Even if not using USB, the VUSB3V3 must be connected to the VDD in order to power any of the alternate
functions or I/O that share the pins with USBID and VBUSON for those devices that have them.
If using the USB but OTG support is not required, the USBID and VBUSON pin features must be disabled
in the configuration words in order to use any low-priority functions mapped to those pins. When the
USB is enabled these OTG USB extensions USBID and VBUSON become active unless disabled in the
configuration words.
Note: The PIC32MZ devices with USB do not have a VBUSON OTG signal.
10.3 MCLR#/RESETN
Problem 22: MPLAB does not connect to the PIC32 target device.
•
It is critically important that there is a 470-1K isolation resistor separating the PIC32 ICSP MCLR input from the
0.1uf cap and reset supervisor, or reset push button
Figure 10-2. MCLR#/RESETN Circuit Diagram
7
6
5
4
3
1,8,2
MCLR
VDD
VDD
10k
1k
PGDx
PGCx
NC
ICD 4 (MCU RJ45)
PIC32
MX/MM/MZ/MK
Optional
0.1uf
Reset
Supervisor
RESETN
VDDIO
10k
SAM / PIC32C
0.1uf
Optional
Reset
Supervisor
7
6
5
1
ICD 4 (MCU RJ45)
TMS / SWDIO /TMS
TCK / SWTCLK
TDO
3
4
8
TDI
1k
10k(4x)
10.4 VBAT
Problem 23: Do bypass caps need to be used on the VBA
T input pin?
It is recommended to place a 4.7 uf and 0.1 uf capacitor in parallel across the VBAT input pin to ensure that during
the internal switch over from VDD power to VBAT power there are minimal transients as depicted in the diagram
below.
Problem 24: The external battery voltage cannot be measured correctly using the ADC.
When monitoring an external battery, typically users use a voltage divider similar to what is shown below to insure:
• They scale the battery voltage to less than MCU (VDDANA-0.6v) for proper ADC measurements
• That the battery monitoring will draw minimal power from the battery to extend battery life in MCU low power
modes
Due to the large, required resistors used in the battery voltage divider to minimize static power drain from the battery
the sample time required for the ADC to measure the battery is either prohibitive in the application due to other
ADC analog sampling responsibilities in the application, or it is simply not achievable. A simple workaround is to
use a capacitor at the input to the ADC battery input channel. The capacitor will fully charge from 0v in ~ (5 * R1 *
C). When the ADC measures the battery voltage after that period, an infinitesimal small amount of charge from the
external capacitor will instantly be transferred to the ADC internal ~3pF internal hold capacitor that would require only
the minimal sampling ADC time at a reasonable ADC throughput rate. The effective ADC sample/hold RC sampling
time now is simply the ADC internal R
SAMPLE
* C
SAMPLE
. Internal ADC R
SAMPLE
is generally between 2-5k. R1 is a
non-factor now.
PCB MCU Connections
© 2022 Microchip T
echnology Inc.
and its subsidiaries
Manual
DS70005439B-page 31
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