Other Parts Discussed in Thread: LM5175,
Tool/software: WEBENCH® Design Tools
Hi,
We are trying to use LM5175-Q1 as a programmable constant current source with output current selectable 0-20 A. The LM5175 Rsns is used to limit output current, but resistance is extremely low (we find 3.3 mOhm in our application according to the LM5175 datasheet).
The datasheet reads:
The LM5175-Q1 provides optional average current limiting capability to limit either the input or the output current
of the DC/DC converter. The average current limiting circuit uses an additional current sense resistor connected
in series with the input supply or output voltage of the converter. A current sense gm amplifier with inputs at the
ISNS(+) and ISNS(-) pins monitors the voltage across the sense resistor and compares it with an internal 50 mV
reference. If the drop across the sense resistor is greater than 50 mV, the gm amplifier gradually discharges the
soft-start capacitor. When the soft-start capacitor discharges below the 0.8-V feedback reference voltage VREF,
the output voltage of the converter decreases to limit the input or output current. The average current limiting
feature can be used in applications requiring a regulated current from the input supply or into the load. The target
constant current is given by Equation 4:
(4)
The average current loop can be disabled by shorting the ISNS(+) and ISNS(-) pins together.
Are we missing something? How can output current be limited/controlled/programmed using such small resistance? Any help is welcome.
