Crane Aerospace & Electronics Power Solutions
MOR Single and Dual DC/DC Converters
28 VOLT INPUT – 120 WATT
TRIM FORMULAS
HOW TO USE FUNCTIONS
Trim Up:
V
POSITIVE INPUT AND INPUT COMMON
o
α
=
, 1.0 ≤ α ≤ 1.1
V
Steady state voltage range is 16 to 40 VDC. Transient range is 40
to 50 V for a maximum of 120 msec. Low voltage lockout prevents
the units from operating below approximately 15.5 VDC input
voltage to keep system current levels smooth, especially during
initialization or re-start operations. All models include a soft-start
function to prevent large current draw and minimize overshhoot.
o nominal
V
o
(
– 1 • 20
)
2.5
R (kΩ) =
T
– 50
(α -1)
Example:
CASE AND EXTERNAL INPUT FILTERS
Internal 500 V capacitors are connected between the case and
input common and between the case and output common. See
Figure 3.
V
= 5.0, V = 5.25, α = 1.05, R = 390 kΩ
o nominal
o
T
Trim Down:
V
o
α
=
, 0.6 ≤ α ≤ 1.0
1, 2, 3
V
10, 11, 12
1
o nominal
Positive Input
Positive Output
Positive Input
MOR
FME28-461
EMI Filter
Single or Dual
Output
28V
50 • α – 30
1 – α
R (kΩ) =
T
4, 5, 6
Input Common
7, 8, 9
2
Input Common
Output Common
Example: V
= 5.0,V = 4.5, α = 0.9, R = 150 kΩ
o nominal
o
T
Case
Chassis Ground
INHIBIT 1 AND 2
Two inhibit terminals disable switching, resulting in no output and
FIGURE 3: EXTERNAL FILTER CONNECTION
very low quiescent
input current. The
two inhibit pins allow
access to an inhibit
function on either
side of the isolation
barrier to help main-
tain isolation.
Positive
Input
Interpoint’s FME filters are recommended to meet CE03 require-
ments for reflected input line current. When using an external input
filter it is important that the case of the filter and the case of the
converter be connected through as low as an impedance as
possible. Direct connection of the baseplates to chassis ground is
the best connection. If connected by a single trace, the trace should
be as wide as it is long.
Inhibit 1
VCC
Input
Common
MOR Input Side
An open collector is
required for inter-
facing with both of
TRIM
FIGURE 6: INHIBIT – INPUT SIDE
Both single and dual output models include a trim function. Output
voltage can be trimmed from 60% up to 110% of nominal V out .
When trimming up, do not exceed the maximum output power.
When trimming down, do not exceed the maximum output current.
See Figure 4.
the inhibit pins. Applying an open-collector TTL logic low to either
inhibit pin will inhibit the
converter. Applying an
open collector TTL logic
high or leaving the pins
open will enable the
VS
~
~
Voltage
E/A
Current
Limit
On dual models the positive output is regulated and the negative
output is transformer coupled (cross-regulated) to the positive
output. When trimming the duals, both output voltages will be
adjusted equally. See Figure 5.
converter. Inhibit
1
is
referenced
to
Input
Feedback
Common, while Inhibit 2
is referenced to Sense
Return on the output side.
Inhibit 2
Sense
Return
Trim
3
RT
7
10
Trim
RT
10
MOR Output Side
TRIM UP
TRIM UP
7
8
Positive Output
Positive Sense
Positive Output
The open circuit voltage
for Inhibit 1 is 13 V and for
MOR
Single
Output
FIGURE 7: INHIBIT – OUTPUT SIDE
MOR
Dual
Output Common
Output
TRIM DOWN
9
8
Inhibit 2 it is 8 V. Float the inhibit pin(s) if not used. The required
logic low voltage level is 0.2 V maximum.
Sense Return
Output Common
9
Negative Output
TRIM
DOWN
FIGURE 4: TRIM – SINGLE
FIGURE 5: TRIM – DUAL
See Figures 6 and 7.
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