Datasheet

DATASHEET
DS_DIM3R3_09102010
10
FEATURES AND DESIGN
CONSIDERATIONS (CONTINUED)
The PICMG 3.0’s requirements for the 0 Vdc transient is
5mS with 50V/ms fall slew rate and 12.5 V/ms rise slew
rate. This requirement will lead to a 9.3ms T_HLDP
requirement assuming power is interrupted at -43Vdc
(Vth).
Considering power output is 300W, Vth is 43V,
)(1672
4372
3.9*300*2
_
22
uFHLDPC 


When the input voltage is at the threshold of discharge,
C_HLDP will go off line and the charge pump will
recharge it to 72V.
The discharge resistor for C_HLDP is not required,
because there is sufficient standby current in the module
to bleed the holdup capacitors from 75V to 60V within 1
second as specified in the PICMG 3.0. Furthermore a
bleed resistor will induce extra loss of the MOSFET of
the charging circuit.
Over-Current Protection
DIM3R3/050 provides two over current protection levels
to protect downstream DC/DC converter over power
rating. When the downstream DC/DC converter over
power rating and caused our output current exceeds the
low current limit level, the current will be kept for a
period of time before the module is shut down. After a
fixed delay time, the module will try to restart. If the
downstream DC/DC converter over power rating and
caused our output current exceeds the high current limit
level, the module will shut down immediately. Then it will
go through the same restarting procedure.
A/B Feed / Fuse Alarm (-48V_ALARM)
The input feeds A and B are monitored. The module will
send an opto-isolated signal if any of the feed is below
the voltage threshold (typical 35V). Therefore, the loss
of any A or B feed can be detected. The opto coupler
transistor on state indicates a normal status and off
state indicates a fault condition.
Input Under Voltage Lockout
The input under-voltage lockout prevents the module from
being damaged by low input voltage. When the input
voltage is lower than its threshold voltage, the module will
be turned off. The lockout occurs between -33.3V to
-35.3V.
Transient Over Voltage Protection
The PICMG 3.0 requires the module work normally
under 200V/5μS and 100V/10μS input voltage transient.
DIM3R3/050 can meet the requirement. An internal TVS
with 80V/1500W peak pulse power rating will suppress
the 200V transient voltage. For the 100V pulse voltage,
the power train impedance will damp it below internal
components rating without shut down the module. When
input voltage of the module is higher than 81.8V, the
module will be turned off. The module will restart when
the input voltage drop down to 79.8V.
Management Power and Blue_LED Power
The module contains two isolated DC output. The first
output provides up to 8W of 3.3V (DIM3R3)
management power (reference to LOGIC_GND). This
power is used to power the IPM controller for the ATCA
board or to power up system controller for other
applications. The second isolated output, 5V/100mA, is
used to power the Blue LED per PICMG 3.0
requirement.
The management power is available as soon as the
input voltage levels are within –36Vdc to –75Vdc. The
output is short circuit and over voltage protected. The
module is in a hiccup mode under an OCP or short
output condition. The output voltage will keep constant
under over voltage status. No additional output
capacitors are required, but a 22µF tantalum/ceramic
and a 0.01µF to 0.1µF ceramic capacitors are highly
recommended to reduce the switching ripple and noise.
Higher output capacitance may be required in case of
large input line or output load transient conditions.