Datasheet

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ULT Series
Thirty-Second-Brick Isolated DC/DC Converters
with 2:1 Wide Input Range
MDC_ULT Series.F05 Page 25 of 26
Figure 7. Trim Connections To Increase Output Voltages
Connect sense to its respective V
OUT pin if sense is not used with a remote load.
LOAD
R
TRIM UP
+VOUT
+VIN
–VIN
ON/OFF
CONTROL
TRIM
+SENSE
–VOUT
–SENSE
LOAD
R
TRIM DOWN
+VOUT
+VIN
–VIN
ON/OFF
CONTROL
TRIM
+SENSE
–VOUT
–SENSE
Figure 8. Trim Connections To Decrease Output Voltages
On/Off Control
The input-side, remote On/Off Control function can be ordered to operate with
either logic type.
Positive ("P" suffi x) logic models are enabled when the on/off pin is
left open (or is pulled high, applying +10V to +15V with respect to –Input).
Positive-logic devices are disabled when the on/off pin is pulled low (-0.7 to
0.9V with respect to –Input).
Negative (“N” suffi x) logic devices are off when pin is left open (or pulled
high, applying +10V to +15V), and on when pin is pulled low (–0.7 to +0.9V)
with respect to –Input.
NOTE: Please refer to the Functional Specs for each specifi c ULT model.
Dynamic control of the remote on/off function is best accomplished with a
mechanical relay or an open-collector/open-drain drive circuit (optically isolated
if appropriate). The drive circuit should be able to sink appropriate current (see
Performance Specifi cations) when activated and withstand appropriate voltage
when deactivated. Applying an external voltage to pin 2 when no input power is
applied to the converter can cause permanent damage to the converter.
OUTPUT VOLTAGE ADJUSTMENT
Trim Equations
Adjustable output voltage pin. If the Trim pin is left open circuit the output
voltage is set to Vo nom. Adjustment by means of the external resistor must be
possible to achieve an output voltage of Vo nom. +10% or –20%.
Connecting an external resistor between the TRIM pin and the –Sense pin
decreases the output voltage set point. The following equation determines the
required external resistor value to obtain a percentage output voltage change
of ∆%:
Rtrim-down = [(511/∆%) – 10.22] K
Where:
∆% = [(Vo set – Vdesired) / Vo set] x 100
Connecting an external resistor between the TRIM pin and the +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 ∆%:
Rtrim-up = [5.11 x Vo set x (100 +∆%) / (1.225 x ∆%) – (511 / ∆%) – 10.22] K
Where:
∆% = [(Vdesired – Vo set) / Vo set] x 100
To maintain set point accuracy, the trim resistor tolerance should be at least
± 1.0%
+Vcc
13V CIRCUIT
5V CIRCUIT
–VIN
O N /O F F
C O N TR O L
+VIN
Figure 6. Driving the Negative Logic On/Off Control Pin
(simplifi ed circuit)