16F628 datasheet(105/168 Pages) MICROCHIP

105 / 168 page

 2002 Microchip Technology Inc.

Preliminary

DS40044A-page 103

PIC16F627A/628A/648A

FIGURE 14-11:

EXTERNAL POWER-ON

RESET CIRCUIT (FOR

SLOW VDD POWER-UP)

FIGURE 14-12:

EXTERNAL BROWN-OUT

PROTECTION CIRCUIT 1

FIGURE 14-13:

EXTERNAL BROWN-OUT

PROTECTION CIRCUIT 2

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 k

Ω is recommended to make sure

that voltage drop across R does not violate

the device’s electrical specification.

3: R1 = 100

Ω to 1 kΩ will limit any current

flowing into MCLR from external capacitor

C in the event of MCLR/V

PP pin breakdown

due to Electrostatic Discharge (ESD) or

Electrical Overstress (EOS).

MCLR

PIC16F627A/628A/648A

Note

1: This circuit will activate RESET when V

goes below (Vz + 0.7V) where Vz = Zener

voltage.

2: Internal Brown-out Reset circuitry should

be disabled when using this circuit.

33k

10k

40k

MCLR

PIC16F627A/628A/648A

Vdd x

R1 + R2

= 0.7 V

40k

MCLR

PIC16F627A/628A/648A

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 Reset should be dis-

abled when using this circuit.

3: Resistors should be adjusted for the charac-

teristics of the transistor.

DD x

R1 + R2

= 0.7 V

16F628 Datasheet(PDF) 105 Page - Microchip Technology

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