PTB48520W Datasheet, PDF (6/18 Pages) Texas Instruments – 25-A, 48-V INPUT ISOLATED DC/DC CONVERTER WITH AUTO-TRACK™ SEQUENCING

PTB48520W
SLTS233A – NOVEMBER 2004 – REVISED APRIL 2005
TYPICAL CHARACTERISTICS (continued)
Safe Operating Areas; V_I = 48 V⁽²⁾
www.ti.com
TEMPERATURE DERATING
vs
OUTPUT CURRENT (V_O Bus)
90
TEMPERATURE DERATING
vs
OUTPUT CURRENT (V_O Seq)
90
80
70
400 LFM
60
200 LFM
50
100 LFM
40
Nat Conv
80
100 LFM
Nat Conv
70
60
50
40
30
Airflow
20
0
5
10
15
20 25
I_O − Output Current − A
30
Airflow
20
0
2
4
6
8
10
I_O − Output Current − A
Figure 4.
Figure 5.
(2) The temperature derating curves represent operating conditions at which internal components are at or below manufacturer's maximum
rated operating temperature. See Figure 4 and Figure 5.
APPLICATION INFORMATION
Operating Features and System Considerations for the PTB48520W DC/DC Converter
Overcurrent Protection
To protect against load faults, these converters incorporate output overcurrent protection. Applying a load to the
output that exceeds the converter overcurrent threshold (see applicable specification) causes the output voltage
to momentarily fold back, and then shut down. Following shutdown, the module periodically attempts to
automatically recover by initiating a soft-start power up. This is often described as a hiccup mode of operation,
whereby the module continues in the cycle of successive shutdown and power up until the load fault is removed.
Once the fault is removed, the converter automatically recovers and returns to normal operation.
Output Overvoltage Protection
The converter continually monitors for an output overvoltage (OV) condition, directly across the +V_O Bus output.
The OV threshold automatically tracks the output voltage set point to a level that is 25% higher than that set by
the external R_(SET) voltage adjust resistor. If the output voltage exceeds this threshold, the converter is
immediately shut down and remains in a latched-off state. To resume normal operation, the converter must be
actively reset. This can only be done by momentarily removing the input power to the converter. For fail-safe
operation and redundancy, the OV protection uses circuitry that is independent of the converter internal feedback
loop.
Differential Output Voltage Sense
A differential remote sense allows a converter regulation circuitry to compensate for limited amounts of IR drop,
that may be incurred between the converter and load, in either the positive or return PCB traces. Connecting the
(+)Sense and (–)Sense pins to the respective positive and ground reference of the load terminals improves the
load regulation of the converter output voltage at that connection point. The (–)Sense pin should always be
connected to the V_O COM. The (+)Sense pin may be connected to either the +V_O Bus or +V_O Seq outputs.
When the (+)Sense pin is connected to the V_O Seq output, the voltage at V_O Bus voltage regulates slightly
6