bq50120qta20pysbq55090qta27pyc SynQor Worldwide Headquarters, bq50120qta20pysbq55090qta27pyc Datasheet - Page 8

• Manufacturer Part Number: bq50120qta20pysbq55090qta27pyc
• Description: Quarter-brick Dc Busconverter
• Manufacturer: SynQor Worldwide Headquarters

Product # BQ50120QTA20
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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 volt-
age levels at the point of load. In this case, the bucks are rep-
resented with SynQor’s NiQor series of non-isolated dc/dc con-
verters. In many applications requiring multiple low voltage out-
puts, significant 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 uni-
versally ideal bus voltage, most designs employ one of the fol-
lowing: 12V, 9V, 7.5V, 5V, or 3.3V. Higher bus voltages can
lead to lower efficiency for the buck regulators but are more effi-
cient for the bus converter and provide lower board level distrib-
ution current. Lower bus voltages offer the opposite trade offs.
SynQor’s 12Vout BusQor module acts as a true dc transformer.
The output voltage is proportional to the input voltage, with a
specified “turns ratio” or voltage ratio, plus minor drop from the
internal resistive losses in the module. When used in IBA sys-
tems, the output variation of the BusQor must be in accordance
Figure A: Example of Intermediate Bus Architecture using
BusQor bus converter and NiQor non-isolated converters
echnical S
echnical S
42-53V
48Vdc
48Vdc
Front
End
Typical User Board
Converter
BusQor
pecification
pecification
12Vdc
Phone [phone]
Converters
NiQor
3.3 V
0.9 V
2.5 V
1.8 V
1.5 V
Loads
www.synqor.com
with the input voltage range of the non-isolated converters being
employed.
The BusQor architecture is very scalable, meaning multiple bus
converters can be connected directly in parallel to allow current
sharing for higher power applications.
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. Positive logic enabled modules have
N-channel FET populated. Negative logic enabled modules have
P-channel FET populated.
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 appli-
cation note titled “Input System Instability” available on the
SynQor website. 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 specifica-
tion 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 Figure E.
Figure B: Internal ON/OFF pin circuitry
N-channel FET
Doc.# 005-2BQ512J Rev. E
Control
P-channel FET
P
P
Current:
Current:
ackage:
ackage:
Output:
Output:
Input:
Input:
13V
03/17/06
5 k
42-53 V
12 V
20 A
Quarter-brick
42-53 V
12 V
20 A
Quarter-brick
Ω
Vref
100 k
(8V)
30 k
Ω
Ω
On/Off
Vin+
Vin-
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