PIC16C8X
FIGURE 8-13: EXTERNAL POWER-ON
RESET CIRCUIT (FOR SLOW
VDD POWER-UP)
VDD
VDD
D
R
C
R1
MCLR
PIC16CXX
Note 1: External Power-on Reset circuit is
required only if VDD power-up rate is too
slow. The diode D helps discharge the
capacitor quickly when VDD powers down.
2: R < 40 kΩ is recommended to make sure
that voltage drop across R does not exceed
0.2V (max leakage current spec on MCLR
pin is 5 µA). A larger voltage drop will
degrade VIH level on the MCLR pin.
3: R1 = 100Ω to 1 kΩ will limit any current
flowing into MCLR from external
capacitor C in the event of an MCLR pin
breakdown due to ESD or EOS.
FIGURE 8-14: BROWN-OUT PROTECTION
CIRCUIT 1
VDD
33k
VDD
10k
MCLR
40k PIC16CXX
This circuit will activate reset when VDD goes below
(Vz + 0.7V) where Vz = Zener voltage.
FIGURE 8-15: BROWN-OUT PROTECTION
CIRCUIT 2
VDD
VDD
R1
Q1
MCLR
R2
40k PIC16CXX
This brown-out circuit is less expensive, although less
accurate. Transistor Q1 turns off when VDD is below a
certain level such that:
VDD •
R1 = 0.7V
R1 + R2
DS30081F-page 46
© 1995 Microchip Technology Inc.