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DRV2700EVM: No output in response to analog input

Dave Sandbach
Prodigy 60 points
Part Number: DRV2700EVM
Other Parts Discussed in Thread: DRV2700, DRV8662

We cannot see high voltage outputs in response to 1.8v pk-pk analog input.  Here's our setup:

  • Powered from USB
  • We're not using the on-board microcontroller, or connection to a PC
  • We want to input a square wave signal at 2.7v peak to peak, at 250Hz. 
  • We are planning to connect a Piezo actuator with 5nF capacitance. No load is currently connected. (NB we have tried connecting a 10nF capacitor, with a 100k resistor across the +/- outputs, without any change in results)
  • Jumpers are configured like this: JP10 to USB, JP11 to USB, JP5 and JP6 open, JP9 JP8 and JP7 to PU, JP13 open, JP12 connected, I2C open. LEDs D3, D4, D5 and D6 are lit.
  • Input signal 0-2.7v sq wave @250Hz connected to AIN terminals

Output voltages with the above configuration measured on the scope are VBST: 0v, OUT-: 0.4v(flat line), OUT+: 0v

We've tried various different configurations without seeing anything over a few mV on the output, including 0 - 2.7v sine wave input directly to TP4, with JP13 connected.  

We have seen the same result now with two boards. We received a third replacement today but I don't want to connect it if we're doing something to kill the board somehow.

Can anyone please help with advice on the configuration we should use?   Thanks

  • 0
    TI__Mastermind 20085 points
    Hi Dave,

    Welcome to E2E, thanks for your interest in our products. We will be responding soon with further information.

    Best Regards
    José Luis Figueroa
    Applications Engineer
  • 0 in reply to José Luis
    Prodigy 60 points

    Thanks José Luis,

    I'm planning to connect our new board according to this setup today (I'm in the UK, so that'll be by around lunchtime in the US).

    After trawling the forums I can't see anything wrong with the setup we're planning to use, so I'm concluding that we must have somehow damaged the boards in our previous setup. We did previously connect an input signal that went negative (+1.5v high state and -1.5v low state) in relation to the in - connection. Do you think that could have caused damage to the board?

    Dave 

  • 0 in reply to Dave Sandbach
    TI__Mastermind 20085 points
    Hi Dave,

    If you mean a periodic input signal (+1.5V high state and -1.5V low state) shouldn't generate any problem. I have reviewed your configuration in our EVM and works properly. I got output peak-peak voltage of 27V in both outputs (Out+ and Out-).
    Make sure that everything is working properly like power supply, input signal, etc.

    Best Regards
    José Luis Figueroa
    Applications Engineer
  • 0 in reply to José Luis
    Prodigy 60 points

    Thank you José Luis,

    I connected the replacement board and it works with this configuration too.  

    I do have another question I hope you can help with - should I start a new thread for this? I'm new on the forum and don't know how to go about it..

    Ideally, I want 120 Vpp or, at least 105 Vpp on the outputs with our Piezo load connected (6nF capacitance).

    At the moment I can only see 75 Vpp, with all the jumpers 2 and 3 and 4 connected. 

    Our input signal is 0v to 2.7v square wave at 250Hz, connected to AIN + and -. 

    Other jumpers are all configured as before.

    Section 6.1 in the full user guide indicates the outputs can be configured for 200 Vpp, but doesn't say how this can be done. 

    Can you please let me know if there's a configuration to drive at 120 Vpp with modifications, or 105 Vpp? 

    Thanks again

  • 0 in reply to Dave Sandbach
    TI__Mastermind 20085 points
    Hi Dave,

    The boost voltage can be programmed as high as 100V. The device must be configured in flyback mode in order to get output voltage higher than 100V. You can refer the Flyback mode, Programming the Boost Voltage and Flyback Circuit sections of the device's datasheet to find further information about this.

    Best Regards
    José Luis Figueroa
    Applications Engineer
  • 0 in reply to José Luis
    TI__Genius 10512 points
    Hi Dave,

    If you want to achieve the differential output voltage of 120Vpp, then you can configure your input signal in single ended mode, section 5.4.
    Or you can use the Piezo Control Console and the PWM inputs switch out of phase to create the differential input signal. If you are just using one input signal from 0V-2.7V on IN+, then you will only see one output switching. You need to create that differential input signal in order to get both outputs switching.
    For 120Vpp, you only need the boost at 70V and the GAIN setting at 34.8V.
  • 0 in reply to José Luis
    Prodigy 60 points

    Thanks again, 

    I now have the 0v-100v output, and we'll experiment with single ended input as suggested in the other post.

  • 0 in reply to Kelly Griffin
    Prodigy 60 points
    Thanks Kelly,

    That looks promising. We'll look into doing it with +/- 1.3v (straight from our processor), or we can increase the (+/-) input voltages if needed.
  • 0 in reply to Dave Sandbach
    Prodigy 60 points

    Thanks again Kelly,

    We did configure the (0v to 2.7v) input as single ended, and changed the gain control as you suggested via the jumpers. The 0v connection for the signal was connected to GND on the DRV2700EVM. This did indeed result in 120 Vpp.

    Unfortunately, it looks like the board can't supply the current our (micro pump) application needs so we're building an alternative solution. But thanks for your help.

    As a non-expert, I found the user guide pretty frustrating for future ref. There are jumpers referred to that aren't on the board (e.g. JP-DC) and the guidance assumes a pretty detailed knowledge of the inner workings of the DRV2700, which I didn't have time to acquire.  I really needed your expert help!

    Thanks again

  • 0 in reply to Dave Sandbach
    TI__Genius 10512 points

    Hi Dave,

    We have a calculation tool for our DRV8662 here; the DRV2700 is nearly identical. This document can be helpful in calculating the current needed for your load and frequency. I'm surprised to hear that the device doesn't have enough current for your pump. Do you need the voltage to be 0V-100V or is the differential voltage ok? I think you need single ended voltage. Our device should be able to drive a 33nF load from 0V-100V up to ~800Hz according to figure 12. We should have plenty of current for 250Hz operation.

    Also I saw that you had a resistor across the outputs. Please remove the resistor; it will only draw extra current.