Product # PQ60012QPA60
Phone 1-888-567-9596
Doc.# 005-2QP621F Rev. C
3/23/07
Page 11
T
Technical S
echnical Specification
pecification
Input:
Output:
Current:
PPackage:
ackage:
36-75 V
1.2 V
60 A
Quarter-brick
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
amount of the Over-Temperature Shutdown Restart Hysteresis
value.
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.
Application Circuits: Figure E provides a typical circuit dia-
gram which details the input filtering and voltage trimming.
Input Filtering and External Capacitance: Figure F pro-
vides a diagram showing the internal input filter components.
This filter dramatically reduces input terminal ripple current,
Vin
External
Input
Filter
Trim
Vin(+)
Iload
Cload
L
Vout(+)
Rtrim-up
or
Rtrim-down
Vsense(+)
ON/OFF
Vin(_)
Vin(+)
Vin(_)
Vout(_)
Vsense(_)
Electrolytic
Capacitor
47F
Figure E: Typical application circuit (negative logic unit, permanently enabled).
C