critical applicat
solving p
This circuit implements an external RC to produc
width (time constant) should be kept long enough to allow VDD to reach minimum
operation voltage. This circuit is used when the po
the current leakage from the /RESET pin is about ±
not be great than 40K. In this way, the voltage at Pin /RESET is held below 0.2V. The
diode (D) acts as a short circuit at power-down. The capacitor, C, is discharg
and fully. Rin, the current-limited r
(ele trostatic discharge) from flowing into Pin /RESET.
When battery is replaced, device power (VDD) is disconnected but residue-voltage
remains. The residue-voltage may trips below minimum VDD, but above zero. This
condition may cause poor power on reset. Fig.13 and Fig.14 show how to build a
residue-voltage protection circuit
c
External Power-on Rese
Residue-Voltage Protection
with detection level ran
ower-on problems.
Fig. 13
Fig. 12 External Power on Reset Circuit
Circuit 1 for the Residue Voltage
steady state. This LSI is equipped with Power On Reset
ge of 1.9V to 2.1V. The circuitry eliminates the extra
esistor, prevents high current discharge or ESD
(This specification is subject to change without further notice)
t Circuit
ions, extra devices are still required to assist in
only if the VDD rises quickly enough (50 ms or
Product Specification (V1.2) 03.15.2005
e a reset pulse (see Fig.12). The pulse
wer supply rise time is slow. Because
5µA, it is recommended that R should
ted to start operating properly before
Protection
ed rapidly