Datasheet

© 2009-2012 Microchip Technology Inc. Preliminary DS70616F-page 31
dsPIC33EPXXX(GP/MC/MU)806/810/814 and PIC24EPXXX(GP/GU)810/814
2.0 GUIDELINES FOR GETTING
STARTED WITH 16-BIT
DIGITAL SIGNAL
CONTROLLERS AND
MICROCONTROLLERS
2.1 Basic Connection Requirements
Getting started with the 16-bit DSCs and microcontrollers
requires attention to a minimal set of device pin
connections before proceeding with development. The
following is a list of pin names, which must always be
connected:
• All V
DD and VSS pins (see Section 2.2
“Decoupling Capacitors”)
• All AVDD and AVSS pins (regardless if ADC module
is not used) (see Section 2.2 “Decoupling
Capacitors”)
•V
CAP (see Section 2.3 “CPU Logic Filter
Capacitor Connection (V
CAP)”)
•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 2.6 “External
Oscillator Pins”)
Additionally, the following pins may be required:
•V
USB3V3 pin is used when utilizing the USB
module. If the USB module is not used, V
USB3V3
must be connected to V
DD.
•V
REF+/VREF- pin is used when external voltage
reference for ADC module is implemented
2.2 Decoupling Capacitors
The use of decoupling capacitors on every pair of
power supply pins, such as V
DD, VSS, VUSB3V3,
AVDD and AVSS is required.
Consider the following criteria when using decoupling
capacitors:
• Value and type of capacitor: Recommendation of
0.1 µF (100 nF), 10-20V. This capacitor should be a
low-ESR and have resonance frequency in the
range of 20 MHz and higher. It is 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 to place the
capacitors 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, above tens of
MHz, add a second ceramic-type capacitor in paral-
lel 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 decou-
pling 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
dsPIC33EPXXX(GP/MC/MU)806/810/81
4 and PIC24EPXXX(GP/GU)810/814
families 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
“dsPIC33E/PIC24E Family Reference
Manual”, which is available from the
Microchip web site (www.microchip.com)
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 AV
DD and AVSS pins must be
connected independent of the ADC
voltage reference source. The voltage
difference between AV
DD and VDD cannot
exceed 300 mV at any time during
operation or start-up.