PIC32MX795F512LT-80ISLASHPF datasheet(43/256 Pages) MICROCHIP

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DS61156G-page 43

PIC32MX5XX/6XX/7XX

2.0

GUIDELINES FOR GETTING

STARTED WITH 32-BIT

MICROCONTROLLERS

2.1

Basic Connection Requirements

Getting started with the PIC32MX5XX/6XX/7XX family

of 32-bit Microcontrollers (MCUs) requires attention to

a minimal set of device pin connections before pro-

ceeding with development. The following is a list of pin

names, which must always be connected:

• All VDD and VSS pins

(see Section 2.2 “Decoupling Capacitors”)

• All AVDD and AVSS pins even if the ADC module is

not used

(see Section 2.2 “Decoupling Capacitors”)

•VCAP/VCORE pin

(see Section 2.3 “Capacitor on Internal Voltage

Regulator (VCAP/VCORE)”)

•MCLR pin

(see Section 2.4 “Master Clear (MCLR) Pin”)

• PGECx/PGEDx pins used for In-Circuit Serial

Programming™ (ICSP™) and debugging

purposes

(see Section 2.5 “ICSP Pins”)

• OSC1 and OSC2 pins when external oscillator

source is used

(see Section 2.8 “External Oscillator Pins”)

The following pin may be required, as well:

VREF+/VREF- pins used when external voltage reference

for ADC module is implemented

2.2

Decoupling Capacitors

The use of decoupling capacitors on power supply

pins, such as VDD, VSS, AVDD and AVSS is required.

See Figure 2-1.

Consider the following criteria when using decoupling

capacitors:

• Value and type of capacitor: A value of 0.1 µF

(100 nF), 10-20V is recommended. The capacitor

should be a low Equivalent Series Resistance

(low-ESR) capacitor and have resonance fre-

quency in the range of 20 MHz and higher. It is

further recommended to use ceramic capacitors.

• Placement on the printed circuit board: The

decoupling capacitors should be placed as close

to the pins as possible. It is recommended that

the capacitors be placed on the same side of

the board as the device. If space is constricted,

the capacitor can be placed on another layer on

the PCB using a via; however, ensure that the

trace length from the pin to the capacitor is

within one-quarter inch (6 mm) in length.

• Handling high frequency noise: If the board is

experiencing high frequency noise, upward of

tens of MHz, add a second ceramic-type capacitor

in parallel to the above described decoupling

capacitor. The value of the second capacitor can

be in the range of 0.01 µF to 0.001 µF. Place this

second capacitor next to the primary decoupling

capacitor. In high-speed circuit designs, consider

implementing a decade pair of capacitances as

close to the power and ground pins as possible.

For example, 0.1 µF in parallel with 0.001 µF.

• Maximizing performance: On the board layout

from the power supply circuit, run the power and

return traces to the decoupling capacitors first,

and then to the device pins. This ensures that the

decoupling capacitors are first in the power chain.

Equally important is to keep the trace length

between the capacitor and the power pins to a

minimum, thereby reducing PCB track

inductance.

Note 1: This data sheet summarizes the features

of the PIC32MX5XX/6XX/7XX family of

devices. It is not intended to be a

comprehensive reference source. To

complement the information in this data

sheet, refer to the related section of the

“PIC32 Family Reference Manual”, which

is available from the Microchip web site

(www.microchip.com/PIC32).

2: Some registers and associated bits

described in this section may not be

available on all devices. Refer to

Section 4.0 “Memory Organization” in

this data sheet for device-specific register

and bit information.

Note:

The AVDD and AVSS pins must be

connected, regardless of the ADC use

and the ADC voltage reference source.

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