GE Industrial Solutions QBDW025A0B Barracuda Series - Manual (Page 11)

GE
Data Sheet
QBDW025A0B Barracuda Series; DC-DC Converter Power Modules
36-75Vdc Input; 12.0Vdc, 25.0A, 300W Output
May 9, 2013 ©2012 General Electric Company. All rights reserved. Page 11
values. These values are adjustable via PMBus. PG is
asserted when the module’s output voltage is above the
POWER_GOOD_ON value, and PG is de-asserted if any
condition such as overtemperature, overcurrent or loss of
regulation occurs that would result in the output voltage
going below the POWER_GOOD_OFF value.
The PG signal, provided on pin C2, is implemented with an
open-drain node, pulled up via a 10kΩ resistor to 3.3V
internally. For Positive Logic PG (default), the PG signal is HI,
when PG is asserted, and LO, when the PG is de-asserted.
For Negative Logic PG, the PG signal is LO, when PG is
asserted, and HI, when the PG is de-asserted.
The PMBus command MFR_PGOOD _POLARITY is used to set
the logic polarity of the signal.
If not using the Power Good feature, the pin may be left N/C.
Trim, Output Voltage Programming
Trimming allows the output voltage set point to be
increased or decreased; this is accomplished by connecting
an external resistor between the TRIM pin and either the
V
O
(+) pin or the V
O
(-) pin.
V
O
(+)
T/C1
V
O
(-)
R
trim-down
LOAD
QBDW033A0B
R
trim-up
Figure 16. Circuit Configuration to Trim Output Voltage.
Connecting an external resistor (R
trim-down
) between the T/C1
pin and the Vo(-) (or Sense(-)) pin decreases the output
voltage set point. To maintain set point accuracy, the trim
resistor tolerance should be ±1.0%.
The following equation determines the required external
resistor value to obtain a percentage output voltage change
of ∆%.








 22 . 10
%
511
down trim
R
Where
100
0 . 12
0 . 12
%
 




 
 
V
V V
desired
For example, to trim-down the output voltage of the module
by 20% to 9.6V, Rtrim-down is calculated as follows:
20 %
 





 

22 . 10
20
511
down trim
R
 

k R
down trim
3 . 15
Connecting an external resistor (R
trim-up
) between the T/C1
pin and the V
O
(+) (or Sense (+)) pin increases the output
voltage set point. The following equations determine the
required external resistor value to obtain a percentage
output voltage change of ∆%:








 
   


22 . 10
%
511
% 225 . 1
%) 100 ( 0 . 12 11 . 5 V
R
up trim
Where
100
0 . 12
0 . 12
%
 




 
 
V
V V
desired
For example, to trim-up the output voltage of the module by
5% to 12.6V, R
trim-up
is calculated is as follows:
5 %
 





 

  


22 . 10
5
511
5 225 . 1
) 5 100 ( 0 . 12 11 . 5
up trim
R
 

8 . 938
up trim
R
The voltage between the Vo(+) and Vo(–) terminals must not
exceed the minimum output overvoltage protection value
shown in the Feature Specifications table. This limit includes
any increase in voltage due to remote-sense compensation
and output voltage set-point adjustment trim.
Although the output voltage can be increased by both the
remote sense and by the trim, the maximum increase for
the output voltage is not the sum of both. The maximum
increase is the larger of either the remote sense or the trim.
The amount of power delivered by the module is defined as
the voltage at the output terminals multiplied by the output
current. When using remote sense and trim, the output
voltage of the module can be increased, which at the same
output current would increase the power output of the
module. Care should be taken to ensure that the maximum
output power of the module remains at or below the
maximum rated power (Maximum rated power = V
O,set
x
I
O,max
).