rtd ATX104HR-EXPRESS, User Manual

Page: 17 / 43

ATX104HR-EXPRESS
User’s Manual
ATX104HR-EXPRESS 17 RTD Embedded Technologies, Inc.
Main +5V and +3.3V converter for the computer
The main +5V and the PCI bus +3.3V output use a synchronous, switch-mode DC-
DC converter design. The output current of both of these independent converters
this limited to 10A. These converters have excellent dynamic and transient
response capabilities making it an ideal high-speed computer power supply. Use
of low loss MOSFET-transistors allows operation without an additional heat-sink.
Internal layers of the PCB are used to distribute heat evenly.
Input circuitry of the ATX104HR-EXPRESS is protected with a 36V fast transient
absorber diode and a low loss forward schottky diode. These devices are
necessary to protect the input in automotive and industrial installations against fast
over-voltage spikes and reverse voltage transients. These situations exist in
vehicle systems with alternators/chargers or in systems with electrically controlled
hydraulic or pneumatic inductive valves and solenoids.
The +5V converter, located closer to the power connectors, feeds the PC/104 AT
bus and the PCI bus +5V pins with power. This power can also be supplied from
the board from an external terminal block TB2. (See previous section for the
location of terminal block TB2.) The +3.3V converter located near the PCI bus
connector only feeds the +3.3V power pins of the PCI bus. A terminal block at the
side of the board next to the +5V output can be used to power other external
+3.3V devices.
Input range is guaranteed from 8 up to 36V under full load and in worst conditions
over the full rated temperature range (with air flow). Note that start up current may
exceed stead-state current consumption.
Current Limit
To protect against fault or short-circuit conditions 5V and 3.3V voltages are
equipped with current fold-back, current limiting circuitry to provide continuous
overload protection. After reaching the current limit point the voltage output will
range between the rated output voltage and zero depending on the amount of
overload Once the short circuit condition is removed, the output will return to the
nominal value without restarting the unit.
Remote On/Off control
X1 controls the 5Vstby and X2 controls all other voltages. See the table in the
“Connector
Descriptions:
” labeled “X1-X2 operations”. Complete power off is achieved when X1 =1-2 and X2
= open.