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48 V
5.0 V
20 A
Quarter-brick
Product # PQ60050QGA20
Phone 1-888-567-9596
Doc.# 005-2QG650D Rev. E
07/15/09
Page 10
Technical Specification
Input:
Output:
Current:
Package:
48 V
5.0 V
20 A
Quarter-brick
OUTPUT VOLTAGE TRIM (Pin 6): The TRIM input permits the
user to adjust the output voltage across the sense leads up or down
according to the trim range specifications.
To decrease the output voltage, the user should connect a resistor
betweenPin6andPin5(SENSE(-)input).Foradesireddecreaseof
the nominal output voltage, the value of the resistor should be
Rtrimdown =
(511) -10.22 (kΩ)
%
where
% = V
nominal
–Vdesired x100%
Vnominal
To increase the output voltage, the user should connect a resistor
betweenPin6andPin7(SENSE(+)input).Foradesiredincreaseof
the nominal output voltage, the value of the resistor should be
Rtrimup =
(5.11VOUT(100+%)_511_10.22)(kW)
1.225%
%
where
VOUT=NominalOutputVoltage
FigureCgraphstherelationshipbetweenthetrimresistorvalue
andRtrim-upandRtrim-down,showingthetotalrangetheoutput
voltage can be trimmed up or down.
Figure C: Trim Graph for 5.0 Vout module
Note: the TRIM feature does not affect the voltage at which the
output overvoltage protection circuit is triggered. Trimming the
output voltage too high may cause the overvoltage protection circuit
to engage, particularly during transients.
It is not necessary for the user to add capacitance at the Trim pin.
The node is internally bypassed to eliminate noise.
Total DC Variation of Vout: For the converter to meet its full
specifications,themaximumvariationoftheDCvalueofVout,dueto
both trimming and remote load voltage drops, should not be greater
than that specified for the output voltage trim range.
PROTECTIONFEATURES
Input Under-Voltage Lockout:Theconverterisdesignedtoturn
off when the input voltage is too low, helping avoid an input system
instability problem, described in more detail in the application note
titled“InputSystemInstability”.Thelockoutcircuitryisacompara-
tor with DC hysteresis. When the input voltage is rising, it must
exceedthetypicalTurn-OnVoltageThresholdvalue(listedonthe
specificationpage)beforetheconverterwillturnon.Oncethecon-
verterison,theinputvoltagemustfallbelowthetypicalTurn-Off
VoltageThresholdvaluebeforetheconverterwillturnoff.
Output Current Limit:Themaximumcurrentlimitremainscon-
stant as the output voltage drops. However, once the impedance
of the short across the output is small enough to make the output
voltagedropbelowthespecifiedOutputDCCurrent-LimitShutdown
Voltage,theconverterturnsoff.
The converter then enters a “hiccup mode” where it repeatedly
turnsonandoffata5Hz(nominal)frequencywitha5%dutycycle
until the short circuit condition is removed. This prevents excessive
heating of the converter or the load board.
Output Over-Voltage Limit:Ifthevoltageacrosstheoutputpins
exceedstheOutputOver-VoltageProtectionthreshold,theconverter
will immediately stop switching. This prevents damage to the load
circuitdueto1)excessiveseriesresistanceinoutputcurrentpath
fromconverteroutputpinstosensepoint,2)areleaseofashort-
circuitcondition,or3)areleaseofacurrentlimitcondition.Load
capacitance determines exactly how high the output voltage will
rise in response to these conditions. After 200 ms the converter will
automatically restart.
Over-Temperature Shutdown: A temperature sensor on the
converter senses the average temperature of the module. The
thermal shutdown circuit is designed to turn the converter off when
thetemperatureatthesensedlocationreachestheOver-Temperature
Shutdown value. It will allow the converter to turn on again when the
temperatureofthesensedlocationfallsbytheamountoftheOver-
TemperatureShutdownRestartHysteresisvalue.
100,000
10,000
1,000
100
10
0
2
4
6
8
10
12
14
16
18
20
Tri
m
R
esi
stance
(k
O
hms)
% decrease Vout
% increase Vout