PIC18LF24K Datasheet, PDF (18/594 Pages) –

PIC18(L)F26/45/46K40
2.0 GUIDELINES FOR GETTING
STARTED WITH
PIC18(L)F26/45/46K40
MICROCONTROLLERS
2.1 Basic Connection Requirements
Getting started with the PIC18(L)F26/45/46K40 family
of 8-bit microcontrollers requires attention to a minimal
set of device pin connections before proceeding with
development.
The following pins must always be connected:
• All VDD and VSS pins (see Section 2.2 “Power
Supply Pins”)
• MCLR pin (see Section 2.3 “Master Clear (MCLR)
Pin”)
These pins must also be connected if they are being
used in the end application:
• PGC/PGD pins used for In-Circuit Serial
Programming™ (ICSP™) and debugging purposes
(see Section 2.4 “ICSP™ Pins”)
• OSCI and OSCO pins when an external oscillator
source is used (see Section 2.5 “External
Oscillator Pins”)
Additionally, the following pins may be required:
• VREF+/VREF- pins are used when external voltage
reference for analog modules is implemented
The minimum mandatory connections are shown in
Figure 2-1.
FIGURE 2-1:
RECOMMENDED
MINIMUM CONNECTIONS
VDD
C2
Rev. 10-000249A
9/1/2015
R1
R2
MCLR
C1
PIC18(L)Fxxxxx
Vss
Key (all values are recommendations):
C1 and C2 : 0.1 PF, 20V ceramic
R1: 10 kΩ
R2: 100Ω to 470Ω
2.2 Power Supply Pins
2.2.1 DECOUPLING CAPACITORS
The use of decoupling capacitors on every pair of
power supply pins (VDD and VSS) is required.
Consider the following criteria when using decoupling
capacitors:
• Value and type of capacitor: A 0.1 F (100 nF),
10-20V capacitor is recommended. The capacitor
should be a low-ESR device, with a resonance
frequency in the range of 200 MHz and higher.
Ceramic capacitors are recommended.
• 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 no greater
than 0.25 inch (6 mm).
• Handling high-frequency noise: If the board is
experiencing high-frequency noise (upward of
tens of MHz), add a second ceramic type capaci-
tor in parallel to the above described decoupling
capacitor. The value of the second capacitor can
be in the range of 0.01 F to 0.001 F. Place this
second capacitor next to each 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
(e.g., 0.1 F in parallel with 0.001 F).
• 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 trace
inductance.
2.2.2 TANK CAPACITORS
On boards with power traces running longer than
six inches in length, it is suggested to use a tank capac-
itor for integrated circuits, including microcontrollers, to
supply a local power source. The value of the tank
capacitor should be determined based on the trace
resistance that connects the power supply source to
the device, and the maximum current drawn by the
device in the application. In other words, select the tank
capacitor so that it meets the acceptable voltage sag at
the device. Typical values range from 4.7 F to 47 F.
 2016 Microchip Technology Inc.
Preliminary
DS40001816C-page 18