PIC32MX440F256H-80I Datasheet, PDF (578/646 Pages) Microchip Technology – 64/100-Pin General Purpose and USB 32-Bit Flash Microcontrollers

PIC32MX3XX/4XX
27.4 On-Chip Voltage Regulator
All PIC32MX3XX/4XX device’s core and digital logic
are designed to operate at a nominal 1.8V. To simplify
system designs, most devices in the
PIC32MX3XX/4XX incorporate an on-chip regulator
providing the required core logic voltage from VDD.
The internal 1.8V regulator is controlled by the
ENVREG pin. Tying this pin to VDD enables the regu-
lator, which in turn provides power to the core. A low
ESR capacitor (such as tantalum) must be connected
to the VDDCORE/VCAP pin (Figure 27-1). This helps to
maintain the stability of the regulator. The recom-
mended value for the filer capacitor is provided in
Section 30.1 “DC Characteristics”.
Tying the ENVREG pin to VSS disables the regulator. In
this case, separate power for the core logic at a nomi-
nal 1.8V must be supplied to the device on the
VDDCORE/VCAP pin.
Alternatively, the VDDCORE/VCAP and VDD pins can be
tied together to operate at a lower nominal voltage.
Refer to Figure 27-1 for possible configurations.
27.4.1 ON-CHIP REGULATOR AND POR
When the voltage regulator is enabled, it takes approxi-
mately 10 μs for it to generate output. During this time,
designated as TSTARTUP, code execution is disabled.
TSTARTUP is applied every time the device resumes
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.
27.4.2 ON-CHIP REGULATOR AND BOR
When the on-chip regulator is enabled,
PIC32MX3XX/4XX 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 Brown-out Reset. This
event is captured by the BOR flag bit (RCON<1>). The
brown-out voltage levels are specific in Section 30.1
“DC Characteristics”.
27.4.3 POWER-UP REQUIREMENTS
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, VDDCORE must
never exceed VDD by 0.3 volts.
FIGURE 27-1:
CONNECTIONS FOR THE
ON-CHIP REGULATOR
Regulator Enabled (ENVREG tied to VDD):
3.3V
PIC32MX
VDD
ENVREG
CEFC
(10 μF typ)
VDDCORE/VCAP
VSS
Regulator Disabled (ENVREG tied to ground):
1.8V⁽¹⁾
3.3V⁽¹⁾
PIC32MX
VDD
ENVREG
VDDCORE/VCAP
VSS
Note 1:
These are typical operating voltages. Refer
to Section 30.1 “DC Characteristics” for
the full operating ranges of VDD and
VDDCORE.
DS61143E-page 576
Preliminary
© 2008 Microchip Technology Inc.