GS-R51212
20W TRIPLE OUTPUT STEP-DOWN
SWITCHING REGULATOR
FEATURES
MTBF in excess of 200,000 hours
4V max drop-out voltage
Soft start
Reset output
Non-latching short circuit protection
Crow-bar output overvoltage protection
DESCRIPTION
The GS-R51212 is a versatile triple output, high
current, high voltage step-down switching regulator
module that provides a +5V and two isolated 12V
outputs. It is ideal for microprocessor based boards
because it powers the logic and the communication
ports and it has a Reset output for the correct
system start-up.
The integral heatsink allows a large power handling
capability and it provides also an effective shielding
to minimize EMI.
MAIN CHARACTERISTICS
Vi
Vo1
Io1
Vo2
Io2
Vo3
Io3
Input Voltage
Output Voltage
Output Current
Output Voltage
Output Current
Output Voltage
Output Current
9 to 40V
5.1V
3.5A
12V
0.1A
12V
0.1A
ABSOLUTE MAXIMUM RATINGS
Symbol
Vi
Irt
Tstg
Tcop
DC Input Voltage
Reset Output Sink Current
Storage Temperature Range
Operating Case Temperature Range
Parameter
Value
42
20
– 40 to +105
– 20 to +85
Unit
V
mA
°C
°C
June 1994
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GS-R51212
USER NOTES
Input Voltage
The recommended operating maximum DC input
voltage is 40V inclusive of the ripple voltage.
Case Grounding
The module case is internally connected to pin 2
and pin 8.
The PCB area below the module can be used as
an effective sixth side shield against EMI.
Thermal Characteristics
The case-to-ambient thermal resistance of the
GS-R51212 module is about 5°C/W. This produces
a 50°C temperature increase of the module surface
for a 10W of internal power dissipation.
Depending on the ambient temperature and/or on
the power dissipation, an additional heatsink or
forced ventilation may be required.
Input Impedance
The module has an internal capacitor connected
between the input pins in order to assure PWM
stability. This capacitor cannot handle large values
of high frequency ripple current, and it can be
permanently damaged if the primary energy source
impedance is not adequate.
The use of an external low ESR, high ripple current
capacitor located as close to the module as possi-
ble is recommended. Suitable capacitors should
have a RMS current capability of 2,5 A
RMS
with a
working voltage of 50 V
DC
and an ESR of 0,1Ω at
100 kHZ. When space is a limitation, a 22µF ce-
ramic multilayer capacitor must be connected to the
module input pins.
Module Protection
The module is protected against occasional and
permanent short circuits of the output pins to
ground, as well as against output current overload.
When the output current at 5V output exceeds the
maximum value, the output is automatically dis-
abled. After a fixed time the module starts again in
a soft mode. The cycle is repeated until the overload
condition is removed.
A crow-bar output overvoltage protection is acti-
vated when the output voltage on V
o1
exceeds
6.37V.
Output Current
The output current of the main output is 3.5A. The
max output current of the two 12V outputs is a
function of the input voltage and of the main output
current as shown in fig. 1.
If the main current is zero, no voltage will be avail-
able on the 12V outputs.
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Figure 1. Output Current Capability vs. Operat-
ing Conditions
Figure 2. Reset Operation
Figure 3. Typical application
GS-R51212
Information furnished is believed to be accurate and reliable. However, SGS-THOMSON Microelectronics assumes no responsibility for the
consequences of use of such information nor for any infringement of patents or other rights of third parties which may result from its use. No
license is granted by implication or otherwise under any patent or patent rights of SGS-THOMSON Microelectronics. Specification mentioned
in this publication are subject to change without notice. This publication supersedes and replaces all information previously supplied.
SGS-THOMSON Microelectronics products are not authorized for use as critical components in life support devices or systems without express
written approval of SGS-THOMSON Microelectronics.
© 1994 SGS-THOMSON Microelectronics – All Rights Reserved
SGS-THOMSON Microelectronics GROUP OF COMPANIES
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