Technical Specification
trim resistance (ohms)
MQFL-28V-06S
Output:
6V
Current:
17A
100,000
ad
pu
va
bl
ic n
at ce
io d
n
1,000
OUTPUT VOLTAGE TRIM:
If desired, it is possible to increase
the MQFL converter’s output voltage above its nominal value. To
do this, use the +SENSE pin (pin 10) for this trim function instead
of for its normal remote sense function, as shown in Figure D.
In this case, a resistor connects the +SENSE pin to the –SENSE
pin (which should still be connected to the output return, either
remotely or locally). The value of the trim resistor should be chosen
according to the following equation or from Figure E:
Rtrim = 100 x
10,000
where:
Vnom = the converter’s nominal output voltage,
Vout = the desired output voltage (greater than Vnom), and
Rtrim is in Ohms.
[
Vnom
Vout – Vnom – 0.025
]
100
0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
Increase in Vout (V)
As the output voltage is trimmed up, it produces a greater voltage
stress on the converter’s internal components and may cause
the converter to fail to deliver the desired output voltage at the
low end of the input voltage range at the higher end of the load
current and temperature range. Please consult the factory for
details. Factory trimmed converters are available by request.
Figure E:
Output Voltage Trim Graph
INPUT OVER-VOLTAGE SHUTDOWN:
The MQFL converter
also has an over-voltage feature that ensures the converter will be
off if the input voltage is too high. It also has a hysteresis and time
delay to ensure proper operation.
BACK-DRIVE CURRENT LIMIT:
Converters that use MOSFETs as
synchronous rectifiers are capable of drawing a negative current
from the load if the load is a source of short- or long-term energy.
This negative current is referred to as a “back-drive current”.
Conditions where back-drive current might occur include paralleled
converters that do not employ current sharing, or where the current
share feature does not adequately ensure sharing during the
startup or shutdown transitions. It can also occur when converters
having different output voltages are connected together through
INPUT UNDER-VOLTAGE LOCKOUT:
The MQFL converter has
an under-voltage lockout feature that ensures the converter will be
off if the input voltage is too low. This lockout only appears when
the boost-converter is not operating. The threshold of input voltage
at which the converter will turn on is higher that the threshold at
which it will turn off. In addition, the MQFL converter will not
respond to a state of the input voltage unless it has remained in
that state for more than about 200µs. This hysteresis and the delay
ensure proper operation when the source impedance is high or in
a noisy environment.
1
2
3
4
5
6
+VIN
External bulk capacitor
IN RTN
ENA 1
ENA 2 12
SHARE 11
+SNS 10
-SNS 9
28 Vdc
+
STABILITY
SYNC OUT
SYNC IN
R
STABILITY
MQFL
R
TRIM
C
STABILITY
open
means
on
OUT RTN 8
+VOUT 7
Load
+
Figure D:
Typical connection for output voltage trimming.
Phone 1-888-567-9596
Product # MQFL-28V-06S
www.synqor.com
Doc.# 005-0005182 Rev. 1
04/16/09
Page 13
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