Datasheet

PIC16C7X
DS30390E-page 140  1997 Microchip Technology Inc.
FIGURE 14-13: EXTERNAL POWER-ON
RESET CIRCUIT (FOR SLOW
VDD POWER-UP)
Note 1: External Power-on Reset circuit is required
only if V
DD power-up slope is too slow. The
diode D helps discharge the capacitor
quickly when V
DD powers down.
2: R < 40 kΩ is recommended to make sure
that voltage drop across R does not violate
the device’s electrical specification.
3: R1 = 100Ω to 1 kΩ will limit any current
flowing into MCLR from external capacitor
C in the event of MCLR/
VPP pin break-
down due to Electrostatic Discharge
(ESD) or Electrical Overstress (EOS).
C
R1
R
D
V
DD
MCLR
PIC16CXX
FIGURE 14-14: EXTERNAL BROWN-OUT
PROTECTION CIRCUIT 1
FIGURE 14-15: 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: Internal brown-out detection on the
PIC16C72/73A/74A/76/77 should be dis-
abled when using this circuit.
3: Resistors should be adjusted for the char-
acteristics of the transistor.
VDD
33k
10k
40k
V
DD
MCLR
PIC16CXX
Note 1: This brown-out circuit is less expensive,
albeit less accurate. Transistor Q1 turns
off when V
DD is below a certain level
such that:
2: Internal brown-out detection on the
PIC16C72/73A/74A/76/77 should be
disabled when using this circuit.
3: Resistors should be adjusted for the
characteristics of the transistor.
V
DD •
R1
R1 + R2
= 0.7V
VDD
R2
40k
VDD
MCLR
PIC16CXX
R1
Q1