GE Industrial Solutions EHHD024A0A HAMMERHEAD Series - Manual (Page 8)

GE
Datasheet
EHHD024A0A Series: DC-DC Converter Power Module
18 to 75V
dc
Input; 5V
dc
, 24A, 120W Output
February 28, 2014 ©2014 General Electric Corporation. All rights reserved. Page 8
Feature Descriptions (continued)
If the unit is configured with the auto-restart option (4), it will
remain in the hiccup mode as long as the overcurrent
condition exists; it operates normally, once the output
current is brought back into its specified range. The average
output current during hiccup is 10% I
O, max
.
Output Voltage Programming
Trimming allows the output voltage set point to be
increased or decreased from the default value; 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
(+)
V
O
TRIM
V
O
(-)
R
trim-down
LOAD
V
IN
(+)
ON/OFF
V
IN
(-)
R
trim-up
Figure 12. Circuit Configuration to Trim Output Voltage.
Connecting an external resistor (R
trim-down
) between the TRIM
pin and the V
O
(-) (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 ∆%
ΚΩ




−
Δ
=
−
22 . 10
%
511
down trim
R
Where
100
0 . 5
0 . 5
% × 




 −
= Δ
V
V V
desired
For example, to trim-down the output voltage of the module
by 6% to 4.7V, Rtrim-down is calculated as follows:
6 % = Δ
ΚΩ




− =
−
22 . 10
6
511
down trim
R
ΚΩ =
−
9 . 74
down trim
R
Connecting an external resistor (R
trim-up
) between the TRIM
pin and the V
O
(+) (or Sense (+)) pin increases the output
voltage set point. The following equation determines the
required external resistor value to obtain a percentage
output voltage change of ∆%:
ΚΩ




−
Δ
−
Δ ×
Δ + Ч Ч
=
−
22 . 10
%
511
% 225 . 1
%) 100 ( 0 . 5 11 . 5
up trim
R
Where
100
0 . 5
0 . 5
% × 




 −
= Δ desired
V
For example, to trim-up the output voltage of the module by
4% to 5.2V, R
trim-up
is calculated is as follows:
4 % = Δ
ΚΩ




− −
Ч
+ Ч Ч
=
−
22 . 10
4
511
4 225 . 1
) 4 100 ( 0 . 5 11 . 5
up trim
R
ΚΩ =
−
3 . 404
up trim
R
The voltage between the V
O
(+) and V
O
(–) 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
).
Thermal Considerations
The power modules operate in a variety of thermal
environments; however, sufficient cooling should be
provided to help ensure reliable operation.
Considerations include ambient temperature, airflow,
module power dissipation, and the need for increased
reliability. A reduction in the operating temperature of the
module will result in an increase in reliability.
The thermal data presented here is based on physical
measurements taken in a wind tunnel, using automated
thermo-couple instrumentation to monitor key component
temperatures: FETs, diodes, control ICs, magnetic cores,
ceramic capacitors, opto-isolators, and module pwb
conductors, while controlling the ambient airflow rate and
temperature. For a given airflow and ambient temperature,
the module output power is increased, until one (or more) of
the components reaches its maximum derated operating
temperature, as defined in IPC-9592. This procedure is then
repeated for a different airflow or ambient temperature until
a family of module output derating curves is obtained.