Input:
Outputs:
Current:
Package:
35-75V
5.0V & 3.3V
60W
Quarter-brick
Technical Specification
age up or down.
cycle until the short circuit condition is removed. This prevents
excessive heating of the converter or the load board.
Resistor values in Kohms for the desired increase/decrease (typi-
cal) in output voltage (%)
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.
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.
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.
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
amount of the Over-Temperature Shutdown Restart Hysteresis
value.
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.
APPLICATION CONSIDERATIONS
Input System Instability: This condition can occur because
any DC/DC converter appears incrementally as a negative
resistance load. A detailed application note titled “Input
System Instability” is available on the SynQor web site
(www.synqor.com) which provides an understanding of why
this instability arises, and shows the preferred solution for cor-
recting it.
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.
Application Circuits: Figure D below provides a typical cir-
cuit diagram which details the input filtering and voltage trim-
ming.
The converter then enters a “hiccup mode” where it repeatedly
turns on and off at a 5 Hz (nominal) frequency with a 5% duty
Vin(+)
5.0 Vout(+)
Iload
Rtrim-up
Electrolytic
Capacitor
Trim
Cload
External
Input
47µF
Vin
OP RTN
ON/OFF
Filter
or
Rtrim-down
Cload
_
Iload
3.3 Vout(+)
Vin( )
Figure D: Typical application circuit (negative logic unit, permanently enabled).
Product # DQ65033QMA06
Phone 1-888-567-9596
Doc.# 005-2DQ653E Rev. H
7/7/04
Page 13
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