EM78P5840/5841/5842

8-bit Micro-controller

__________________________________________________________________________________________________________________________________________________________________

* This specification is subject to change without notice.

37

2004/11/10

V2.6

POR reset voltage is influenced in process or temperature. For some application, a constant reset voltage is

important. Next circuit will support a adjust reset voltage. By adjusting R41 and R46, POR reset voltage will be a

constant (Vpor) and the potential on /RESET pin will drop to 0 when VDD drop to below Vpor. Next plot show

the relative between VDD and Vpor. When R41 = 3.9M ohm and R46 = 910K ohm, /RESET will keep to 0 if

VDD is below 2.24V and will active after VDD upper to 2.1V.

C31

104

R42

2M2

R43

330K

S10

RESET

VDD

R44

22M

R41

3M9

RESET

Q3

C1815

Q2

C1815

R46

910K

Fig 16: External power on reset circuit 2

2.24V

2.1V

VDD

T

VDD

/RESET

Fig 17: The relative between VDD and Vpor