Datasheet

PIC32MX3XX/4XX
DS61143H-page 32 © 2011 Microchip Technology Inc.
FIGURE 2-1: RECOMMENDED
MINIMUM CONNECTION
2.2.1 BULK CAPACITORS
The use of a bulk capacitor is recommended to improve
power supply stability. Typical values range from 4.7 µF
to 47 µF. This capacitor should be located as close to
the device as possible.
2.3 Capacitor on Internal Voltage
Regulator (V
CAP/VCORE)
2.3.1 INTERNAL REGULATOR MODE
A low-ESR (< 1 Ohm) capacitor is required on the
VCAP/VCORE pin, which is used to stabilize the internal
voltage regulator output. The V
CAP/VCORE pin must not
be connected to VDD, and must have a CEFC capacitor,
with at least a 6V rating, connected to ground. The type
can be ceramic or tantalum. Refer to Section 29.0
“Electrical Characteristics” for additional information
on C
EFC specifications. This mode is enabled by
connecting the ENVREG pin to V
DD.
2.3.2 EXTERNAL REGULATOR MODE
In this mode the core voltage is supplied externally
through the V
CORE/VCAP pin. A low-ESR capacitor of
10 µF is recommended on the V
CAP/VCORE pin. This
mode is enabled by grounding the ENVREG pin.
The placement of this capacitor should be close to the
V
CAP/VCORE. It is recommended that the trace length
not exceed one-quarter inch (6 mm). Refer to
Section 26.3 “On-Chip Voltage Regulator” for
details.
2.4 Master Clear (MCLR) Pin
The MCLR pin provides for two specific device
functions:
• Device Reset
• Device Programming and Debugging
Pulling The MCLR
pin low generates a device reset.
Figure 2-2 illustrates a typical MCLR circuit. During
device programming and debugging, the resistance
and capacitance that can be added to the pin must
be considered. Device programmers and debuggers
drive the MCLR
pin. Consequently, specific voltage
levels (V
IH and VIL) and fast signal transitions must
not be adversely affected. Therefore, specific values
of R and C will need to be adjusted based on the
application and PCB requirements.
For example, as illustrated in Figure 2-2, it is
recommended that the capacitor C, be isolated from
the MCLR
pin during programming and debugging
operations.
Place the components shown in Figure 2-2 within
one-quarter inch (6 mm) from the MCLR
pin.
FIGURE 2-2: EXAMPLE OF MCLR PIN
CONNECTIONS
PIC32MX
VDD
VSS
VDD
VSS
VSS
VDD
AVDD AVSS VDD VSS
C
R
V
DD
MCLR
0.1 µF
Ceramic
VCAP/VCORE
10Ω
R1
CBP
0.1 µF
Ceramic
C
BP
0.1 µF
Ceramic
C
BP
0.1 µF
Ceramic
C
BP
0.1 µF
Ceramic
C
BP
CEFC
Note 1: R ≤ 10 kΩ is recommended. A suggested start-
ing value is 10 kΩ. Ensure that the MCLR
pin
V
IH and VIL specifications are met.
2: R1 ≤ 470Ω will limit any current flowing into
MCLR
from the external capacitor C, in the
event of MCLR
pin breakdown, due to
Electrostatic Discharge (ESD) or Electrical
Overstress (EOS). Ensure that the MCLR
pin
V
IH and VIL specifications are met.
3: The capacitor can be sized to prevent uninten-
tional resets from brief glitches or to extend the
device reset period during POR.
C
R1
R
V
DD
MCLR
PIC32MX
JP