Product Info

1X UBS Macro B T S FRU P ower Supply Modules (PSMs)
–48 V DC PSM Description
The –48 V DC PSM is a DC–DC converter . It operates from a nominal –48 V DC (–39 to –72 V)
input and provides a 2700 W , +27 V DC (+/– 0.1 V) output. The output is designed to support
load current sharing when configured for parallel output operation with other –48 V DC PSMs.
The PSM has internal fans that circulate cooling air from the front to the rear of the module.
Each –48 V DC PSM slides into a slot in the –48 V DC PSM shelf . Blade type contacts, on the
rear of the –48 V DC PSM, mate with the DC input/output bus bars at the rear of the –48 V
DC PSM shelf .
Each –48 V DC PSM has a rear panel status/alarm drawer connector that mates with a bulkhead
connector in the PSM slot of the PSM shelf . The I/O signals of this connector are interconnected
to the ALARM & CONTROL connector on the front of the –48 V DC PSM shelf . This connector
is cabled to the S SI front panel PSM connector . This allows the PSM alarm & status to be
monitored by the S SI. It also allows the front panel LEDs and module enable to be controlled
by the S SI.
PSM alarm & status signal inputs are current share, temp alarm, converter fail, fan fail, high
temp, low bus voltage, input voltage loss, presence, and EID .
The current share signal goes directly from one PSM to the others via PSM shelf backplane
looping without going to the S SI. Based on PSM alarm & status, the S SI outputs signals to
control the state of the LEDs.
The PSM shelf ALARM & CONTROL cable also contains the PSM enable line which
must be grounded at the S SI in order for the PSM to operate.
68P09283A64 -3 10 -17
FOA SEP 2007