DRV120: DRV120 Hot Swap device failure

gotmilk

Part Number: DRV120
Other Parts Discussed in Thread: DRV110,

Hi part of f the requirement is the solenoid be hot swap. Using a DRV120EVM board, while hot swapping causes the device to fail.

Performing the identical test on a EVM110 no failures occurred. Comparing the two EVMS the mosfet used on the DRV110 has a 600v rating from drain to source.

Is it possible to achieve identical performance with a DRV120?

The input is voltage is 24v's the hold current is set to 50ma (measures with a current probe) , the hit current pot is fully counter clock wise and

the PWM frequency is set to minimize squeal. The maximum DC current draw from the solenoid is ~130ma's with a resistant of 180ohms.

btw do you have any advice on choosing the optimal PWM frequency?

thanks

over 6 years ago

0 Grant Falkenburg over 6 years ago

TI__Intellectual 1965 points

Hi gotmilk,

It is never recommended to open circuit an inductor while it's charged. Doing so typically generates kilovolts in order to maintain continuity of the inductor's current. That said, it is no surprise that the DRV120 failed. In your application, is it possible to solder a small diode to your solenoid to allow the current to circulate when the solenoid is removed?

As for PWM frequency, I recommend the maximum frequency 25kHz as it is out of the audio range. If the duty cycle is not stable at this frequency, I recommend lowering the frequency until the duty cycle is stable.

Let me know if you have any further questions.

Best,

Grant

0 James Bond over 6 years ago

Intellectual 380 points

Hi the demo board includes a diode in parallel with the solenoid, did you mean directly to the solenoid wires?

other options

thanks

0 Grant Falkenburg over 6 years ago in reply to James Bond

TI__Intellectual 1965 points

Hi James,

Yes. If you can, connect a diode directly to the solenoid such that the diode is still connected when you remove the solenoid. This will allow the current in the solenoid to decay in a controlled manner without causing large voltage spikes.

Best,
Grant

0 James Bond over 6 years ago in reply to Grant Falkenburg

Intellectual 380 points

Hi The current drops then recovers, I prefer for this not to occur, is there a solution

Yellow current, Green is Out pin of the DRV

0 Grant Falkenburg over 6 years ago in reply to James Bond

TI__Intellectual 1965 points

Hi James,

In what context does this current drop occur? How often does it occur? Is there anything you can think of that is causing it? Does this occur on the DRV110 or DRV120?

Regarding your other question of hot-swapping the solenoid, you can also use the enable pin to disable the device before taking it out.

Best,
Grant

0 Grant Falkenburg over 6 years ago in reply to Grant Falkenburg

TI__Intellectual 1965 points

Hi James,

On close inspection of your waveform, it looks like there are some current spikes that may be interfering with the SENSE pin. Are you using a filter on the SENSE pin? If not, please try adding a 1kOhm and 100pF RC filter from the sense resistor to the SENSE pin.

Best,
Grant

0 James Bond over 6 years ago in reply to Grant Falkenburg

Intellectual 380 points

Hi Photo was taken using the DRV120EVM, the IC does not have provision for a sense line.

0 Grant Falkenburg over 6 years ago in reply to James Bond

TI__Intellectual 1965 points

Hi James,

R7 and C1 on the DRV120EVM are where the sense filter is. Can you populate R7 with 1kOhm and C1 with 100pF? If that does not help with PWM stability, you can try using a larger capacitor (1nF).

Best,

Grant

0 James Bond over 6 years ago in reply to Grant Falkenburg

Intellectual 380 points

Hi Grant so far looks ok

thanks

0 Grant Falkenburg over 6 years ago in reply to James Bond

TI__Intellectual 1965 points

Hi James,

No problem. Let me know if there's anything else I can help with.

Best,

Grant

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DRV120: DRV120 Hot Swap device failure