dsPIC33CK Low-Voltage Motor Control Board User’s Guide
DS50002927A-page 64 2020 Microchip Technology Inc.
A low forward drop Schottky diode is used for free-wheeling diode D. The average
diode current is calculated using Equation C-5. Based on these calculations, a
MBRA140T3G Schottky diode is selected.
EQUATION C-5:
A standard 1N4148 ultra-fast diode for boost diode D
B was selected based on
recommendations from the “MCP16301/H High-Voltage Input Integrated Switch
Step-Down Regulator Data Sheet” (DS20005004). For more information about the
snubber circuits, R
SNU and CSNU, and series boost resistor, RBOOST, refer to AN1466,
“Reduction of the High-Frequency Switching Noise in the MCP16301 High-Voltage
Buck Converter” (DS01466) application note.
C.3.3 +3.3V Output Power Supply
The second stage of the power supply has the following specifications:
• Input Voltage = +5.0V
• Output Voltage 1 (+3.3V and +3.3 VA) = +3.3V
The MCP1826 LDO is used for generating the +3.3V output. The input of the +3.3V
LDO is the output of the +5V Converter. In the Motor Control Board, digital supply +3.3V
and analog supply +3.3 VA (see Figure C-7) are separated by the jumper resistor R15.
Similarly, Digital Ground (DGND) and Analog Ground (AGND) are separated by the
jumper resistor R19. This is done to logically divide supply lines to analog and digital
circuits during the board layout design.
I
D(AVG)
=
V
BUCK
DC
LOCAL
1 –
I
OUT
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