Advance Data Sheet
October 1999 18 Vdc to 36 Vdc and 36 Vdc to 75 Vdc Input; 10 W
SMLC/SMLW010 Single-Output Low-Profile Power Modules:
Tyco Electronics Corp. 7
Safety Considerations (continued)
SMLW Modules
For safety-agency approval of the system in which the
power module is used, the power module must be
installed in compliance with the spacing and separation
requirements of the end-use safety agency standard,
i.e.,
UL
1950,
CSA
C22.2 No. 950-95, and VDE 0805
(EN60950, IEC950).
If the input source is non-SELV (ELV or a hazardous
voltage greater than 60 Vdc and less than or equal to
75 Vdc), for the module's output to be considered
meeting the requirements of safety extra-low voltage
(SELV), all of the following must be true:
■The input source is to be provided with reinforced
insulation from any other hazardous voltages, includ-
ing the ac mains.
■One VI pin and one V O pin are to be grounded or both
the input and output pins are to be kept floating.
■The input pins of the module are not operator acces-
sible.
■Another SELV reliability test is conducted on the
whole system, as required by the saf ety agencies, on
the combination of supply source and the subject
module to verify that under a single fault, hazardous
voltages do not appear at the module's output.
Note: Do not ground either of the input pins of the
module without grounding one of the output
pins. This may allow a non-SELV voltage to
appear between the output pins and ground.
The power module has extra-low v oltage (ELV) outputs
when all inputs are ELV.
The input to these units is to be provided with a maxi-
mum 5 A normal-blow fuse in the ungrounded lead.
Feature Descriptions
Overcurrent Protection
To provide protection in a fault (output overload) condi-
tion, the unit is equipped with internal current-limiting
circuitry and can endure current limiting for an unlim-
ited duration. At the point of current-limit inception, the
unit shifts from voltage control to current control. If the
output voltage is pulled very low during a severe fault,
the current-limit circuit can exhibit either foldback or
tailout characteristics (output-current decrease or
increase). The unit operates normally once the output
current is brought back into its specified range.
Remote On/Off
Positiv e logic remote on/off turns the module on during
a logic-high voltage on the remote ON/OFF pin, and off
during a logic low.
To turn the power module on and off, the user must
supply a switch to control the voltage between the
on/off terminal and the VI(–) terminal (Von/off). The
switch may be an open collector or equivalent (see
Figure 4). A logic low is Von/off = –0.7 V to 1.2 V. The
maximum Ion/off during a logic low is 1 mA. The switch
should maintain a logic-low voltage while sinking 1 mA.
During a logic high, the maximum Von/off generated by
the power module is 6 V. The maximum allowable leak-
age current of the switch at Von/off = 6 V is 50 µA.
The module has internal capacitance to reduce noise
at the ON/OFF pin. Additional capacitance is not gen-
erally needed and may degrade the start-up character-
istics of the module.
8-758(C).a
Figure 4. Remote On/Off Implementation
Output V oltage Adjustment
Output voltage set-point adjustment allows the user to
increase or decrease the output voltage set point of a
module. This is accomplished by connecting an exter-
nal resistor between the TRIM pin and either the VO(+)
or V O(–) pins. With an external resistor between the
TRIM and VO(+) pins (Radj-down), the output voltage set
point (VO, adj) decreases (see Figure 5). The following
equation determines the required external resistor
v alue to obtain an output voltage change from V O , nom to
VO, adj:
where Radj-down is the resistance value connected
between TRIM and VO(+), and G, H, and L are defined
in the table below.
+
Ion/off
–
Von/off
REMOTE
ON/OFF
VI(+)
VI(–)
Radj-down VO adj,L–()G
VO nom,VO adj,–()
--------------------------------------- H–Ω=