PIC18F87J11_12 datasheet(33/466 Pages) MICROCHIP

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 2007-2012 Microchip Technology Inc.

DS39778E-page 33

PIC18F87J11 FAMILY

2.4

Voltage Regulator Pins (ENVREG

and VCAP/VDDCORE)

The on-chip voltage regulator enable pin, ENVREG,

must always be connected directly to either a supply

voltage or to ground. Tying ENVREG to VDD enables

the regulator, while tying it to ground disables the

regulator. Refer to Section 25.3 “On-Chip Voltage

Regulator”

for details on connecting and using the

on-chip regulator.

When the regulator is enabled, a low-ESR (< 5Ω)

capacitor is required on the VCAP/VDDCORE pin to

stabilize the voltage regulator output voltage. The

VCAP/VDDCORE pin must not be connected to VDD and

must use a capacitor of 10 µF connected to ground. The

type can be ceramic or tantalum. Suitable examples of

capacitors are shown in Table 2-1. Capacitors with

equivalent specifications can be used.

Designers may use Figure 2-3 to evaluate ESR

equivalence of candidate devices.

It is recommended that the trace length not exceed

0.25 inch (6 mm). Refer to Section 28.0 “Electrical

Characteristics”

for additional information.

When the regulator is disabled, the VCAP/VDDCORE pin

must be tied to a voltage supply at the VDDCORE level.

Refer to Section 28.0 “Electrical Characteristics” for

information on VDD and VDDCORE.

Note that the “LF” versions of some low pin count

PIC18FJ parts (e.g., the PIC18LF45J10) do not have

the ENVREG pin. These devices are provided with the

voltage regulator permanently disabled; they must

always be provided with a supply voltage on the

VDDCORE pin.

FIGURE 2-3:

FREQUENCY vs. ESR

PERFORMANCE FOR

SUGGESTED VCAP

0.1

0.01

0.001

0.01

0.1

100

1000 10,000

Frequency (MHz)

Note:

Typical data measurement at 25°C, 0V DC bias.

TABLE 2-1:

SUITABLE CAPACITOR EQUIVALENTS

Make

Part #

Nominal

Capacitance

Base Tolerance

Rated Voltage

Temp. Range

TDK

C3216X7R1C106K

10 µF

±10%

16V

-55 to 125ºC

TDK

C3216X5R1C106K

10 µF

±10%

16V

-55 to 85ºC

Panasonic

ECJ-3YX1C106K

10 µF

±10%

16V

-55 to 125ºC

Panasonic

ECJ-4YB1C106K

10 µF

±10%

16V

-55 to 85ºC

Murata

GRM32DR71C106KA01L

10 µF

±10%

16V

-55 to 125ºC

Murata

GRM31CR61C106KC31L

10 µF

±10%

16V

-55 to 85ºC

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