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TPL7407LA: Driving Solenoid with 400mA current rating at 18V using 2 channels

Neet
Intellectual 612 points
Part Number: TPL7407LA
Other Parts Discussed in Thread: ULN2003A

Hello TI Team,

We want to directly drive a Solenoid Coil that operates at 18V & 400mA current. I am planning to parallel two channels on TPL74074LA device for driving two a these coils. At any given point of time only one coil shall be operational by design. I however would like to confirm any issues when using such a configuration? Are we missing out anything obvious? Any additional protection measures we should implement?

There shall be a total of 3 loads connected to the TPL7407LA:

  1. Coil 1: 18V & 400mA active for 2 seconds maximum, operated 10 times per day
  2. Coil 2: 18V & 400mA active for 2 seconds maximum, operated 10 times per day
  3. Relay 1: 12V & ~50mA active for 120 seconds maximum, operated 10 times per day

Kindly guide any other device that shall be better suited for robust implementation if TPL7407LA is not a robust choice, the location of device installation is not very accesisble.

Thank you!

  • 0
    TI__Mastermind 29480 points

    Hi Neet,

    No issues here with TPL7407LA, just please be sure to connect the COM pin to 18V (or higher).

    However, if you're anticipating negative voltages on the outputs (not sure why you would be, but just in case) then ULN2003A would be a better fit.

    Thanks,

    Patrick

  • 0 in reply to Patrick Shalton
    Intellectual 612 points

    Hello Patrick,

    The occassional overshoot & inductive kickbacks due to 400mA Solenoid load should not posses any long term reliability issues, right?

    Would you suggest some Application Notes for additional safety measures we can implement at the design stage?

    Thanks!

  • +1 in reply to Neet
    TI__Mastermind 29480 points

    Hi Neet,

    There is an integrated clamp diode from OUT to COM that will dissipate inductive kickbacks and any overshoot, so no issues there as long as things are kept within Recommended (Absolute for current) Operating Conditions.

    And, since low-side switches are fairly simple and robust and contain integrated protection features, there aren't any Application Notes focused on them. As long as no overcurrent, negative voltage, or overvoltage on COM will take place, TPL7407 will be fine.

    Thanks,

    Patrick

  • 0 in reply to Patrick Shalton
    Intellectual 612 points

    Hello Patrick,

    Two quick questions:

    1. Upto what amount of input ripple is acceptable to the internal LDO of TPL7407?
      (We have a full bridge rectifier with capacitor on the output of a transformer (50Hz) generating upto 0.8V ripple is this acceptable input for the LDO of the TPL7407? Kindly guide)
    2. In another use case - we would like to know if we can reliably power the COM pin of the TPL7407LA with 5V DC supply that is powering our MCU?
  • 0 in reply to Neet
    TI__Mastermind 29480 points

    Hi Neet,

    1. I don't think 50Hz ripple should be an issue. About magnitude, please see 2.

    2. At least 6.5V on the COM pin is recommended, but please see Section 9 of the data sheet below. 5V will be ok if you are ok with a higher Rdson. If not, then I recommend using ULN2003A.

    Thanks,

    Patrick

  • 0 in reply to Patrick Shalton
    Intellectual 612 points

    Hello ,

    The datasheet also mentions that there is a LDO that converts 6.5V to 30V input into a regulatd 5.3V output that is then used for gate driving, in this case:

    1. Will this internal LDO work with 5V?
    2. Can we keep the COM pin floating & instead use external Flyback Diodes?
    3. What is the pulsed current rating for individual channel?
    4. Any additional safety provisions for the output of the TPL7407 when using solenoid load?

    Kindly guide.

  • 0 in reply to Neet
    TI__Mastermind 29480 points

    Hi Neet,

    1. Yes, but the driving strength will be reduced and thus the RON/VOH will be increased.

    2. No, this device needs the COM pin powered to drive the FETs. For a device that doesn't need a voltage source on COM, please see ULN2003A.

    3. Please see the attached Figure 5, the maximum rated value in the data sheet is 600mA (channels can be paralleled to increase current capability), but this could be higher if the ambient temperature is low.

    4. No additional measures, the internal flyback diodes are rated for 500mA so please make sure the current through them won't exceed that.

    Thanks,

    Patrick