19 |
P a g e
DOC-MN-007-03 VCCM600 User Manual
Vox Power Limited | Unit 2, Red Cow Interchange Estate, Ballymount, Dublin 22, D22 Y8H2, Ireland | T +353 1 4591161 | www.vox-power.com
Remote Current Programming (External Voltage Control)
The output current limit of the module can be reduced using an external voltage source connected between the COM and I
CONTROL
pins on the signals connector
as shown below. In practice this also means that the output can be used as a modulated or constant current source.
Equivalent internal circuit
Control function
In the diagram above, Vi_out is an internal voltage source that is proportional to the internal inductor current and approximates the equation,
V
I_OUT
= 4*I
OUT
/I
RATED
, where Irated is the maximum rated current for the module.
In this configuration the output current limit will approximate the following equation,
I
LIMIT
= I
RATED
*V
CTRL
/4, where I
RATED
is the maximum rated current for the module.
It is not possible to increase the maximum current limit of the module, and control voltages exceeding 4.6V will have no effect on the current limit.
When using an output module as a modulated current source, the output voltage should be manually adjusted to the maximum that will be required by the
application and this will be the upper voltage limit. Once the load is connected, the output current can then be modulated by applying a control voltage as
described above.
Note that the power-good threshold level is fixed and defined by the manually preset voltage. Hence, while the output module is limiting or modulating the
output current the PG signal may go low.
Where tight current adjustment tolerances are required, it is recommended to use external circuitry to provide closed loop control of the I
CONTROL
pin.
