BWR-5/6-3.3/7-D12 데이터 시트보기 (PDF) - DATEL Data Acquisition products
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BWR-5/6-3.3/7-D12
DATEL Data Acquisition products
BWR-5/6-3.3/7-D12 Datasheet PDF : 11 Pages
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33W, DUAL OUTPUT, MIXED-VOLTAGE DC/DC CONVERTERS
BWR Models
Sync Function (Optional)
In critical applications employing multiple switching DC/DC converters, it
may be necessary to synchronize the switching of selected converters.
These BWR converters offer an optional Sync function ("S" suffix) in place
of the On/Off Control on pin 4. The Sync pin will self configure as either
a slave or master, depending on the application. If the Sync pin detects
the appropriate input signal it will configure itself as a slave, if no signal is
detected it will generate master Sync pulses.
Synchronization of converters requires that the master switching frequency
exceed the slave frequency by a minimum of 60kHz. At the start of each
DC/DC converter switching cycle, an internally generated 160-360ns pulse
will be present at the Sync pin. If, however, the unit receives an external
Sync pulse, the DC/DC converter’s switching cycle will be reset, and a new
cycle initiated. Since the master frequency is higher than the slave’s switching
frequency, the slave cycles are always terminated prematurely, thereby never
allowing internal Synch pulses to be generated. The external signal’s rising
edge initiates the slave Sync process. External signals must adhere to min./
max. limits stated in Performance/Functional Specifications.
Operating these BWR converters at higher switching frequencies via the
external Sync function will result in a slight degradation of efficiency.
Contact the DATEL for further information.
Current Limiting
When power demands from either output fall within 126% to 181% of the rated
output current, the DC/DC converter will go into a current limiting mode. In
this condition both output voltages will decrease proportionately with increases
in output current, thereby maintaining a somewhat constant power dissipa-
tion. This is commonly referred to as power limiting (see Figures 2a and
2b). Current limit inception is defined as the point where the full-power output
voltage falls below the specified tolerance. If the load current being drawn
from the converter is significant enough, the unit will go into a short circuit
condition. See "Short Circuit Condition."
Typical Current Limiting Characteristics for 3.3V Output
4
3
2
VIN NOM, VIN LO All Models
1
VIN HI D12, D24 Models
VIN HI
D48 Models
0
0
2
4
6
8
10
12
14
3.3 VOUT Average Ouput Current (Amps)
Figure 2a. Current Limiting Characteristics for 3.3V Output
Typical Current Limiting Characteristics for 5V Output
(3.3V Output @ 700mA)
5
4.5
4
3.5
3
2.5
2
VIN NOM, VIN LO
1.5
All Models
VIN HI D12, D24
1
Models
VIN HI
0.5
D48 Models
0
0
1
2
3
4
5
6
7
8
9
5 VOUT Average Ouput Current (Amps)
Figure 2b. Current Limiting Characteristics for 5V Output
Short Circuit Condition
When a converter is in current limit mode the output voltages will drop as the
output current demand increases (see figures 2a and 2b). If the output volt-
age drops too low, the magnetically coupled voltage used to develop primary
side voltages will also drop, thereby shutting down the PWM controller.
Following a time-out period of 5 to 15 milliseconds, the PWM will restart,
causing the output voltages to begin ramping to their appropriate values. If
the short-circuit condition persists, another shutdown cycle will be initiated.
This on/off cycling is referred to as "hiccup" mode. The hiccup cycling
reduces the average output current, thereby preventing internal temperatures
from rising to excessive levels. The BWR is capable of enduring an indefinite
short circuit output condition.
Thermal Shutdown
These BWR converters are equipped with Thermal Shutdown Circuitry. If
the internal temperature of the DC/DC converter rises above the designed
operating temperature, a precision temperature sensor will power down the
unit. When the internal temperature decreases below the threshold of the
temperature sensor the unit will self start.
Output Overvoltage Protection
Both output voltages are monitored for an overvoltage condition via magnetic
coupling to the primary side. If either output voltage should rise to a level
which could be damaging to the load circuitry, the sensing circuitry will power
down the PWM controller causing the output voltages to decrease. Following
a time-out of 5 to 15 milliseconds the PWM will restart, causing the output
voltages to ramp to their appropriate values. If the fault condition persists,
and the output voltages again climb to excessive levels, the overvoltage
circuitry will initiate another shutdown cycle. This on/off cycling is referred
to as "hiccup" mode.
5
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