Front Panel Assembly - Agilent Technologies 16800 Series Service Manual

8
Theory of Operation

Front Panel Assembly

176
Fan Control The instrument uses a pair of 24 V fans driven
from a DC/DC boost converter circuit. This circuit creates a
linear voltage ramp from 12 V to 24 V across the operating
temperature range. The purpose of this circuit is to increase
air flow as needed while maintaining the lowest possible fan
noise.
The identical front panel assembly with LCD is used on all
16800 Series logic analyzers. The front panel assembly is
composed of two PC boards comprising three independently
operating sub- systems. The two PC boards are the front
panel interface board and the keypad board. The three front
panel sub- systems are:
• Front panel keypad board.
• Front panel interface board.
• Front panel touch screen (Option 103).
Front Panel Keypad Board
The front panel switches consist of five buttons and one
digital encoder, the knob. When a button is pressed and
released, or the knob turned, a series of codes are sent back
to the module FPGA. When the module FPGA receives a
front panel code, an interrupt is sent to the system CPU.
The resulting ISR will read the code and act on it.
The module FPGA was used as a convenient place to put
this logic. This logic operates independently of the module
backplane logic also within the module FPGA.
Front Panel Interface Board
The front panel interface board plugs into the CPU
motherboard's PCI Express x16 slot and provides a
connection point for flat- panel display communication.
The connectors J2 and J3 are connected to a Mitsubishi 15"
AA150XN01
XGA TFT- LCD 1024x768 display:
• Connector J2 provides the data path back to an Adlink
video adapter.
• Connector J3 is used to provide the high- voltage needed
to light the display backlight. This high- voltage is
generated using a power inverter board, which is mounted
on the front panel interface board. This power inverter
board is a TDK CXA- 0384 DC- AC Inverter Unit.
16800 Series Portable Logic Analyzers Service Guide