1 5 W , D U A L O U T P U T , M I X E D - V O L T A G E D C / D C C O N V E R T E R S
XWR Series
for D48 models). Once operating, devices will not turn off until the input
voltage drops below the Undervoltage Shutdown limit (34V for D48 models).
Subsequent re-start will not occur until the input is brought back up to
the Start-Up Threshold. This built in hysteresis prevents any unstable on/off
situations from occurring at a single input voltage.
Absolute Maximum Ratings
Input Voltage:
Continuous:
D12 Models
D24 Models
D48 Models
21 Volts
40 Volts
81 Volts
25 Volts
50 Volts
100 Volts
Transient (100msec): D12 Models
D24 Models
D48 Models
Input voltages exceeding the input overvoltage shutdown specification listed
in the Performance/Functional Specifications will cause the device to shut-
Input Reverse-Polarity Protection: ➁ Input Current must be limited. 1 minute
duration. Fusing recommended.
down. A built-in hysteresis of 0.6 to 1.6 Volts for all models will not allow the
converter to restart until the input voltage is sufficiently reduced.
D12 Models
D24 Models
D48 Models
3 Amps
2 Amps
1 Amps
Start-Up Time
Output Current ➁
Current limited. Devices can withstand
an indefinite output short circuit.
The VIN to VOUT start-up time is the interval of time where the input voltage
crosses the turn-on threshold point, and the fully loaded output voltage enters
and remains within its specified accuracy band. Actual measured times will
vary with input source impedance, external input/output capacitance, and the
slew rate of the input voltages. The XWR 15 Watt Series implements a soft
start circuit that limits the duty cycle of the PWM controller at power up,
thereby limiting the Input Inrush current.
On/Off Control (Pin 3) Max. Voltages:
Referenced to –Input (pin 2)
+VIN
Storage Temperature
–40 to +120°C
Lead Temperature (Soldering, 10 sec.) +300°C
These are stress ratings. Exposure of devices to any of these conditions may adversely
affect long-term reliability. Proper operation under conditions other than those listed in the
Performance/Functional Specifications Table is not implied, nor recommended.
The On/Off Control to VOUT start-up time assumes the converter has its
nominal input voltage applied but is turned off via the On/Off Control pin.
The specification defines the interval between the time at which the converter
is turned on and the fully loaded output voltage enters and remains within
its specified accuracy band. Similar to the VIN to VOUT start-up, the On/Off
Control to VOUT start-up time is also governed by the internal soft start
circuitry and external load capacitance.
T E C H N I C A L N O T E S
Isolation / Case Connection
On/Off Control
The XWR Series’ 5V and 3.3V outputs (pins 5 & 8) with its common return
(pin 7) are isolated from the +VIN and –VIN inputs (pins 1 & 2) via a
transformer and an opto-coupled transistor.
The On/Off Control (pin 3) may be used for remote on/off operation. As
shown in Figure 1, the control pin is referenced to the –Input (pin 2) and will
be internally pulled to a high state. The XWR Series is designed so that it is
enabled when the control pin is left open (pulled high) and disabled when the
control pin is pulled low (less than +0.8V relative to –Input).
The DC/DC converter’s case is internally connected to pin 4. This allows
circuit specific grounding of the case on either the input or the output side, or
leaving the case disconnected, i.e. “floating.”
Dynamic control of the on/off function is best accomplished with a mechanical
relay or an open-collector/open-drain circuit (optically isolated if appropriate).
The drive circuit should be able to sink approximately 1 mA for logic low.
Input Fusing
Certain applications and/or safety agencies may require the installation of
fuses at the inputs of power conversion components. Fuses should also be
used if the possibility of a sustained, non-current-limited, input-voltage polar-
ity reversal exists. For XWR 15 Watt Series Converters, it is recommended
to install slow blow fuses with values no greater than the following, in the
+Input line.
The on/off control function is designed such that the converter can be
disabled while the input power is ramping up, and then “released” once the
input has stabilized.
VIN Range
D12 Models
D24 Models
D48 Models
Fuse Value
3 Amps
+INPUT
1
3
2 Amps
13V CIRCUIT
5V CIRCUIT
1 Amps
ON/OFF
CONTROL
Input Reverse-Polarity Protection
Upon applying a reverse-polarity voltage to the DC/DC converter, an internal
diode will be forward biased, drawing excessive current from the power
source. Therefore, it is required that the input current be limited by either an
appropriately rated input fuse or a current limited power source.
–INPUT
2
Input Overvoltage/Undervoltage Shutdown and Start-Up Threshold
Figure 1. Internal On/Off Control circuitry
Under normal start-up conditions, devices will not begin to regulate until
the ramping-up input voltage exceeds the Start-Up Threshold Voltage (35V
4
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