Datasheet

© 2009 Microchip Technology Inc. DS39682E-page 243
PIC18F45J10 FAMILY
21.3 On-Chip Voltage Regulator
In parts designated “LF”, the microcontroller core is
powered from an external source that is separate from
V
DD. This voltage is supplied on the VDDCORE pin.
In “F” devices, a low-ESR capacitor must be connected
to the VDDCORE/VCAP pin for proper device operation.
In parts designated with an “LF” part number (i.e.,
PIC18LF45J10), power to the core must be supplied on
V
DDCORE/VCAP. It is always good design practice to
have sufficient capacitance on all supply pins.
Examples are shown in Figure 21-2.
The specifications for core voltage and capacitance
are listed inTable 24-4 of Section 24.0 “Electrical
Characteristics”.
FIGURE 21-2: CONNECTIONS FOR THE
ON-CHIP REGULATOR
21.3.1 ON-CHIP REGULATOR AND BOR
When the on-chip regulator is enabled, PIC18F45J10
family devices also have a simple brown-out capability.
If the voltage supplied to the regulator is inadequate to
maintain a regulated level, the regulator Reset circuitry
will generate a BOR Reset. This event is captured by
the BOR
flag bit (RCON<0>).
The operation of the BOR is described in more detail in
Section 5.4 “Brown-out Reset (BOR)
(PIC18F2XJ10/4XJ10 Devices Only)” and
Section 5.4.1 “Detecting BOR”. The brown-out voltage
levels are specific in Section 23.1 “DC Characteristics:
Supply Voltage”.
21.3.2 POWER-UP REQUIREMENTS
The on-chip regulator is designed to meet the power-up
requirements for the device. While powering up,
V
DDCORE must never exceed VDD by 0.3 volts.
Note: The on-chip voltage regulator is only
available in parts designated with an “F”,
such as PIC18F45J10.
Note: In parts designated with an “LF”, such as
PIC18LF45J10, V
DDCORE must never
exceed V
DD.
VDD
VDDCORE/VCAP
VSS
PIC18LFXXJ10
3.3V
2.5V
VDD
VDDCORE/VCAP
VSS
PIC18FXXJ10
CEFC
3.3V
PIC18FXXJ10 Devices (Regulator Enabled):
OR
VDD
VDDCORE/VCAP
VSS
PIC18LFXXJ10
2.5V
PIC18LFXXJ10 Devices (Regulator Disabled):