PIC32MX320F032H_11 Datasheet, PDF (138/214 Pages) Microchip Technology – High-Performance, General Purpose and USB, 32-bit Flash Microcontrollers

PIC32MX3XX/4XX
26.3 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 VCORE/VCAP pin (Figure 26-2). This helps to
maintain the stability of the regulator. The recom-
mended value for the filer capacitor is provided in
Section 29.1 “DC Characteristics”.
Note:
It is important that the low ESR capacitor
is placed as close as possible to the
VCORE/VCAP pin.
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
VCORE/VCAP pin.
Alternatively, the VCORE/VCAP and VDD pins can be tied
together to operate at a lower nominal voltage. Refer to
Figure 26-2 for possible configurations.
26.3.1 ON-CHIP REGULATOR AND POR
When the voltage regulator is enabled, it takes fixed
delay for it to generate output. During this time, desig-
nated as TPU, code execution is disabled. TPU 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 TPWRT at device start-up. See
Section 29.0 “Electrical Characteristics” for more
information on TPU AND TPWRT.
26.3.2 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 29.1
“DC Characteristics”.
26.3.3 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, VCORE must never
exceed VDD by 0.3 volts.
FIGURE 26-2:
CONNECTIONS FOR THE ON-CHIP REGULATOR
Regulator Enabled (ENVREG tied to VDD):
3.3V
PIC32MX
VDD
ENVREG
CEFC
(10 μF typ)
VCORE/VCAP
VSS
Regulator Disabled (ENVREG tied to ground):
1.8V⁽¹⁾
3.3V⁽¹⁾
PIC32MX
VDD
ENVREG
VCORE/VCAP
VSS
Note 1: These are typical operating voltages. Refer to Section 29.1 “DC Characteristics” for the full operating ranges of VDD
and VCORE.
DS61143H-page 138
© 2011 Microchip Technology Inc.