UG:017
vicorpower.com
Applications Engineering: 800 927.9474
Page 15
Trim Control
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Jumper block J09 configures trimming.
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With no jumpers installed, neither the trim potentiometer nor the test point for external trim con-
trol is connected to the TR net. Note that the paralleling connectors always connect to the TR net.
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With a jumper loaded across J09.1 and J09.2, the trim potentiometer R26 is
connected as a rheostat between the TR node and SG.
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With a jumper loaded across J09.3 and J09.4, the external trim test point is
connected to the TR node.
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The DCM contains an internal pull-up resistor to VCC (3.3V nominal). When V
IN
is applied to the DCM
it samples the TR node voltage. If it has pulled up to VCC, the DCM disables trimming as long as it
has input power, and the programmed trim condition will be nominal rated VOUT of the DCM model.
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If the TR node is not permitted to pull-up to VCC when V
IN
is applied, trimming is enabled for as long
as the DCM has input power.
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Note: Any load on the TR node may cause the DCM to select trim mode when V
IN
is applied,
including: the external trim testpoint (if selected with the jumper block), the trim potentiometer
(if selected with the jumper block), and other DCM evaluation boards attached to the
paralleling connectors.
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The trim potentiometer adds a variable resistance between the TR node and SG, from between
0
Ω
nominal, to the value of the potentiometer (500k
Ω
). This resistance range will generate TR pin
voltages which cover the entire functional range of the TR pin. Care should be taken to ensure the
programmed trim condition is within the rated trim range of the DCM in order for the DCM to meet
specifications.
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In a parallel setup using the J02 & J03 paralleling connectors, all boards besides the top one should
have the trim jumper select block at J09 open.
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In a parallel setup with multiple DCM evaluation boards, each DCM contributes another internal
pull-up resistor to a 3.3V nominal rail. With any resistive based trimming of the TR node, the resultant
trim condition will be modified by the number of DCMs which are attached and have V
IN
applied.
Conversely with a voltage source applied to the TR node, adding additional DCMs to the system has
minimal impact on the resultant trim condition.
Fault Monitoring
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Jumper block J10 configures how the FT node is monitored.
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With no jumpers installed, neither the visible LED nor the opto-coupler is connected to the FT net.
Note that the paralleling connectors always connect to the FT net.
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With a jumper loaded across J10.3 and J10.4, the visible LED at D01 and its bias resistor network
R09 & R32 are connected to the FT node.
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With a jumper loaded across J10.1 and J10.2, the opto-coupler at M02 and its bias resistor net-
work R21 & R22 is connected to the FT node.
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The DCM FT output is intended to be directly paralleled with the FT output of other DCMs in an array.
The FT node in an array forms a “wired-OR”, where any DCM can drive the FT node high.
