Product # SQ60120QPB33 Phone 1-888-567-9596 www.synqor.com Doc.# 005-0005266 Rev. F 03/29/11 Page 10
Technical
Specification
SQ60120QPB33
Application Section
Application Section
BASIC OPERATION AND FEATURES
With voltages dropping and currents rising, the economics
of an Intermediate Bus Architecture (IBA) are becoming
more attractive, especially in systems requiring multiple
low voltages. IBA systems separate the role of isolation and
voltage scaling from regulation and sensing. The BusQor
series bus converter provides isolation and a coarse voltage
step down in one compact module, leaving regulation to
simpler, less expensive non-isolated converters.
In Figure A below, the BusQor module provides the isolation
stage of the IBA system. The isolated bus then distributes
power to the non-isolated buck regulators to generate the
required voltage levels at the point of load. In this case, the
bucks are represented with SynQor’s NiQor series of non-
isolated dc-dc converters. In many applications requiring
multiple low voltage outputs, signicant savings can be
achieved in board space and overall system costs.
When designing an IBA system with bus converters, the
designer can select from a variety of bus voltages. While
there is no universally ideal bus voltage, most designs
employ one of the following: 12V, 9V, 7.5V, 5V, or 3.3V.
Higher bus voltages can lead to lower efciency for the buck
regulators but are more efcient for the bus converter and
provide lower board level distribution current. Lower bus
voltages offer the opposite trade offs.
SynQor’s SQ BusQor modules accept the full 48/60V
telecom bus voltage and have a narrow output voltage
range compatible with many non-isolated point of load
converters. When used in IBA systems, the output variation
of the BusQor must be in accordance with the input voltage
range of the non-isolated converters being employed.
BusQor
Converter
NiQor
Converters Loads
48Vdc
Front End
Typical User Board
3.3V
CONTROL FEATURES
REMOTE ON/OFF (Pin 2): The ON/OFF input, Pin 2,
permits the user to control when the converter is on or off.
This input is referenced to the return terminal of the input
bus, Vin(-). There are two versions of the converter that
differ by the sense of the logic used for the ON/OFF input.
In the positive logic version, the ON/OFF input is active
high (meaning that a high turns the converter on). In the
negative logic version, the ON/OFF signal is active low
(meaning that a low turns the converter on). Figure B is a
detailed look of the internal ON/OFF circuitry.
TTL
ON/OFF
Vin(_)
Vin(
+
)
2.5V
1.8V
1.5V
0.9V
12Vdc
48Vdc
36-75V
Figure A: Example of Intermediate Bus Architecture using BusQor bus converter
and NiQor non-isolated converters
5V
+5V
124k
49.9k
100k
Figure B: Internal ON/OFF pin circuitry
Protection Features
Input Under-Voltage Lockout: The converter is designed
to turn off when the input voltage is too low, helping avoid
an input system instability problem, described in more detail
in the application note titled “Input System Instability”
available on www.SynQor.com. The lockout circuitry is a
comparator with DC hysteresis. When the input voltage is
rising, it must exceed the typical Turn-On Voltage Threshold
value (listed on the specication page) before the converter
will turn on. Once the converter is on, the input voltage
must fall below the typical Turn-Off Voltage Threshold value
before the converter will turn off. Also see Fig E.
Output Current Limit: The output of the BusQor module
is electronically protected against output overloads. When
an overload current greater than the “DC Current-Limit
Inception” specication is drawn from the output, the
output of the BusQor will shutdown to zero volts after the
1ms have elapsed (see Fig C). The shutdown period lasts
for a typical period of 200ms (Fig D) after which the BusQor
tries to power up again. If the overload persists, the output
voltage will go through repeated cycles of shutdown and
restart with a duty cycle of 20ms (On) and 200ms (Off)
respectively. The BusQor module returns (auto resetting)
to normal operation once the overload is removed. The
BusQor is designed to survive in this mode indenitely
without damage and without human intervention.
Output
Current
Output
Voltage
<12V
0V Time
Peak
55A
peak
5V
+5V
124k
49.9k
100k
Output Short Circuit Protection: When the output of
the BusQor module is shorted, a peak current of typically 55A
will ow into the short circuit for a time of about 1ms. The
output of the BusQor will shutdown to zero volts after the
1ms have elapsed (Fig C & D). The shutdown period lasts
for a time of 200ms, at the end of which the BusQor module
tries to power up again. If the short circuit persists, the
output voltage will go through repeated cycles of shutdown
and restart with a duty cycle of 20ms (On) and 200ms (Off)
respectively. The BusQor module returns (auto resetting)
to normal operation once the short circuit is removed. The
BusQor is designed to survive in this mode indenitely
without damage and without human intervention.
In the Auto resetting mode, also referred to as “Hiccup”
mode, the power drawn from the 48V input is about 5W,
most of which is dissipated into the external fault. It is
important that copper traces and pads from the output
circuit be designed to withstand the short term peaks,
although the average current into the fault may be as low
as 50mA typical. See Fig 17 for appropriate waveform.
Over-Temperature Shutdown: A temperature sensor
on the converter senses the average temperature of the
module. The thermal shutdown circuit is designed to turn
the converter off when the temperature at the sensed
location reaches the Over-Temperature Shutdown value.
It will allow the converter to turn on again when the
temperature of the sensed location falls by the amount of
the Over-Temperature Shutdown Restart Hysteresis value.
Output
Current
Output
Voltage
0V
Time
55A
33A
12V
1ms
Figure C: Output Overload protection diagram (not to scale)
<12V
200ms 20ms
Figure D: Output Short Circuit and Auto-Resetting protection diagram (not to scale)