When Power Is Lost - HP M2350A Service Manual

Understanding the Computer Module
The DC/DC Converter
60V
+12v
-12v
Figure 2-3. DC/DC Converter Block Diagram
When the system is switched on, 60V appears at the input 15-pin power-in connector of the
converter. There is a delay of between one to two seconds to ensure that both SYRES and
PFAIL are in the correct state Then the regulated voltages from the DC/DC converter's SMPS
are output onto the utility bus on the backplane of the computer module. The voltages output
are:
+12v
-12v
+5v
The 60V input is also placed on the utility bus via the DC/DC Converter input connector.
When Power is Lost
When power is lost, the DC\DC converter asserts a PFAIL signal on the MPB to alert all the
cards that power will be lost. After a brief delay, the Utility CPU places a SYRES signal on the
MPB. After another brief delay, SYRES is deasserted, allowing the system to reset all the cards
simultaneously.
2.8