TWR Series
30W, Triple Output DC/DC Converters
Start-Up Threshold and Undervoltage Shutdown
Absolute Maximum Ratings
Input Voltage:
Continuous:
Under normal start-up conditions, TWR 30W triples will not begin to regulate
until the ramping input voltage exceeds the Start-Up Threshold Voltage
(typically 17V for "D24" models and 35V for "D48" models). Once operating,
devices will not turn off until the input voltage drops below the Undervoltage
Shutdown/Lockout limit (typically 16.5V for "D24" models and 34.5V 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 obviously avoids any
indeterminate on/off conditions at a single voltage.
D24A Models
D48A Models
42 Volts
81 Volts
50 Volts
100 Volts
Transient (100msec): D24A Models
D48A Models
Input Reverse-Polarity Protection ꢂ
Input Current must be limited. 1 minute
duration. Fusing recommended.
D24A Models
D48A Models
4 Amps
2 Amps
Output Current ꢂ
Current limited. Devices can withstand
an indefinite output short circuit.
Start-Up Time
On/Off Control (Pins 3 & 4) Max. Voltages
Referenced to –Input (pin 2)
No Suffix
For all models in the TWR 30W Series, VIN to VOUT Start-Up Time is the
interval between the time at which a rapidly ramping input voltage crosses
the turn-on threshold point and the fully loaded output voltages enter and
remain within their specified accuracy bands. Actual measured times will vary
with output capacitance and load.
+VIN
+5.7 Volts
"S" Suffix
Storage Temperature
Lead Temperature
–40 to +120°C
See soldering guidelines
The On/Off to VOUT Start-Up Time assumes the converter is turned off via
the On/Off Control with the nominal input voltage already applied to the con-
verter. The specification defines the interval between the time at which the
converter is turned on and the fully loaded output voltages enter and remain
within their specified accuracy bands.
These are stress ratings. Exposure of devices to greater than 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.
TECHNICAL NOTES
On/Off Control
I/O Filtering and Noise Reduction
The On/Off Control pin (pin 4) is provided for remote on/off operation.
TWR 30W Series converters are designed so that they are enabled when the
control pin is pulled high or left open (normal mode) and disabled when the
control pin is pulled low (to less than +0.8V relative to –Input, pin 2).
All TWR 30W Series models achieve their rated ripple and noise specifica-
tions without the use of external input/output capacitors. In critical applica-
tions, input/output ripple/noise may be further reduced by installing additional
external I/O caps. Input capacitors, which function primarily as energy-
storage elements, should be selected for bulk capacitance, low ESR and
high rms-ripple-current ratings. Output capacitors, which function more as
true filter elements, should be selected for bulk capacitance, low ESR, and
appropriate frequency response. All caps should have appropriate voltage
ratings and be mounted as close to the converters as possible. Temperature
variations for all parameters should obviously be taken into consideration.
Dynamic control of the on/off function is best accomplished with a mechani-
cal relay or an open-collector/open-drain drive circuit (optically isolated if
appropriate). The drive circuit should be able to sink appropriate current (see
Performance/Functional Specifications) when activated..
Applying an external voltage to pin 4 when no input power is applied to the
converter can cause permanent damage to the converter. The on/off control
function, however, is designed such that the converter can be disabled (pin
4 pulled low) while input power is ramping up and then "released" once the
input has stabilized. The time duration between the point at which the con-
verter is released and its fully loaded output voltage settles to within specified
accuracy can be found in the Performance/Functional Specifications.
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 sustained, non-current-limited, input-voltage polarity
reversals exists. For DATEL TWR 30W DC/DC Converters, you should use
slow-blow type fuses with values no greater than the following.
Model Number
Fuse Value
TWR-3.3/4250-12/625-D24
TWR-3.3/4250-12/625-D48
TWR-3.3/4250-15/500-D24
TWR-3.3/4250-15/500-D48
4 Amps
2 Amps
4 Amps
2 Amps
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