DRV103H output fault

If one of the TE engineers would like to contact me (a humble mechanical engineer) on how to solve this problem that would be great. You can reach me at the office at 801-763-8484. Thanks.

As a quick update I have had a minor improvement in performance by switching out the 22uF capacitor to a 100uF. However a 1000uF capacitor was a bit overkill it seems.

It does appear to work normally with a 47 ohm resistor. Am am going to try a power resistor on par with the DC resistance of the solenoid coil and see how that works.

Otherwise I am looking into getting a high speed schottky type diode into the circuit as opposed to a standard rectifier diode though somehow I have a hard time seeing that as necessary given the very low frequency I am running this device at.

as an update, a 7.5 ohm purely resistive load works decent-ish. There is no noticeable status OK flag flicker though the output on the oscilloscope looks a little bit noisy on the lower end.

This seems to suggest that a schottky diode may do the trick. Looking into that now.

Hello Nathan Macdonald,

Let me try to rephrase your post to see if I understand the situation correctly:

In the .pdf you attached to your previous post, the page labeled “Working circuit” corresponds to a circuit that allows you to operate your proportional solenoid with no visible change in the OK Flag pin state. After about 15 seconds the DRV103 heats up to the point it enters thermal shutdown and the OK flag pin goes low indicating the over-temperature fault.

In the .pdf you attached to your previous post, the page labeled “NOT working circuit” corresponds to a circuit that allows you to operate your proportional solenoid but the OK Flag pin toggles at the PWM frequency indicating that there is an overcurrent fault every time the driver is on. This change in the OK Flag pin only occurs “in the middle of the voltage swing on the potentiometer”. I assume you are referring to the 10 kohm potentiometer referred to as P1 in the “NOT working circuit” page. Is that correct? What ranges of voltage (and duty cycle) are these where the OK Flag pin toggles?

What is the area of the copper plane connected to the DRV103 powerPAD in your SOIC to DIP adapter board?

In one of your posts you wrote “I have had a minor improvement in performance by switching out the 22uF capacitor to a 100uF”. Could you please elaborate as to what the performance improvement was? Depending on what you mean by performance improvement, this change might point to excessive resistance in the power supply connections to the solderless bread board or from the bread board to the DRV103 PCB.

Given that you are using an extremely low PWM frequency setting, the period of time when the driver stays continuously on is higher than in applications where the PWM frequency is higher. Do you have any constraints that would prevent you from trying to operate the DRV103 at higher PWM frequencies?

Best regards,

Jose

There is no appreciable amount of copper plane below the chip in this rough prototype. In the eventual design it will be connected to a massive ground plane and the chip will only be operated intermittently so I expect the heat problems will be gone at that point. In order to adapt the SOIC package to the solderless breadboard I used this part from Digikey: 309-1098-ND. So yes, for now I am rather limited in how long I can have the circuit on continuously but I always shut it off well in advance of when it would shut off due to overheating as I do not want to damage the circuitry.

Otherwise the power supply is an MG model No. PS10AD and I have been running other decent sized loads on this supply without any problems. The connections from the power supply to the bread board are on the order of 0.1 ohms according to my multimeter.

I do have some PWM frquency limitations. The specifications for this proportional solenoid require a maximum driving frequency of 200Hz though after talking to the manufacturer they have had very good success driving it at around 70-100Hz.

Previously the only duty cycle selections that worked properly were 0% and 100%. The noise on the signal was horrendous at basically all duty cycle selections in between and there was flutter on the OK flag pin (indicated via LED). But the OK flag was off once it bumped up to 100% duty cycle.

As noted in the update the circuitry works almost perfectly with a power resistor of the same DC resistance as the coil. The circuitry does not light the OK status indicator (on pin 7) To me this indicates that the noise problem has something to do with the highly inductive load on the chip as opposed to a resistive load of the same size. I suspect that a high speed schottky diode to clamp the reverse EMF on the coil will largely solve the problem but if you have any other ideas I'm all ears.

The performance improvement was a slight reduction on the noise of the output but was otherwise not all that significant.

If you look at that adapter board you will notice exposed vias in the middle which might short out the pins on the circuitry through the thermal transfer pad on the bottom of the IC package. During the soldering process I put a thin layer of insulation over top of those vias thereby eliminating the shorting potential. I confirmed this insulation was working properly by continuity testing all combinations of pins after the chip was fully soldered.

Hello Nathan,

Thank you for the additional information.

I do not have any additional suggestions; I think your test of using a resistive load points to the potential solution by exchanging the diode.

Let me know if further questions arise.

Best regards,

Jose

I finally got a schottky diode into the circuit and it definitively made the difference. The circuit appears to be working properly my all measures now. The waveform is as expected on the oscilloscope and the fault flag stays off.

So to be clear, as noted elsewhere the use of a schottky diode as opposed to a standard rectifier is a non-trivial matter for this chip.