PIC32MX5XX_11 Datasheet, PDF (43/256 Pages) Microchip Technology – High-Performance, USB, CAN and Ethernet 32-bit Flash Microcontrollers

PIC32MX5XX/6XX/7XX
2.0 GUIDELINES FOR GETTING
STARTED WITH 32-BIT
MICROCONTROLLERS
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.
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
Note:
The AVDD and AVSS pins must be
connected, regardless of the ADC use
and the ADC voltage reference source.
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.
© 2009-2011 Microchip Technology Inc.
DS61156G-page 43