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UCD90320U: Current monitoring resolution ~15mA

Part Number: UCD90320U
Other Parts Discussed in Thread: INA190,

I have a UCD90320U which is set up with multiple MON pins as current monitors. I am using the INA190A5 current sense amplifier and a variety of shunt resistor sizes. There are no additional resistor dividers between the INA190 and the sequencer.

When I poll the currents for these rails, the sequencer returns current readings in 15.625mA steps. This is regardless of what Iout Cal Gain is used (if I use a different Iout Cal Gain value, the current is scaled accordingly, but the returned readings are still in 15.625mA steps). 15.625mA is pretty poor resolution for a current monitor, if I have a rail that is only meant to draw a few 10s of mA, this makes it difficult to set proper warn/fault limits. Additionally, the sequencer returns up to 31.25mA readings for rails that are completely off, and should read near zero currents.

I am confident that the analog voltage out of the INA190 corresponds properly to currents that are non-15.626mA multiples, and is at a near 0 voltage when currents are zero. Is there a firmware setting that I am missing in the UCD90320U configuration? Or is this a limitation of the chip itself

  • HI

    yes, 15.626mA is the resolution of the current sensing from the device.

    If much better resolution is desired, you can use voltage monitor to monitor the voltage and convert the current from outside of the UCD basically, treat it as a voltage instead of current.