DM330023-2 datasheet(45/64 Pages) MICROCHIP

45 / 64 page

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 VDC/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

1-2

Connects UART receive line to RX.

2-3

Connects USB receive line to RX.

1-2

Connects UART transmit line to TX.

2-3

Connects USB transmit line to TX.

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