PIC16F627A_05 Datasheet, PDF (108/180 Pages) Microchip Technology – Flash-Based, 8-Bit CMOS Microcontrollers with nanoWatt Technology

PIC16F627A/628A/648A
FIGURE 14-11:
VDD
VDD
EXTERNAL POWER-ON
RESET CIRCUIT (FOR
SLOW VDD POWER-UP)
D
R
PIC16F627A/628A/648A
R1
MCLR
C
Note 1:
2:
3:
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.
R < 40 kΩ is recommended to make sure
that voltage drop across R does not violate
the device’s electrical specification.
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).
FIGURE 14-12:
VDD
33k
EXTERNAL BROWN-OUT
PROTECTION CIRCUIT 1
VDD
10k
MCLR
40k _{PIC16F627A/628A/648A}
FIGURE 14-13:
VDD
R1
R2
EXTERNAL BROWN-OUT
PROTECTION CIRCUIT 2
VDD
Q1
MCLR
40k _{PIC16F627A/628A/648A}
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:
R1
VDD x
= 0.7 V
R1 + R2
R1
2: IdnistearbnlxaeldBwrohwennR-u1osu+itnRRg _{2ethsies=t cs0ihr.c7ouuVitld.} be
3: Resistors should be adjusted for the
characteristics of the transistor.
Note 1: This circuit will activate Reset when VDD
goes below (Vz + 0.7V) where Vz = Zener
voltage.
2: Internal Brown-out Reset circuitry should
be disabled when using this circuit.
DS40044D-page 106
© 2005 Microchip Technology Inc.