Remote ON/OFF Function
APPLICATION NOTES
To lower the converter output voltage a resistor must be
placed between the Trim pin and -Vout pin as shown in
Figure 3.
+ Vout
+ Sense
ON/OFF
Protective Functions
Temperature Shutdown
The over temperature shutdown feature of the SLC100
will cause the unit to shutdown at a typical pwb tem-
perature of TBD. This protective feature is comprised
of a thermistor in the units control loop. At a tempera-
ture of TBD this circuit will cause the PWM to go into
an idle mode, resulting in no output from the converter
and preventing damage to the converter components.
When the temperature of the unit drops below TBD the
fault condition will clear and the converter will resume
normal operation. If the cause of the over temperature
condition is not identified and corrected the unit will
continue to cycle on and off indefinitely.
+ Vin
SLC100
(Top View)
Trim
-
Sense
Load
R
T
- Vin
- Vout
Figure 3 – Trim Down Circuit
The resistance value required to achieve the desired
amount of positive/negative trim can be determined by
referring to the trim table for each model. If trimming is
not desired then the Trim pin may be left open.
In addition to the resistor values provided in the trim
tables, the following equations can be use to calculate
the required resistor value for a desired output voltage.
These equations apply for the 1.5V and above models.
For 1.2V models the trim tables must be used.
Input Under-Voltage Shutdown
The nominal input voltage for the SLC100 is 48Vdc.
Once turned on reducing the input voltage to 32.5 Vdc
nominal will shut down the device. At an input voltage
less than 32.5V the under-voltage sensing circuit will
send a signal to the PWM causing it to go into idle
mode. This will result in no output from the converter,
protecting the unit from a high input current condition.
When the input voltage returns to a level above 32.5V
the unit will return to normal operation. The unit will
typically turn on at an input voltage of 33.7V nominal
as indicated on the Product Data Sheet. This is due to
hysterisis designed into the protective circuit to prevent
excessive cycling of the converter.
Remote ON/OFF Control Function
The SLC100 is equipped with a primary ON/OFF pin
used to remotely turn the converter on or off via a system
signal. The input is TTL open-collector and/or FET open-
drain compatible. For the positive logic model a system
logic low signal will turn the unit off. For negative logic
models a system logic high signal will turn the converter
off. For negative logic models where no control signal
will be used the ON/OFF pin should be connected
directly to –Vin to ensure proper operation. For positive
logic models where no control signal will be used the
ON/OFF pin should be left open.
Brick Wall Current Limiting
To protect against fault or short-circuit conditions on
the output, each module is equipped with current-limit-
ing circuitry designed to provide continuous protection.
After reaching the current limit point (typically 20%
above the rated output current), the voltage will range
between its rated value and zero, depending upon the
amount of overload. The unit will remain in operation
continuously during this period down to a short-circuit
condition. Once the short or overload has been elimi-
nated, the output voltage will return to normal without
cycling the input power.
+ Vin
+ Vout
+ Sense
ON/OFF
SLC100
(Top View)
-
Trim
Sense
- Vout
- Vin
Control Signal
Figure 4 – Remote ON/OFF Control Circuit
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MURATA-PS [ MURATA POWER SOLUTIONS INC. ]
