em78p257 ELAN Microelectronics Corp, em78p257 Datasheet - Page 51

• Manufacturer Part Number: em78p257
• Description: 8-bit Microcontroller
• Manufacturer: ELAN Microelectronics Corp

This specification is subject to change without prior notice.
3. Residue-Voltage Protection
(D) acts as a short circuit at the moment of power down. The capacitor C will discharge rapidly and fully. Rin, 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 on reset. Fig.23 and Fig.24
show how to b uild a residue-voltage protection circuit
E M 7 8 P 2 5 7 A / B
E M 7 8 P 2 5 7 A / B
/ R E S E T
/ R E S E T
Fig. 23 Circuit 1 for the residue voltage protection
V d d
V d d
Fig. 22 External Power on Reset Circuit
1 0 0 K
Q 1
51
R i n
1 N 4 6 8 4
1 0 K
R
C
3 3 K
D
V d d
EM78P257
07.27.2004 (V1.4)
OTP ROM