PIC16F627A Datasheet, PDF (105/168 Pages) Microchip Technology – FLASH-Based 8-Bit CMOS Microcontrollers

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: 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 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 breakdown
due to Electrostatic Discharge (ESD) or
Electrical Overstress (EOS).
FIGURE 14-12:
VDD
33k
10k
EXTERNAL BROWN-OUT
PROTECTION CIRCUIT 1
VDD
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: IanbtelerdnVawdl _{hdBerxnowunsR-in1ogu+tthRRis2esceir=tcsu0hi.to7.} uVld be dis-
3: Resistors should be adjusted for the charac-
teristics 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.
 2002 Microchip Technology Inc.
Preliminary
DS40044A-page 103