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DRV120: Output current not meeting expected value

Ian Watson
Prodigy 10 points
Part Number: DRV120
Other Parts Discussed in Thread: DRV110,

We are using three Staiger spider microvalve VA 204-508 24V with three DRV120A valve drivers. I have a Peak current set of 100mA and a hold current of 50mA.

Rpeak - 162k

Rhold - 133k

Rosc - 160k (25kHz)

Ckeep - 10uF (750ms)

 

The peak current I am seeing is 63mA which is okay as this is the full current for the valve.

The hold current I am getting is about 36mA, but has been as low as 30mA on one device on one board which resulted in the valve not holding open when under pressure.

Is there something incorrect in the datasheet w.r.t. to the calculations? Or is this within the expected tolerance?

I have also been testing with a resistive load equivalent to the valve of 360R, this is showing an average current of ~6mA with a low mark space ratio on the output of the FET.

I've also notice that the data sheet refers to a SENSE pin, (which doesn't exist) and the Internal RSense value is not specified.

  • 0
    TI__Mastermind 37683 points

    Hi Ian,

    Ian Watson said:
    I've also notice that the data sheet refers to a SENSE pin, (which doesn't exist) and the Internal RSense value is not specified.

    This may a problem with the datasheet. The DRV120 is a similar device to the DRV110 which is a device with external MOSFET. Since these devices are very similar, much of the datasheet information is shared. We will work on updating the datasheet. Thank you for bringing this to our attention.

    Ian Watson said:

    The hold current I am getting is about 36mA, but has been as low as 30mA on one device on one board which resulted in the valve not holding open when under pressure.

    Is there something incorrect in the datasheet w.r.t. to the calculations? Or is this within the expected tolerance?

    I checked the calculation given in the datasheet and it matches your values. Can you share your schematic? Also, can you share any waveforms you have taken?

  • 0 in reply to Pablo Armet
    Prodigy 10 points

    After further investigation there were some ESD diodes on the out pin else where in the circuit. Removing these resolved the issue.

    Thanks,