Datasheet

DS_DIM3R3400_08142013 E-mail: [e-mail]
http://www.deltaww.com/dcdc
P9
FEATURES AND DESIGN
CONSIDERATIONS
Introduction
The DIM3R3400 module is designed to simplify the task
and reduce the board space of an ATCA (Advanced
Telecommunications Computing Architecture) power
entry distribution requirements in the system board.
The main functionality of the module is to provide dual,
redundant -48V A/B Feed OR’ing, inrush protection for
hot swap capability, EMI filtering to attenuate the noise
generated by the downstream DC/DC converters, and a
Adjustable Hold Up Voltage from 50 to 95 V for charging
the holdup capacitor. The module also has a
management power supply which provides an 3.3V/3.6A
management power and a 5V/150mA output (optional)
to power the blue LED per PICMG 3.0 requirement.
The module provides A/B feed/fuse open alarm, over
current protection, over voltage protection, and over
temperature protection. It also provides input under
voltage lock-out and input reverse polarity protection.
A/B Feed OR’ing
To improve the total power distribution efficiency, four
internal MOSFETs are used to function as the OR’ing
diodes. A control circuit is designed to keep about 60mV
voltage drop across MOSFET. During full load operation,
the MOSFETs are fully turned on. During light load, the
MOSFETs work under a high Rdson condition. If the
output current decreases to zero, the MOSFETs will be
turned off. This design provides module a reverse
voltage sustain function. The module shall not be
damaged from reverse polarity connection in the event
of mis-wiring of either input feeds at the shelf input
terminals. Furthermore, a fast shut down circuit is
designed for the negative current case. This design
protects the common DC bus against hard short faults at
the sourcing power supply output.
Hot Swap Functionality
The hot-swap function is designed to limit the inrush
current charged to the bulk capacitor of the down stream
bus converter. The current value and duration comply
with the PICMG 3.0’s Inrush Transient specs.
Although the inrush current for bulk capacitor is under
control, special attentions need to be paid to the current
for EMI filter because this circuit is in front of hot-swap
circuit.
EMI Filtering
An internal EMI filter is designed for the ATCA board to
meet the system conducted emission requirements of
CISPR 22 Class B when used with Delta DC/DC
converters.
Figure 11 shows the EMI performance of DIM3R3400
when it worked with Delta power module
Q48SQ12033NRFH. It meets CISPR 22 Class B
requirement.
Figure 11,DIM3R3400 EMI(work with Delta power
module Q48SQ12033NRFH).
Holdup Capacitor Charging
An off line holdup capacitor (C_HLDP) is needed to
store energy for the holdup time requirement. C_HLDP
is charged to a set voltage Vcap(A resistor connect from
Hold up _trim to -48V_out will set the cap voltage). For a
fixed energy storage requirement, high capacitor voltage
reduces capacitor capacitance and size. A constant
current circuit charges C_HLDP before its voltage
reaches the high limitation and isolates it from power
train circuit. The discharge switch will turn on if both
A&B feeds have dropped below –35V (typical). C_HLDP
will be connected to power train and provided the
energy for system operation.
C_HLDP is calculated by the following equation:
VthVthVcapVcap
HLDPTPower
HLDPC
**
_**2
_


Where Power is the input power to the downstream
DC/DC converter and 3.3V input management converter
power; T_HLDP is the holdup time requirement; Vth is
the minimum input voltage threshold of the downstream
DC/DC converter.