PIC24FJ128GA MICROCHIP [Microchip Technology], PIC24FJ128GA Datasheet - Page 187

• Manufacturer Part Number: PIC24FJ128GA
• Description: General Purpose, 16-Bit Flash Microcontrollers
• Manufacturer: MICROCHIP [Microchip Technology]

23.2
All of the PIC24FJ128GA family devices power their
core digital logic at a nominal 2.5V. This may create an
issue for designs that are required to operate at a
higher typical voltage, such as 3.3V. To simplify system
design, all devices in the PIC24FJ128GA family incor-
porate an on-chip regulator that allows the device to
run its core logic from V
The regulator is controlled by the ENVREG pin. Tying
V
vides power to the core from the other V
the regulator is enabled, a low ESR capacitor (such as
tantalum) must be connected to the V
(Figure 23-1). This helps to maintain the stability of the
regulator. The recommended value for the filer capacitor
is provided in Section 26.1 “DC Characteristics”.
If ENVREG is tied to V
this case, separate power for the core logic at a nomi-
nal 2.5V must be supplied to the device on the
V
levels, typically 3.3V. Alternatively, the V
and V
nominal voltage. Refer to Figure 23-1 for possible
configurations.
23.2.1
When the voltage regulator is enabled, it takes approxi-
mately 20 μs for it to generate output. During this time,
designated as T
T
operation after any power-down, including Sleep mode.
If the regulator is disabled, a separate Power-up Timer
(PWRT) is automatically enabled. The PWRT adds a
fixed delay of 64 ms nominal delay at device start-up.
23.2.2
When
PIC24FJ128GA family devices also have a simple
brown-out capability. If the voltage supplied to the reg-
ulator is inadequate to maintain a regulated level, the
regulator Reset circuitry will generate a Brown-out
Reset. This event is captured by the BOR flag bit
(RCON<0>). The brown-out voltage levels are specific
in Section 26.1 “DC Characteristics”.
23.2.3
The on-chip regulator is designed to meet the power-up
requirements for the device. If the application does not
use the regulator, then strict power-up conditions must
be adhered to. While powering up, V
never exceed V
© 2006 Microchip Technology Inc.
STARTUP
DD
DDCORE
to the pin enables the regulator, which in turn, pro-
DD
On-Chip Voltage Regulator
pins can be tied together to operate at a lower
/V
the
is applied every time the device resumes
CAP
ON-CHIP REGULATOR AND POR
ON-CHIP REGULATOR AND BOR
POWER-UP REQUIREMENTS
pin to run the I/O pins at higher voltage
DD
STARTUP
on-chip
by 0.3 volts.
SS
DD
, code execution is disabled.
, the regulator is disabled. In
.
regulator
DDCORE
DD
is
DDCORE
DDCORE
pins. When
/V
enabled,
CAP
/V
must
CAP
Preliminary
pin
PIC24FJ128GA FAMILY
FIGURE 23-1:
Note 1:
Regulator Enabled (ENVREG tied to V
Regulator Disabled (ENVREG tied to ground):
Regulator Disabled (V
(10 μF typ)
2.5V
C
2.5V
EFC
(1)
These are typical operating voltages. Refer
to Section 26.1 “DC Characteristics” for
the full operating ranges of V
V
(1)
DDCORE
3.3V
3.3V
.
CONNECTIONS FOR THE
ON-CHIP REGULATOR
(1)
V
ENVREG
V
V
DD
DDCORE
SS
DD
PIC24FJ128GA
V
ENVREG
V
V
V
ENVREG
V
V
DD
DDCORE
SS
DD
DDCORE
SS
tied to V
PIC24FJ128GA
PIC24FJ128GA
/V
CAP
DS39747C-page 185
/V
/V
DDCORE
CAP
CAP
DD
and
DD
):
):