Hardware
2009 Microchip Technology Inc.
DS70605A-page 39
4.2.5
Fault Circuitry
In addition to the fault signal generated by the power module, the system can also
create a DC bus overcurrent fault.
DC Bus Overcurrent,
this fault signal is generated when the maximum current limit of
15A is reached. The comparison of the threshold value and the actual current is done
by comparator U14. The threshold limit is set by R42 and R47. R69 is a shunt jumper
resistor that can disconnect the overcurrent fault from the dsPIC DSC.
4.2.6
Isolation
The power supply used by the push buttons, communication ports, and the SKDE pro-
grammer/debugger is isolated from the power supply used by the power module or the
dsPIC DSC. An isolated 3.3V rail is generated from the digital 3.3V rail using a
DC-to-DC converter (U10). This converter provides galvanic isolation rated up to
1000 V
DC
/1 second.
4.2.7
Communication Ports
The power module stage board provides two methods for transmitting/receiving data to
and from the system. Both communication methods are powered using the isolated
3.3V rail.
UART-to-USB
communication port is based on a PIC18LFJ2450 device with a serial
emulator firmware. This device translates the USB signals to dsPIC DSC UART com-
patible signals. The firmware used for this serial emulator is enclosed in the CD shipped
along with the unit. Isolation for the UART-to-USB communication port is provided by
U25.
UART-to-RS-232
communication port is based on a RS-232 transceiver (U9). This
device translates the dsPIC DSC UART signals to UART compatible signals. Isolation
for the UART-to-RS-232 communication port is provided by U25.
Shunt jumpers J2 and J3 select the communication port. Table 4-5 shows the possible
configurations.
TABLE 4-5:
COMMUNICATION PORT CONFIGURATION
Note:
The comparator is open-drained and needs an external pull-up resistor.
Both the power module output and the comparator output share this pull-up
resistor creating an OR condition at the output.
Designator
Position
Description
J2
1-2
Connects UART receive line to RX.
2-3
Connects USB receive line to RX.
J3
1-2
Connects UART transmit line to TX.
2-3
Connects USB transmit line to TX.
