Thales NSS 100S-1 Component Maintenance Manual With Illustrated Parts List page 71

(5) Amplitude limiter circuit
This circuit monitors the +28VFILT input voltage; it commands Q2 whenever
the voltage is higher than + 35 V; Q2 absorbs the excess energy, thereby
enabling PCB Z1 to withstand a transient surge of 60 V for 100 ms (pulse
state).
(6) Energy reserve switching
This circuit is connected to two capacitors C2 and C3 (a total of 2000
µF), connected to the DC/DC terminal by transistor CMOS Q3.
Whenever operation is normal, (steady state), both capacitors are char-
ged by the +28VFILT.
Whenever the +28VFILT is less than +17 V, the "Reserve order" signal,
generated by the protection circuit is applied to the switching circuit;
the switching circuit commands Q3 which becomes conductor.
Converter PS3 is now powered by both capacitors during power transients
of less than 1 ms.
(7) Battery management circuit
This circuit is designed to generate a backup voltage (+5VSPIL), which
replaces +5VUC once it disappears. It also delivers a monitoring signal
(SURPILE), which is indicative of battery condition which is processed
by the central processing unit.
The battery management circuit is connected to the two 3.5 V batteries,
BT1 and BT2 mounted on PCB Z1.
The back-up voltage generated is adjusted and calibrated to + 5V ± 0.5 V
(8) Generation of MST and ITCOUPAL signals
These two signals are generated from +5VUC voltages, -15VUC and using
the "Reserve command" signal (created earlier) after matching by an
optical electrical coupler.
The MST initialization signal is generated when the power is switched
on, 100 ms after the +28VFILT appears.
The ITCOUPAL signal (power supply cut-off interrupt) is generated for
cut-offs > 1 ms.
© THALES AVIONICS
COPYRIGHT SEXTANT Avionique 1995
c
The document reference is online, please check the correspondence between the online documentation and the printed version.
COMPONENT MAINTENANCE MANUAL
C17004
34-57-96
Page 45
OCT 15/01