Newport New Focus 8703, Руководство пользователя

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Theory of Operation 13
Status Indicators position
The red LED is tied to LFAULT (pin 15). It will flash the firmware revision
number when the unit is turning on, and will also turn on if the output
amplifier temperature approaches the design limit.(You can also monitor the
temperature using the TEMP MONITOR, pin 21. This pin has a 100 k
Ω
output impedance. The relationship between TEMP MON voltage and
output-amplifier temperature is shown in Figure 4.)
The green LED monitors drive pulses. The LED is turned off each time a
Picomotor drive pulse is generated. As the pulse frequency is increased, the
LED is off a greater fraction of time. This dimming effect is used to visually
ensure correct operation.
3.4 Power Supply
The 8712 module can place tremendous stress on the system power supply.
The stress has two components:
•
Inrush current: The inrush current on power-up charges the internal
filter capacitor. While the energy magnitude of the inrush current is
limited, it can still cause problems with power supplies not designed to
handle it.
•
Dynamic load: Dynamic current is supplied to the 8712 internal power
supply for each Picomotor drive pulse. The input-filter capacitor will
supply more dynamic current as the resistance between the capacitor and
system power supply increases. Do not increase this resistance: it will
increase ripple-current stress on the internal input-filter capacitor,
leading to early failure of the 8712 module. The best strategy is to keep
the resistance between the power supply and the 8712 below 0.1
Ω
and
specify a system power supply that can handle the dynamic current
requirement.
3.4.1 Fault Protection
The 8712 incorporates circuit-protection schemes to protect itself and the
system power supply:
Green and
red LEDs
can be seen
through
these holes.