2070LX Controller – User Manual 55
Version 1.0
Voltage monitors
In order to monitor the voltage levels for +5VDC, +12VDC and -12VDC voltage dividers are arranged and
connected to the microcontroller’s ADC’s, if the monitored levels are within range the LED status
indicators are activated.
Voltage status indicators
A LED status indicator for each power supply is provided to indicate if the voltage levels are within range
or not; The LED status indicator is ON if the voltage supply is within range and OFF otherwise: the +5
VDC is within 5% and the 12 VDC is within 8% of their nominal levels.
The LED DC POWER Indicator indicates that the required DC Voltage meets the following conditions: For
the +5VDC, +12VDC and -12VDC supplies, the circuit consists of an LED in series with a 220 Ohms
resistor, connected to +3.3VDC and activated by the microcontroller.
For the +12VDCISO supply, a discrete voltage monitor device is used. It monitors and indicates if the
level is within range. In this case there is an LED with a 2.2KOhms series resistor connected to
+12VDCISO and activated by this device.
Standby Power
+ 5 VDC STANDBY POWER is provided to hold up system devices during power down period. It consists
of the monitor circuitry; hold up capacitors, and charging circuitry. A charging circuit is provided that under
normal operation fully charges and float the capacitors. The Hold Up power requirements are a minimum
constant drain of 600uA at a range of +5 to +2 VDC for over 10 hours.
It is achieved through the high efficiency positive voltage regulator ICL7663 and two 47F hold up
capacitors plus charging circuitry.
Holdup time
The Power Supply module is able to deliver at least 30W for 550ms after the ACFAIL line is set to Low. It
is capable of holding the unit for two 500ms power failure periods occurring in a 1.5 seconds period.
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