PQ60120QTA12 Datasheet, PDF (10/13 Pages) SynQor Worldwide Headquarters – Quarter-brick DC/DC Converter

Technical Specification
Input: 35-75 V
Output: 12 V
Current: 12 A
Package: Quarter-brick
across the output (pins 8 and 4) to determine when it should trig-
ger, not the voltage across the converter’s sense leads (pins 7
and 5). Therefore, the resistive drop on the board should be
small enough so that output OVP does not trigger, even during
load transients.
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
between Pin 6 and Pin 5 (SENSE(-) input). For a desired decrease
of the nominal output voltage, the value of the resistor should be
( ) ^Rtrim-down ⁼
511
∆%
- 10.22
(kΩ)
where
∆% =
Vnominal – Vdesired
Vnominal
x 100%
To increase the output voltage, the user should connect a resistor
between Pin 6 and Pin 7 (SENSE(+) input). For a desired increase
of the nominal output voltage, the value of the resistor should be
( ) ^{Rtrim-up = 5.11VOUT(100+∆%) _ 511 _ 10.22 (kΩ)}
1.225∆%
∆%
where
V_OUT = Nominal Output Voltage
Figure C graphs the relationship between the trim resistor value
and Rtrim-up and Rtrim-down, showing the total range the output
voltage can be trimmed up or down.
100,000
10,000
1,000
100
10
0
2
4
6
8
10 12 14 16 18 20
% increase Vout % decrease Vout
Figure C: Trim Graph for 12.0Vout module
Note: the TRIM feature does not affect the voltage at which the
output over-voltage protection circuit is triggered. Trimming the
output voltage too high may cause the over-voltage protection cir-
cuit 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, the maximum variation of the DC value of Vout,
due to both trimming and remote load voltage drops, should not
be greater than that specified for the output voltage trim range.
PROTECTION FEATURES
Input Under-Voltage Lockout: The converter is designed to
turn off when the input voltage is too low, helping avoid an input
system instability problem, described in more detail in the appli-
cation note titled “Input System Instability”. The lockout circuitry
is a comparator with DC hysteresis. When the input voltage is ris-
ing, it must exceed the typical Turn-On Voltage Threshold value
(listed on the specification page) before the converter will turn
on. Once the converter is on, the input voltage must fall below
the typical Turn-Off Voltage Threshold value before the converter
will turn off.
Output Current Limit: The maximum current limit remains con-
stant as the output voltage drops. However, once the impedance
of the short across the output is small enough to make the output
voltage drop below the specified Output DC Current-Limit
Shutdown Voltage, the converter turns off.
The converter then enters a “hiccup mode” where it repeatedly
turns on and off at a 5 Hz (nominal) frequency with a 5% duty
cycle until the short circuit condition is removed. This prevents
excessive heating of the converter or the load board.
Output Over-Voltage Limit: If the voltage across the output
pins exceeds the Output Over-Voltage Protection threshold, the
converter will immediately stop switching. This prevents damage
to the load circuit due to 1) excessive series resistance in output
current path from converter output pins to sense point, 2) a
release of a short-circuit condition, or 3) a release of a current
limit condition. 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 the temperature at the sensed location reaches the Over-
Temperature Shutdown value. It will allow the converter to turn on
again when the temperature of the sensed location falls by the
Product # PQ60120QTA12
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Doc.# 005-2QT612C Rev. A 10/4/04
Page 10