1999 Microchip Technology Inc.
DS30561B-page 61
PIC12C67X
FIGURE 9-10: EXTERNAL POWER-ON
RESET CIRCUIT (FOR SLOW
VDD POWER-UP)
Note 1: External Power-on Reset circuit is required only
if VDD power-up slope is too slow. The diode D
helps discharge the capacitor quickly when VDD
powers down.
2: R < 40 k
is recommended to make sure that
voltage drop across R does not violate the
device’s electrical specification.
3: R1 = 100
to 1 k will limit any current flowing
into MCLR from external capacitor C, in the
event of MCLR/VPP pin breakdown due to
Electrostatic Discharge (ESD) or Electrical
Overstress (EOS).
C
R1
R
D
VDD
MCLR
PIC12C67X
FIGURE 9-11: EXTERNAL BROWN-OUT
PROTECTION CIRCUIT 1
FIGURE 9-12: EXTERNAL BROWN-OUT
PROTECTION CIRCUIT 2
Note 1:
This circuit will activate reset when VDD goes
below (Vz + 0.7V), where Vz = Zener voltage.
2: Resistors should be adjusted for the character-
istics of the transistor.
VDD
33k
10k
4.3k
VDD
MCLR
PIC12C67X
Note 1:
This brown-out circuit is less expensive,
albeit less accurate. Transistor Q1 turns off
when VDD is below a certain level such that:
2: Resistors should be adjusted for the charac-
teristics of the transistor.
VDD
R1
R1 + R2
= 0.7V
VDD
R2
4.3k
PIC12C67X
R1
Q1
VDD
MCLR