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LM5170EVM-BIDIR: Current on LV-port if ISETA is 0, gate on CH1 dont close

R K
Prodigy 10 points
Part Number: LM5170EVM-BIDIR
Other Parts Discussed in Thread: LM5170-Q1, LM5170

I am working with the LM5170-Q1 EVM in boost mode. I have connected a battery 48V on the HV-port and electronic power supply on the LV-port with 12V. I want to charge the battery from power of the LV-port. The board in general il working fine. Break function is disabled (FET shorted). Aux voltage comes from 48V port.

I noticed that the gate signals of channel 1 are not 0 but slightly pulsed if ISETA = 0 (also if ISETA is slightly negative). This means there is current in the LV port of circa 50mA. On channel 2 the gate signals are 0 and there is no current. This low current is not important for high current, but if I want to work below 1A this 50mA current is not good.

I know that I can disable EN1 and EN2, but when I want to work with current below 1A I have to switch on.

What can I do to close the FET completely on channel 1 (like channel 2) when EN1 and EN2 is enabled for ISETA=0?

  • 0
    TI__Expert 7450 points

    Hello R K,

    Thank you for choosing LM5170.

    Could you please first let me know if you have followed the procedure in the user's guide to setup and run the EVM in current loop control mode?

    Thanks,

    Yinsong

  • 0 in reply to Yinsong Cai1
    Prodigy 10 points

    Hi Yinsong,

    yes, the EVM is running in current loop mode. External voltage loop is not enabled. Input and output voltage are not near the limit.

    I am wondering why channel 2 is off, but channel 1 hast current (35 - 90mA dependendetn on the LV) if ISETA = 0.

    This current is a problem if i use the board with relative low current (100mA- 2A).

    The same problem is on a second board, so the chip itself has not a problem.

    What can I do do minimize the LV-current if EN=1?

    Thank you for your support.

  • 0 in reply to R K
    TI__Expert 7450 points

    Hi R K,

    Thank you for the information.

    How much did you try setting the ISETA negative?

    Thanks,

    Yinsong

  • 0 in reply to Yinsong Cai1
    Prodigy 10 points

    Hi Yinsong,

    I had now taken a close look at the control.

    With ISETA = -1mV all FETs switch off, the input current is practically 0.

    With ISETA = 0mV channel 1 is active, approx. 50mA input current

    With ISETA = + 2mV channel 1 and channel 2 are active, approx. 80mA input current

    Unfortunately, when controlling with ISETD, duty circle 0 results in over 2mV on ISETA, so I cannot switch off the FETs with this control, but that probably cannot be changed.

    Thanks for the support.